all in one cisco ccie lab study guide second edition phần 4 doc

1 Add the service timestamps command to RouterA's configuration RouterA(config)#service timestamps On RouterA, monitor the routing table changes with the debug ip route command RouterA#debug ip routing Disconnect the serial line between RouterB and RouterC The following is the output from the debug command Note that after the route was declared invalid, it was placed in holddown, and approximately 30 seconds later, the route was cleared from the table 07:03:18: RT: delete route to 152.1.0.0 via 192.1.1.2, rip metric [120/2] ← Route is declared invalid 07:03:18: RT: no routes to 152.1.0.0, entering holddown ← Route is placed in holddown 07:03:18: 193.1.1.0 in 16 hops (inaccessible) 07:03:18: RT: delete route to 193.1.1.0 via 192.1.1.2, rip metric [120/1] 07:03:18: RT: no routes to 193.1.1.0, entering holddown 07:03:45: RT: garbage collecting entry for 152.1.0.0 ← Route is removed from the routing table 07:03:45: RT: garbage collecting entry for 193.1.1.0 The following is the snapshot of the routing table after the route was declared invalid, but before the route was flushed from the table At this time, the route is marked down and advertised out to all neighbors with a hop count of 16 After the route is flushed from the table, it is no longer advertised to neighboring routers RouterA#sho ip route Codes: C − connected, S − static, I − IGRP, R − RIP, M − mobile, B − BGP D − EIGRP, EX − EIGRP external, O − OSPF, IA − OSPF inter area N1 − OSPF NSSA external type 1, N2 − OSPF NSSA external type E1 − OSPF external type 1, E2 − OSPF external type 2, E − EGP i − IS−IS, L1 − IS−IS level−1, L2 − IS−IS level−2, * − candidate default U − per−user static route, o − ODR Gateway of last resort is not set C C R C R 10.0.0.0/24 is subnetted, subnets 10.1.1.0 is directly connected, Loopback0 148.1.0.0/24 is subnetted, subnets 148.1.1.0 is directly connected, Ethernet0 152.1.0.0/16 is possibly down, routing via 192.1.1.2, Serial0 192.1.1.0/24 is directly connected, Serial0 193.1.1.0/24 is possibly down, routing via 192.1.1.2, Serial0 The following is the output from the debug ip rip command taken during the transition from the invalid to holddown to flushed state: 07:03:18: RIP: received v1 update from 192.1.1.2 on Serial0 07:03:18: 152.1.0.0 in 16 hops (inaccessible) 07:03:18: RIP: sending v1 update to 255.255.255.255 via Ethernet0 (148.1.1.1) 07:03:18: network 10.0.0.0, metric 07:03:18: network 152.1.0.0, metric 16 07:03:18: network 192.1.1.0, metric 07:03:45: RIP: sending v1 update to 255.255.255.255 via Ethernet0 (148.1.1.1) 07:03:45: network 10.0.0.0, metric 07:03:45: network 192.1.1.0, metric Let's examine the data in chronological order using the timestamps At 07:03:18, the route is declared invalid and the holddown counter begins At this time, the route is advertised to all neighbors during the normal update period with a metric of 16 At 07:03:45, approximately 30 seconds after the route was declared invalid, the route is removed from the routing table and is no longer advertised in the normal routing updates 240 Lab #26: Configuring Unicast RIP Updates Equipment Needed The following equipment is needed to perform this lab exercise: • One Cisco router with one Ethernet port • Cisco IOS 10.0 or higher • A PC running a terminal emulation program • One Cisco rolled cable The RIP neighbor command permits the point−to−point (nonbroadcast) exchange of routing information This command can be used in combination with the passive−interface router configuration command to exchange information between a subset of routers and access servers all connected to the same LAN For example, in Figure 6−10, RouterA wishes to only send routing updates to RouterB on the Ethernet LAN Since RIP is a broadcast protocol, by default, it will send updates to all devices on the Ethernet LAN To prevent this from happening, RouterA's Ethernet interface is configured as passive However, in this case, a neighbor router configuration command is included This command permits the sending of routing updates to a specific neighbor One copy of the routing update is generated per defined neighbor Figure 6−10: RIP Unicast updates Router Configurations The configuration for RouterA is as follows (key RIP configurations for RouterA are highlighted in bold) RouterA Building configuration Current configuration: ! version 11.2 no service password−encryption no service udp−small−servers no service tcp−small−servers ! hostname RouterA ! interface Loopback0 ip address 1.1.1.1 255.255.255.0 ! interface Ethernet0 ip address 192.1.1.1 255.255.255.0 no keepalive ← Disables the keepalive on the Ethernet interface, allows the interface to stay up when it is not attached to a hub ! ! router rip ← Enables the RIP routing process on the router passive−interface Ethernet0 ← Disables the sending of RIP updates on interface 241 Ethernet network 192.1.1.0 ← Specifies what interfaces will receive and send RIP routing updates It also specifies what networks will be advertised network 1.1.1.1 neighbor 192.1.1.2 ← Permits the point−to−point (nonbroadcast) exchange of routing information ! no ip classless ! line line aux line vty login ! end Monitoring and Testing the Configuration The following is the output from the debug ip rip command Note that RIP updates are being sent to the Unicast address 192.1.1.2 on Ethernet and the broadcast address 255.255.255.255 on interface loopback RouterA#debug ip rip RIP: sending v1 update to 255.255.255.255 via Loopback0 (1.1.1.1) network 192.1.1.0, metric RIP: sending v1 update to 192.1.1.2 via Ethernet0 (192.1.1.1) network 1.0.0.0, metric Lab #27: RIP and Discontiguous Networks Equipment Needed The following equipment is needed to perform this lab exercise: • Two Cisco routers with one Ethernet port and one serial port • Cisco IOS 10.0 or higher • A PC running a terminal emulation program • One Cisco rolled cable A discontiguous network is a network that has subnets of the same major network separated by another major network