Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Introduction to Routing doc

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Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Introduction to Routing doc

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Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Introduction to Routing and Packet Forwarding g Routing Protocols and Concepts – Chapter ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Objectives Identify a router as a co pu e with a OS a d de y ou e computer an and hardware designed for the routing process Demonstrate the ability to configure devices and apply addresses Describe the structure of a routing table table Describe how a router determines a path and switches packets ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Router as a Computer Describe the bas c purpose o a router esc be e basic pu pose of ou e -Computers that specialize in sending packets over the data network They are responsible for interconnecting networks by selecting the best path for a packet to travel and forwarding packets to their destination Routers have many of the same hardware and software components that are found in other computers p p including: –CPU –RAM –ROM –Operating System ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Router as a Computer Router components and their functions” p CPU - Executes operating system instructions such as system initialization, routing functions, and switching functions Random access memory (RAM) -RAM stores the instructions and data needed to be executed by the CPU RAM is used to store these components: –Operating System: The Cisco IOS (Internetwork Operating System) is copied g p into RAM during bootup –Running Configuration File: This is the configuration file that stores the configuration commands that the router IOS is currently using –IP Routing Table: This file stores information about directly connected and g y remote networks It is used to determine the best path to forward the packet –ARP Cache: This cache contains the IPv4 address to MAC address mappings, similar to the ARP cache on a PC The ARP cache is used on routers that h h have LAN i interfaces such as E h f h Ethernet i interfaces f –Packet Buffer: Packets are temporarily stored in a buffer when received on an interface or before they exit an interface RAM is volatile memory and loses its content when the router is powered down or restarted ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Router as a Computer Router co po e s a d their functions” ou e components and e u c o s Read-only memory (ROM) - Holds diagnostic software used when router is powered up Stores the router’s bootstrap p g program –ROM is a form of permanent storage Cisco devices use ROM to store: –The bootstrap instructions –Basic diagnostic software –Scaled-down version of IOS ROM uses firmware, which is software that is embedded inside the integrated circuit – Firmware includes the software that does not normally need to be modified or upgraded, such as the bootup instructions – ROM does not lose its contents when the router loses power or is restarted ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public Router components and their functions” Non-volatile RAM (NVRAM) - Stores startup configuration This may include IP addresses (Routing protocol Hostname of router) protocol, NVRAM (Nonvolatile RAM) does not lose its information when power is turned off This is in contrast to the most common forms of RAM, such as DRAM, that requires continual power to maintain its information NVRAM is used by the Cisco IOS as permanent storage for the startup configuration file file All configuration changes are stored in the running-config file in RAM, and with few exceptions, are implemented immediately by the IOS To save those changes in case the router is restarted or loses power, the running-config must be copied to NVRAM where it is stored as the startup-config file NVRAM retains its NVRAM, file contents even when the router reloads or is powered off Flash memory - Contains the operating system (Cisco IOS) In most models of Cisco routers, the IOS is permanently stored in flash memory and copied into RAM during the bootup process, where it is then executed by the CPU Flash consists of SIMMs or PCMCIA cards, which can be upgraded to increase the amount of flash memory memory Interfaces - There exist multiple physical interfaces that are used to connect network Examples of interface types: -Ethernet / fast Ethernet interfaces -Serial interfaces -Management interfaces ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Router R t as a C Computer t Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Router as a Computer Router co po e s ou e components ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Internetwork Operating System The operating system software used in Cisco routers is known as Cisco Internetwork Operating System (IOS) (IOS) – Cisco IOS is a multitasking operating system that is integrated with routing, switching, internetworking, and telecommunications functions Although the Cisco IOS may appear to be the same on many routers, there are many different IOS images – An IOS image is a file that contains the entire IOS for that router Cisco creates many different types of IOS images, depending upon the model of the router and the features within the IOS – Typically the more features in the IOS, the larger the IOS image, and therefore, the more flash and RAM that is required to store and load the IOS Although some routers provide a graphical user interface (GUI), the command li i t f d line interface (CLI) i a much more common method of is h th d f configuring Cisco routers – The CLI is used throughout this curriculum Upon bootup the startup config file in NVRAM is copied into RAM and bootup, startup-config stored as the running-config file – IOS executes the configuration commands in the running-config Any changes entered by the network administrator are stored in the runningconfig and are immediately implemented by the IOS IOS ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Overview - Managing Cisco IOS Software (cont) ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Router as a Computer Major p ases to the ajo phases o e router boot-up process Test router hardware Power-On Self Test (POST) Execute bootstrap loader p Locate & load Cisco IOS software -Locate IOS Locate -Load IOS Locate & load startup configuration file or enter setup mode p program looks -Bootstrap p g for configuration file ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 10 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com OSPF in Multiaccess Networks OSPF Interface Priority Modify Priority –Router(config-if)#ip ospf priority {0 - 255} Force Election –After d i a shutdown and a no shutdown Aft doing h td d h td on the FastEthernet 0/0 interfaces of all three routers, we see the result of the change of OSPF interface priorities –The show ip ospf neighbor command on RouterC now shows