For example, in Figure 6−11, network 130.1.1.0/24 on RouterA is separated from network 130.1.2.0/24 on RouterB by the major network 131.1.1.0 Figure 6−11: Discontiguous networks Due to the classful nature of RIP and the fact that no mask information is carried in the routing updates, support for discontiguous networks becomes a problem For example, in Figure 6−11, when the RouterA sends updates for network 130.1.1.0 to RouterB, it summarizes the network at the natural class — in this case, class B (130.1.0.0) When RouterB receives an updated advertising network 130.1.0.0, it drops the update because one of its own interfaces is connected to network 130.1.0.0 The router will not accept an update for a network to which its own interface is connected The solution to this problem is to add a secondary address to the interfaces connecting RouterA to RouterB The secondary address should be in the same major network as the discontiguous network and use the same 242 subnet mask As shown in Figure 6−12, with the addition of the secondary address, the networks are no longer discontiguous Figure 6−12: Secondary address is used to support discontiguous networks This configuration will demonstrate the use of secondary addresses to eliminate discontiguous networks across a RIP network RouterA and RouterB are connected serially via a crossover cable RouterA will act as the DCE supplying clock to RouterB The IP addresses are assigned as per Figure 6−11 All routers will be configured for RIP and advertise all connected networks Router Configurations The configuration for RouterA is as follows (key RIP configurations are highlighted in bold) RouterA Current configuration: ! version 12.0 service timestamps debug uptime service timestamps log uptime no service password−encryption ! hostname RouterA ! ip subnet−zero ! interface Ethernet0/0 ip address 130.1.1.1 255.255.255.0 no ip directed−broadcast no keepalive ← Disables the keepalive on the Ethernet interface, allows the interface to stay up when it is not attached to a hub ! interface Serial0/0 ip address 131.1.1.1 255.255.255.0 no ip directed−broadcast no ip mroute−cache clockrate 1000000 ← Acts as DCE providing clock ! router rip ← Enables the RIP routing process on the router network 130.1.0.0 network 131.1.0.0 ← Specifies what interfaces will receive and send RIP routing updates It also specifies what networks will be advertised ! ip classless no ip http server ! line transport input none line aux line vty ! RouterB Current configuration: ! 243 version 12.0 service timestamps debug uptime service timestamps log uptime no service password−encryption ! hostname RouterB ! ip subnet−zero ! interface Ethernet0/0 ip address 130.1.2.1 255.255.255.0 no ip directed−broadcast no keepalive ← Disables the keepalive on the Ethernet interface, allows the interface to stay up when it is not attached to a hub ! interface Serial0/0 ip address 131.1.1.2 255.255.255.0 no ip directed−broadcast no ip mroute−cache no fair−queue ! router rip ← Enables the RIP routing process on the router network 130.1.0.0 network 131.1.0.0 ← Specifies what interfaces will receive and send RIP routing updates It also specifies what networks will be advertised ! ip classless no ip http server ! line transport input none line aux line vty ! Monitoring and Testing the Configuration Enable RIP update debugging on RouterB with the command debug ip rip The following is the output from the command Notice that RouterB is receiving an update from RouterA for network 130.1.0.0 As mentioned earlier, when an update is sent across a network boundary (in this case, network 131.1.0.0), it is summarized at the natural class mask RouterB# 00:43:19: RIP: received v1 update from 131.1.1.1 on Serial0/0 00:43:19: 130.1.0.0 in hops Display the routing table on RouterB with the command show ip route The following is the output Notice that RouterB does not have an entry for network 130.1.1.0 in its routing table When RouterB receives the update for network 130.1.0.0, it drops it because it has a direct connection to the same network RouterB#show ip route Codes: C − connected, S − static, I − IGRP, R − RIP, M − mobile, B − BGP D − EIGRP, EX − EIGRP external, O − OSPF, IA − OSPF inter area N1 − OSPF NSSA external type 1, N2 − OSPF NSSA external type E1 − OSPF external type 1, E2 − OSPF external type 2, E − EGP i − IS−IS, L1 − IS−IS level−1, L2 − IS−IS level−2, ia − IS−IS inter area * − candidate default, U − per−user static route, o − ODR P − periodic downloaded static route Gateway of last resort is not set C 130.1.0.0/24 is subnetted, subnets 130.1.2.0is directly connected, Ethernet0/0 131.1.0.0/24 is subnetted, subnets 244 C 131.1.1.0is directly connected, Serial0/0 The solution to this problem is to add a secondary address to the interfaces connecting RouterA to RouterB The secondary address should be in the same major network as the discontiguous network and use the same subnet mask As shown in Figure 6−12, add a secondary address to the serial interface of RouterA and RouterB The following commands add a secondary IP address to the serial interface of RouterA and RouterB: RouterA#conf terminal RouterA(config)#interface s0/0 RouterA(config−if)#ip address 130.1.3.1 255.255.255.0 secondary RouterB#conf terminal RouterB(config)#interface s0/0 RouterB(config−if)#ip address 130.1.3.2 255.255.255.0 secondary Enable RIP update debugging on RouterB with the command debug ip rip The following is the output from the command Notice that RouterB is now receiving an update from RouterA for network 130.1.1.0 Since the update is no longer being sent across a network boundary, it is not summarized at the natural class mask 00:59:03: RIP: received v1 update from 130.1.3.1 on Serial0/0 00:59:03: 130.1.1.0 in hops Display the routing table on RouterB with the command show ip route The following is the output Notice that there is now an entry for network 130.1.1.0 in its routing table RouterB#show ip route Codes: C − connected, S − static, I − IGRP, R − RIP, M − mobile, B − BGP D − EIGRP, EX − EIGRP external, O − OSPF, IA − OSPF inter area N1 − OSPF NSSA external type 1, N2 − OSPF NSSA external type E1 − OSPF external type 1, E2 − OSPF external type 2, E − EGP i − IS−IS, L1 − IS−IS level−1, L2 − IS−IS level−2, ia − IS−IS inter area * − candidate default, U − per−user static route, o − ODR P − periodic downloaded static route Gateway of last resort is not set C C R R R C 130.1.0.0/24 130.1.3.0 130.1.2.0 130.1.1.0 130.1.0.0 131.1.0.0/24 131.1.0.0 131.1.1.0 is subnetted, subnets is directly connected, Serial0/0 is directly connected, Ethernet0/0 [120/1] via 130.1.3.1, 00:00:25, Serial0/0 [120/1] via 131.1.1.1, 00:00:25, Serial0/0 is subnetted, subnets [120/1] via 130.1.3.1, 00:00:25, Serial0/0 is directly connected, Serial0/0 Troubleshooting RIP The Cisco IOS provides many tools for troubleshooting routing protocols The following is a list of key commands along with a sample output from each that will aid in troubleshooting RIP {debug ip rip} This exec command displays information on RIP routing transactions The output shows whether the router is sending or receiving an update, the networks contained in the update, and the metric or hop count for each RIP: sending v1 update to 255.255.255.255 via Ethernet0 (148.1.1.1) network 10.0.0.0, metric network 192.1.1.0, metric network 148.1.0.0, metric RIP: received v1 update from 192.1.1.2 on Serial0 193.1.1.0 in hops 245 {debug ip routing} This exec command displays information on routing table updates The output shows what routes have been added or deleted, and for the distance vector routing protocols, what routes are in holddown RT: delete route to 152.1.0.0 via 192.1.1.2, rip metric [120/2] RT: no routes to 152.1.0.0, entering holddown RT: delete route to 193.1.1.0 via 192.1.1.2, rip metric [120/1] RT: no routes to 193.1.1.0, entering holddown RT: add 193.1.1.0/24 via 192.1.1.2, rip metric [120/1] {show ip protocol} This exec command displays the parameters and current state of the active routing protocol process The output shows the routing protocol used, timer information, inbound and outbound filter information, protocols being redistributed, and the networks that the protocol is routing for This command is very useful for troubleshooting a router that is sending bad router updates RouterA#show ip protocols Routing Protocol is "rip" Sending updates every seconds, next due in seconds Invalid after 15 seconds, hold down 15, flushed after 30 Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Redistributing: rip Default version control: send version 1, receive any version Interface Send Recv Key−chain Ethernet0 1 Loopback0 1 Serial0 1 Routing for Networks: 10.0.0.0 192.1.1.0 148.1.0.0 Routing Information Sources: Gateway Distance Last Update 192.1.1.2 120 00:00:01 Distance: (default is 120) {show ip route rip} This exec command quickly displays all of the routes learned via RIP This is a quick way to verify that a router is receiving RIP updates RouterA#show ip route rip R 152.1.0.0/16 [120/2] via 192.1.1.2, 00:00:00, Serial0 R 193.1.1.0/24 [120/1] via 192.1.1.2, 00:00:00, Serial0 Conclusion RIP is the most widely used Interior Gateway Routing Protocol (IGRP) in large organizations today, especially in organizations that have a large UNIX−based routing environment However, it is worth noting the limitations one faces when deploying a large RIP network: • RIP uses a 4−bit metric to count router hops to destinations This limits the size of a RIP network, which cannot contain more than 15 hops to a destination This is a severe limitation when trying to implement a typical modern large−scale network • RIP uses hop count as a routing metric, which does provide the most optimal path selection More advanced protocols like IGRP use complex metrics to determine the optimal path • RIP was deployed prior to subnetting and has no direct subnet support RIP assumes that all interfaces on the network have the same mask • RIP broadcasts a complete list of networks that it can reach every 30 seconds by default This can amount to a significant amount of traffic, especially on low−speed links 246 • RIP has no security features built in A RIP−enabled device will accept RIP updates from any other device on the network More modern routing protocols, such as OSPF, enable the router to authenticate updates 247 Chapter 7: Interior Gateway Routing Protocol Overview Topics Covered in This Chapter • Detailed technology overview • Mechanisms to prevent routing loops • IGRP route types • Basic IGRP configuration • Passive Interfaces • IGRP unequal−cost load balancing • IGRP Unicast updates • IGRP timer configurations • Detailed troubleshooting examples Introduction Interior Gateway Routing Protocol (IGRP) is a Cisco proprietary distance vector routing protocol developed in 1986 to address the limitations of RIP Although RIP works quite well in small homogenous internetworks, its small hop count (16) severely limits the size of the network and its single metric (hop count) does not provide the routing flexibility needed in complex networks IGRP addresses the shortcomings of RIP by allowing the network to grow up to 255 hops and by providing a wide range of metrics (link reliability, bandwidth, internetwork delay, and load) to provide routing flexibility in today's complex networks Technology Overview Routing Loops The problem with a first− or second−generation distance vector routing protocol like IGRP is that each router does not have a complete view of the network Routers must rely on the neighboring routers for network reachability information, thus creating a slow convergence problem in which inconsistencies arise because routing update messages propagate slowly across the network To reduce the likelihood of routing loops caused by inconsistencies across the network, IGRP uses the following mechanisms: split horizons, poison reverse updates, holddown counters, and flash updates Split Horizon The rule of split horizon states that it is never useful for a router to advertise a route back in the direction from which it came When split horizons is enabled on a router's interface, the router records the interface over which a route was received and does not propagate information about that route back out that interface The Cisco router allows you to disable split horizons on a per−interface basis This is sometimes necessary in NBMA (Non Broadcast Multiple Access) hub and spoke environments In Figure 7−1, RouterB is connected to RouterC and RouterA via Frame Relay, both PVCs terminating on one physical interface on RouterB 248 Figure 7−1: Split horizons In Figure 7−1, if split horizon is not disabled on RouterB's Serial interface, then RouterC will not receive RouterA's routing advertisements and vice versa Use the no ip split−horizon interface subcommand to disable split horizons Poison Reverse Split horizon is a scheme used by the router to avoid problems caused by advertising routes back to the router from which they were learned The split horizon scheme omits routes learned from one neighbor in updates sent to that neighbor Split horizon with poison reverse includes the routes in updates but sets the metric to 4294967295 When a router sees increases in routing metrics, it generally indicates a routing loop The router then sends poison reverse updates to remove the route and place it in holddown In Cisco's implementation of IGRP, poison reverse updates are sent if a route metric has increased by a factor of 1.1 or greater By setting the hop count to max and advertising the route back to its source, it is possible to immediately break a routing loop Otherwise, the inaccurate route will stay in the routing table until it times out The disadvantage to poison reverse is that it increases the size of the routing table Holddown Holddown timers prevent the router from accepting routing information about a network for a fixed period of time after the route has been removed from the routing table The idea is to make sure all routers have received the information, and no router sends out an invalid route For example, in Figure 7−2 RouterB advertises bad information to RouterC because of the delay in the routing update Holddown counters would prevent this from happening because RouterC would not install a new route to NetworkA for 280 seconds By then RouterB would have converged with the proper routing information Figure 7−2: Routing loop 249 Show the status of the OSPF neighbors on RouterA with the command show ip ospf neighbor Notice that RouterA is fully adjacent with RouterB (2.2.2.2), which is the DR for the network RouterA#show ip ospf neighbor Neighbor ID 2.2.2.2 Pri State FULL/DR Dead Time 00:01:42 Address 192.1.1.2 Interface Serial0/0 Show the IP routing table on RouterA with the command show ip route; note that RouterA has a route to the loopback addresses on RouterB and RouterC After the destination address are two numbers 110/65 The 110 is the administrative distance of OSPF, which is used to compare multiple routes to the same destination The lower the administrative distance, the more trustworthy the route is For example, RIP has an administrative distance of 120, so if RouterA learned the same route from RIP and OSPF, the OSPF route is preferred because it has the lower administrative distance The second number, 65, is the metric or cost of using the route This is used to compare routes that are learned via the same routing protocol; the route with the lowest cost is preferred RouterA#show ip route Codes: C − connected, S − static, I − IGRP, R − RIP, M − mobile, B − BGP D − EIGRP, EX − EIGRP external, O − OSPF, IA − OSPF inter area N1 − OSPF NSSA external type 1, N2 − OSPF NSSA external type E1 − OSPF external type 1, E2 − OSPF external type 2, E − EGP i − IS−IS, L1 − IS−IS level−1, L2 − IS−IS level−2, * − candidate default U − per−user static route, o − ODR Gateway of last resort is not set C O O C 1.0.0.0/24 is subnetted, subnets 1.1.1.0 is directly connected, Loopback0 2.0.0.0/32 is subnetted, subnets 2.2.2.2 [110/65] via 192.1.1.2, 00:02:22, Serial0/0 3.0.0.0/32 is subnetted, subnets 3.3.3.3 [110/65] via 192.1.1.3, 00:02:22, Serial0/0 192.1.1.0/24 is directly connected, Serial0/0 Display the status of the OSPF neighbors on RouterB with the command show ip ospf neighbor Notice that RouterB has two neighbors, RouterA (1.1.1.1) and RouterC (3.3.3.3), and has formed a full adjacency with each RouterB was elected DR for the network because it has the highest priority The DR and BDR form full adjacencies with every other router On a non−broadcast network, the DR and BDR are the only routers that need to define neighbors RouterB#show ip ospf neighbor Neighbor ID 3.3.3.3 1.1.1.1 Pri 0 State FULL/DROTHER FULL/DROTHER Dead Time 00:01:55 00:01:43 Address 192.1.1.3 192.1.1.1 Interface Serial0/0 Serial0/0 Display the status of the OSPF neighbors on RouterC with the command show ip ospf neighbor Notice that RouterC has only one neighbor, RouterB, which is the DR for the network No BDR was elected for the network because RouterB was the only router that had a nonzero OSPF priority If the OSPF priority of a router is zero, then it cannot be elected the DR or BDR RouterC#show ip ospf neighbor Neighbor ID 192.1.1.2 Pri State FULL/DR Dead Time 00:01:37 Address 192.1.1.2 Interface Serial0/0 In an NBMA network, care must be taken to assure a full mesh topology or static selection of the DR using interface priority For this lab topology, it is imperative that RouterB's serial interface becomes the DR 314 because it is the only router that has full connectivity to all other routers Let's see what would happen when RouterA becomes the DR for the network Change the OSPF priority on RouterB and remove the neighbor statements with the following commands RouterB#configure terminal RouterB(config)#interface s0/0 RouterB(config−if)#ip ospf priority RouterB(config−if)#router ospf 64 RouterB(config−router)#no neighbor 192.1.1.1 RouterB(config−router)#no neighbor 192.1.1.3 Change the OSPF priority of RouterA's serial interface to 10 and add a neighbor statement for RouterB and RouterC with the following command RouterA#configure terminal RouterA(config)#interface s0 RouterA(config−if)#ip ospf priority 10 RouterA(config−if)#router ospf 64 RouterA(config−router)#neighbor 192.1.1.2 RouterA(config−router)#neighbor 192.1.1.3 Make sure the configurations are written to NVRAM and reload the routers The reason the routers need to be reloaded is that, once a DR is elected for the network, no other router can become the DR until the DR is dead From RouterA, show the OSPF interface statistics with the command show ip ospf interface s0/0 Notice that RouterA (1.1.1.1) is now the DR for the network RouterA#show ip ospf interface s0 Serial0 is up, line protocol is up Internet Address 192.1.1.1/24, Area Process ID 64, Router ID 1.1.1.1, Network Type NON_BROADCAST, Cost: 64 Transmit Delay is sec, State DR, Priority 10 Designated Router (ID) 1.1.1.1, Interface address 192.1.1.1 No backup designated router on this network Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit Hello due in 00:00:01 Neighbor Count is 1, Adjacent neighbor count is Adjacent with neighbor 2.2.2.2 Display the status of the OSPF neighbors on RouterC with the command show ip ospf neighbor Notice that RouterA has only formed an adjacency with RouterB (2.2.2.2) but not RouterC This is because it only has physical connectivity to RouterB; the DR must have physical connectivity to all routers on the network RouterA#show ip ospf neighbor Neighbor ID N/A 2.2.2.2 Pri 0 State ATTEMPT/DROTHER FULL/DROTHER Dead Time − 00:01:55 Address 192.1.1.3 192.1.1.2 Interface Serial0 Serial0 Display the routing table on RouterC; notice there are no routes This is because RouterC was unable to form an adjacency with the DR RouterC#show ip route Codes: C − connected, S − static, I − IGRP, R − RIP, M − mobile, B − BGP D − EIGRP, EX − EIGRP external, O − OSPF, IA − OSPF inter area N1 − OSPF NSSA external type 1, N2 − OSPF NSSA external type E1 − OSPF external type 1, E2 − OSPF external type 2, E − EGP i − IS−IS, L1 − IS−IS level−1, L2 − IS−IS level−2, * − candidate default U − per−user static route, o − ODR 315 Gateway of last resort is not set C C 3.0.0.0/24 is subnetted, subnets 3.3.3.0 is directly connected, Loopback0 192.1.1.0/24 is directly connected, Serial0 Lab #38: Configuring OSPF on NBMA Network "Broadcast Model" Equipment Needed The following equipment is needed to perform this lab exercise: • Three Cisco routers, each having one serial port • One Cisco router with three serial ports acting as a frame relay switch • Cisco IOS 10.0 or higher • A PC running a terminal emulation program • Three Cisco V.35 DCE/DTE crossover cables • Cisco rolled cable for console port access Overview The broadcast network type is a workaround for having to define all neighbors statically When an interface is configured for broadcast, it will behave as if it were connected to a LAN A DR and BDR will still be elected for the network, so care must be taken to assure that the router elected DR/BDR has physical connectivity to all routers on the network Configuration Overview This lab will demonstrate configuring OSPF over Frame Relay using the broadcast network type RouterA, RouterB, and RouterC will connect serially via a crossover cable to a Cisco router (FrameSwitch), which will act as a frame relay switch The FrameSwitch will act as the DCE supplying clock for all attached routers; detailed documentation on configuring a Cisco router as a frame relay switch can be found in Chapter The network type will be set on all routers using the interface command ip ospf network broadcast The IP addresses are as per Figure 8−12; RouterA and RouterC serial interfaces will be configured with an OSPF priority of This will ensure that RouterB becomes the DR for the network Figure 8−12: Configuring OSPF on NBMA network Router Configurations The configurations for the routers in this example are as follows (key OSPF commands are highlighted in bold) 316 FrameSwitch : ! version 11.2 no service udp−small−servers no service tcp−small−servers ! hostname FrameSwitch ! ! frame−relay switching ! interface Ethernet0/0 no ip address shutdown ! interface Serial0/0 no ip address encapsulation frame−relay IETF no fair−queue clockrate 500000 frame−relay lmi−type ansi frame−relay intf−type dce frame−relay route 100 interface ! interface Serial0/1 no ip address encapsulation frame−relay IETF clockrate 500000 frame−relay lmi−type ansi frame−relay intf−type dce frame−relay route 100 interface frame−relay route 200 interface ! interface Ethernet1/0 no ip address shutdown ! interface Serial1/0 no ip address encapsulation frame−relay IETF clockrate 500000 frame−relay lmi−type ansi frame−relay intf−type dce frame−relay route 200 interface ! no ip classless ! ! line line aux line vty login ! end Serial0/1 100 Serial0/0 Serial1/0 100 200 Serial0/1 200 RouterA version 11.2 no service udp−small−servers no service tcp−small−servers ! hostname RouterA ! ! 317 interface Loopback0 ← Defines a virtual interface the IP address is used as the router ID ip address 1.1.1.1 255.255.255.0 ! interface Ethernet0/0 no ip address shutdown ! interface Serial0/0 ip address 192.1.1.1 255.255.255.0 encapsulation frame−relay IETF ip ospf network broadcast ← Defines the network type as broadcast ip ospf priority ← Sets the priority used by the router in DR election for a particular interface An OSPF priority of zero means that the router is ineligible in the DR election process frame−relay map ip 192.1.1.2 100 broadcast frame−relay map ip 192.1.1.3 100 broadcast frame−relay lmi−type ansi ! interface Serial1/0 no ip address shutdown ! ! router ospf 64 ← Enables OSPF process 64 on the router network 192.1.1.0 0.0.0.255 area ← Specifies what interface OSPF will be run on and what area the interface will be in network 1.1.1.1 0.0.0.0 area ! no ip classless ! line line aux line vty login ! end RouterB version 11.2 no service udp−small−servers no service tcp−small−servers ! hostname RouterB ! interface Loopback0 ← Defines a virtual interface the IP address is used as the router ID ip address 2.2.2.2 255.255.255.0 ! interface Ethernet0/0 no ip address shutdown ! interface Serial0/0 ip address 192.1.1.2 255.255.255.0 encapsulation frame−relay IETF ip ospf network broadcast ← Defines the network type as broadcast frame−relay map ip 192.1.1.1 100 broadcast frame−relay map ip 192.1.1.3 200 broadcast frame−relay lmi−type ansi ! interface Serial0/1 no ip address 318 shutdown ! router ospf 64 ← Enables OSPF process 64 on the router network 192.1.1.0 0.0.0.255 area ← Specifies what interface OSPF will be run on and what area the interface will be in network 2.2.2.2 0.0.0.0 area ! no ip classless ! ! line line aux line vty login ! end RouterC ! version 11.2 no service udp−small−servers no service tcp−small−servers ! hostname RouterC ! ! interface Loopback0 ← Defines a virtual interface the IP address is used as the router ID ip address 3.3.3.3 255.255.255.0 ! interface Ethernet0/0 no ip address shutdown ! interface Serial0/0 ip address 192.1.1.3 255.255.255.0 encapsulation frame−relay IETF ip ospf network broadcast ← Defines the network type as broadcast ip ospf priority ← Sets the priority used by the router in DR election for a particular interface An OSPF priority of zero means that the router is ineligible in the DR election process frame−relay map ip 192.1.1.1 200 broadcast frame−relay map ip 192.1.1.2 200 broadcast frame−relay lmi−type ansi ! interface Serial0/1 no ip address shutdown ! ! router ospf 64 ← Enables OSPF process 64 on the router network 192.1.1.0 0.0.0.255 area network 3.3.3.3 0.0.0.0 area ! no ip classless ! ! line line aux line vty login ! 319 end Monitoring and Testing the Configuration From RouterA, show the OSPF interface statistics with the command show ip ospf interface s0/0 Notice that the interface is network type broadcast, which means that a DR is elected Since the network is broadcast, no neighbors need to be defined The priority of the interface is 0, which means that it is ineligible to be elected the DR or BDR for the network RouterA#show ip ospf interface s0/0 Serial0 is up, line protocol is up Internet Addr\ess 192.1.1.1/24, Area Process ID 64, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 64 Transmit Delay is sec, State DROTHER, Priority Designated Router (ID) 2.2.2.2, Interface address 192.1.1.2 No backup designated router on this network Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit Hello due in 00:00:01 Neighbor Count is 1, Adjacent neighbor count is Adjacent with neighbor 2.2.2.2 (Designated Router) Show the status of the OSPF neighbors on RouterA with the command show ip ospf neighbor Notice that RouterA is fully adjacent with RouterB (2.2.2.2), which is the DR for the network RouterA#show ip ospf neighbor Neighbor ID 2.2.2.2 Pri State FULL/DR Dead Time 00:00:34 Address 192.1.1.2 Interface Serial0 Show the status of the OSPF neighbors on RouterB with the command show ip ospf neighbor Notice that RouterB is fully adjacent with RouterA (1.1.1.1) and RouterC (3.3.3.3) Both routers are DROTHER, which means that they are neither the DR nor the BDR for the network RouterB#show ip ospf neighbor Neighbor ID 3.3.3.3 1.1.1.1 Pri 0 State FULL/DROTHER FULL/DROTHER Dead Time 00:00:34 00:00:35 Address 192.1.1.3 192.1.1.1 Interface Serial0 Serial0 Let's see what would happen when RouterA becomes the DR and RouterB becomes the BDR for the network Change the OSPF priority on RouterB with the following commands RouterB#configure terminal RouterB(config)#interface s0/0 RouterB(config−if)#ip ospf priority Change the OSPF priority of RouterA's serial interface to 10 with the following command RouterA#configure terminal RouterA(config)#interface s0 RouterA(config−if)#ip ospf priority 10 Make sure the configurations are written to NVRAM and reload the routers The reason the routers need to be reloaded is that, once a DR is elected for the network, no other router can become the DR until the DR is dead From RouterA, show the OSPF interface statistics with the command show ip ospf interface s0/0 Notice that RouterA is now the DR and RouterB is the BDR for the network 320 RouterA#show ip ospf interface s0 Serial0 is up, line protocol is up Internet Address 192.1.1.1/24, Area Process ID 64, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 64 Transmit Delay is sec, State DR, Priority 10 Designated Router (ID) 1.1.1.1, Interface address 192.1.1.1 Backup Designated router (ID) 2.2.2.2, Interface address 192.1.1.2 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit Hello due in 00:00:05 Neighbor Count is 1, Adjacent neighbor count is Adjacent with neighbor 2.2.2.2 (Backup Designated Router) Show the status of the OSPF neighbors on RouterB with the command show ip ospf neighbor Notice that RouterB is fully adjacent with RouterA (1.1.1.1) and RouterC (3.3.3.3) RouterA is the DR for the network and RouterC is DROTHER RouterB#show ip ospf neighbor Neighbor ID 3.3.3.3 1.1.1.1 Pri 10 State FULL/DROTHER FULL/DR Dead Time 00:00:34 00:00:36 Address 192.1.1.3 192.1.1.1 Interface Serial0 Serial0 Show the status of the OSPF neighbors on RouterC with the command show ip ospf neighbor Notice that RouterC thinks that RouterB is the DR for the network; this is because RouterC does not have a physical connection to the RouterA RouterC#show ip ospf neighbor Neighbor ID Pri State 2.2.2.2 FULL/DR Dead Time 00:00:31 Address 192.1.1.2 Interface Serial0 Let's take a look at the OSPF database on RouterC with the command show ip ospf database This command shows the table of link state advertisements the router uses as input to the Dijkstra algorithm to determine the routing table Notice that RouterC has the links 1.1.1.1 and 2.2.2.2, which are the loopback interfaces on RouterA and RouterB, respectively RouterC#show ip ospf database OSPF Router with ID (3.3.3.3) (Process ID 64) Router Link States (Area 0) Link ID ADV Router Age Seq# 1.1.1.1 1.1.1.1 663 0x80000003 2.2.2.2 2.2.2.2 662 0x80000003 3.3.3.3 3.3.3.3 665 0x80000003 Net Link States (Area 0) Link ID ADVRouter Age Seq# 192.1.1.1 1.1.1.1 663 0x80000001 Checksum 0xB4B8 0xC27D 0xC869 Link count 2 Checksum 0xFE87 Show the routing table on RouterC with the command show ip route Notice that there is not a route to 1.1.1.1 or 2.2.2.2 RouterC#show ip route Codes: C − connected, S − static, I − IGRP, R − RIP, M − mobile, B − BGP D − EIGRP, EX − EIGRP external, O − OSPF, IA − OSPF inter area N1 − OSPF NSSA external type 1, N2 − OSPF NSSA external type E1 − OSPF external type 1, E2 − OSPF external type 2, E − EGP i − IS−IS, L1 − IS−IS level−1, L2 − IS−IS level−2, * − candidate default U − per−user static route, o − ODR Gateway of last resort is not set C C 3.0.0.0/24 is subnetted, subnets 3.3.3.0 is directly connected, Loopback0 192.1.1.0/24 is directly connected, Serial0 321 This is because the advertising router the DR for the broadcast network (RouterA) is not reachable This can be seen from the command show ip ospf database router on RouterC RouterC#show ip ospf database router OSPF Router with ID (3.3.3.3) (Process ID 64) Router Link States (Area 0) Adv Router is not−reachable LS age: 63 Options: (No TOS−capability, No DC) LS Type: Router Links Link State ID: 1.1.1.1 Advertising Router: 1.1.1.1 LS Seq Number: 80000004 Checksum: 0xB2B9 Length: 48 Number of Links: Link connected to: a Stub Network (Link ID) Network/subnet number: 1.1.1.1 (Link Data) Network Mask: 255.255.255.255 Number of TOS metrics: TOS Metrics: Link connected to: a Transit Network (Link ID) Designated Router address: 192.1.1.1 (Link Data) Router Interface address: 192.1.1.1 Number of TOS metrics: TOS Metrics: 64 Lab #39: Configuring OSPF on NBMA Network "Point−to−Multipoint Model" Equipment Needed The following equipment is needed to perform this lab exercise: • Three Cisco routers, each having one serial port • One Cisco router with three serial ports acting as a frame relay switch • Cisco IOS 10.0 or higher • A PC running a terminal emulation program • Three Cisco V.35 DCE/DTE crossover cables • Cisco rolled cable for console port access Overview A point−to−multipoint network type is treated as a numbered point−to−point interface having one or more neighbors When an interface is configured for point−to−multipoint, no DR/BDR are elected and neighbors not need to be defined, greatly simplifying configuring OSPF over an NBMA network Configuration Overview This lab will demonstrate configuring OSPF over Frame Relay using the point−to−multipoint network type RouterA, RouterB, and RouterC will connect serially via a crossover cable to a Cisco router (FrameSwitch), which will act as a frame relay switch 322 The FrameSwitch will act as the DCE supplying clock for all attached routers; detailed documentation on configuring a Cisco router as a frame relay switch can be found in Chapter The network type will be set on all routers using the interface command ip ospf network point−to−multipoint The IP addresses are as per Figure 8−13; no neighbors need to be defined and OSPF priorities need not be set since DR/BDR is not elected for the network Figure 8−13: Physical connectivity Router Configurations The configurations for the routers in this example are as follows (key OSPF commands are highlighted in bold) FrameSwitch version 11.2 no service udp−small−servers no service tcp−small−servers ! hostname FrameSwitch ! ! frame−relay switching ! interface Ethernet0/0 no ip address shutdown ! interface Serial0/0 no ip address encapsulation frame−relay IETF no fair−queue clockrate 500000 frame−relay lmi−type ansi frame−relay intf−type dce frame−relay route 100 interface Serial0/1 ! interface Serial0/1 no ip address encapsulation frame−relay IETF clockrate 500000 frame−relay lmi−type ansi frame−relay intf−type dce frame−relay route 100 interface Serial0/0 frame−relay route 200 interface Serial1/0 ! interface Ethernet1/0 no ip address shutdown ! interface Serial1/0 no ip address encapsulation frame−relay IETF clockrate 500000 frame−relay lmi−type ansi 100 100 200 323 frame−relay intf−type dce frame−relay route 200 interface Serial0/1 200 ! no ip classless ! ! line line aux line vty login ! end RouterA version 11.2 no service udp−small−servers no service tcp−small−servers ! hostname RouterA ! ! interface Loopback0 ← Defines a virtual interface the IP address is used as the router ID ip address 1.1.1.1 255.255.255.0 ! interface Ethernet0/0 no ip address shutdown ! interface Serial0/0 ip address 192.1.1.1 255.255.255.0 encapsulation frame−relay IETF ip ospf network point−to−multipoint ← Defines the network type as point−to− multipoint frame−relay map ip 192.1.1.2 100 broadcast frame−relay map ip 192.1.1.3 100 broadcast frame−relay lmi−type ansi ! interface Serial1/0 no ip address shutdown ! ! router ospf 64 ← Enables OSPF process 64 on the router network 192.1.1.0 0.0.0.255 area ← Specifies what interface OSPF will be run on and what area the interface will be in network 1.1.1.1 0.0.0.0 area ! no ip classless ! line line aux line vty login ! end RouterB version 11.2 no service udp−small−servers no service tcp−small−servers ! hostname RouterB 324 ! ! interface Loopback0 ← Defines a virtual interface the IP address is used as the router ID ip address 2.2.2.2 255.255.255.0 ! interface Ethernet0/0 no ip address shutdown ! interface Serial0/0 ip address 192.1.1.2 255.255.255.0 encapsulation frame−relay IETF ip ospf network point−to−multipoint ← Defines the network type as point−to− multipoint frame−relay map ip 192.1.1.1 100 broadcast frame−relay map ip 192.1.1.3 200 broadcast frame−relay lmi−type ansi ! interface Serial0/1 no ip address shutdown ! router ospf 64 ← Enables OSPF process 64 on the router network 192.1.1.0 0.0.0.255 area ← Specifies what interface OSPF will be run on and what area the interface will be in network 2.2.2.2 0.0.0.0 area ! no ip classless ! ! line line aux line vty login ! end RouterC ! version 11.2 no service password−encryption no service udp−small−servers no service tcp−small−servers ! hostname RouterC ! ! interface Loopback0 ← Defines a virtual interface the IP address is used as the router ID ip address 3.3.3.3 255.255.255.0 ! interface Ethernet0/0 no ip address shutdown ! interface Serial0/0 ip address 192.1.1.3 255.255.255.0 encapsulation frame−relay IETF ip ospf network point−to−multipoint ← Defines the network type as point−to− multipoint frame−relay map ip 192.1.1.1 200 broadcast frame−relay map ip 192.1.1.2 200 broadcast 325 frame−relay lmi−type ansi ! interface Serial0/1 no ip address shutdown ! ! router ospf 64 ← Enables OSPF process 64 on the router network 192.1.1.0 0.0.0.255 area network 3.3.3.3 0.0.0.0 area ! no ip classless ! ! line line aux line vty login ! end Monitoring and Testing the Configuration From RouterA, show the OSPF interface statistics with the command show ip ospf interface s0/0 Notice that the interface is network type POINT_TO_MULTIPOINT, which means that a DR/BDR is elected and no neighbors need to be defined RouterA#show ip ospf interface s0/0 Serial0 is up, line protocol is up Internet Address 192.1.1.1/24, Area Process ID 64, Router ID 1.1.1.1, Network Type POINT_TO_MULTIPOINT, Cost: 64 Transmit Delay is sec, State POINT_TO_MULTIPOINT, Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit Hello due in 00:00:01 Neighbor Count is 1, Adjacent neighbor count is Adjacent with neighbor 2.2.2.2 Display the neighbor state on RouterA with the command show ip ospf neighbor Notice that RouterA is fully adjacent with RouterB (2.2.2.2), but there is no concept of DR; the link is treated as a point−to−point link; however, the difference is that all routers can be on the same subnet RouterA#show ip ospf neighbor Neighbor ID Pri State 2.2.2.2 FULL/ − Dead Time 00:01:59 Address 192.1.1.2 Lab #40: Configure OSPF Interface Parameters Equipment Needed The following equipment is needed to perform this lab exercise: • Three Cisco routers, each having one serial port and one Ethernet port • Cisco IOS 10.0 or higher • A PC running a terminal emulation program • Two Cisco V.35 DCE/DTE crossover cables • One Ethernet hub and two Ethernet cables • Cisco rolled cable for console port access 326 Interface Serial0/0 Overview The Cisco IOS allows the administrator to alter certain interface−specific OSPF parameters This lab will deal with three of the more commonly used ones (cost, hello interval, and dead interval) The cost parameter sets the cost of OSPF sending a packet over particular interface By default, the cost is calculated using the formula (100,000,000/bandwidth of the link) So by default, the cost of using an Ethernet interface is 100 million divided by 10 million, which equals 10 The OSPF cost parameter is very useful in manipulating the flow of traffic, especially if you wish to prefer a slower link to a faster link The OSPF hello interval is the length of time in seconds between sending hello packets on a particular interface The hello interval must be consistent across all routers in an attached network The hello interval will vary based on the interface network type (broadcast = 10, non−broadcast = 30, point−to−point = 10, and point−to−multipoint = 30) The OSPF dead interval is the length of time in seconds that a hello packet must not be seen from a neighboring router before the neighbor is declared down The dead interval must be consistent across all routers in an attached network According to the interface network type, the dead interval will vary (broadcast = 40, non−broadcast = 120, point−to−point = 40, and point−to−multipoint = 120) Configuration Overview This lab will demonstrate configuring OSPF interface specific parameters (cost, hello interval, and dead interval) The serial interface between RouterA and RouterB will be configured for a cost of 66, which is two higher than the default of the serial link connecting RouterB and RouterC The OSPF hello interval will be set to 20, and the dead interval will be set to 120 on the serial interface connecting RouterA and RouterB RouterA and RouterC will attach to RouterB via a V.35 crossover cable RouterB will act as the DCE supplying clock RouterA and RouterC will also be attached via an Ethenet hub; all IP addresses are as per Figure 8−14 Figure 8−14: Configure OSPF interface parameters Router Configurations The configurations for the routers in this example are as follows (key OSPF commands are highlighted in bold) RouterA ! version 11.2 no service udp−small−servers no service tcp−small−servers 327 ! hostname RouterA ! interface Loopback0 ← Defines a virtual interface the IP address is used as the router ID ip address 1.1.1.1 255.255.255.0 ! interface Ethernet0/0 ip address 10.1.1.2 255.255.255.0 ! interface Serial0/0 ip address 192.1.1.1 255.255.255.0 ip ospf cost 66 ip ospf hello−interval 20 ip ospf dead−interval 120 ! interface Serial1/0 no ip address shutdown ! ! router ospf 64 ← Enables OSPF process 64 on the router network 192.1.1.0 0.0.0.255 area ← Specifies what interface OSPF will be run on and what area the interface will be in network 1.1.1.1 0.0.0.0 area network 10.1.1.0 0.0.0.0.255 area ! no ip classless ! line line aux line vty login ! end RouterB version 11.2 no service udp−small−servers no service tcp−small−servers ! hostname RouterB ! ! interface Loopback0 ← Defines a virtual interface the IP address is used as the router ID ip address 2.2.2.2 255.255.255.0 ! interface Ethernet0/0 no ip address shutdown ! interface Serial0/0 ip address 192.1.1.2 255.255.255.0 ip ospf cost 66 ip ospf hello−interval 20 ip ospf dead−interval 120 clockrate 500000 ! interface Serial0/1 ip address 193.1.1.2 255.255.255.0 clockrate 500000 ! 328 ... "igrp 64" Sending updates every 90 seconds, next due in 31 seconds Invalid after 270 seconds, hold down 280, flushed after 630 Outgoing update filter list for all interfaces is not set Incoming... as a subinterface type point−to−point A subinterface is a logical way of defining an interface The same physical interface can be split into multiple logical interfaces; this was originally created... the backbone, a virtual link must be configured Virtual links will be discussed later in the chapter All areas inject routing information into the backbone area (area 0), and the backbone propagates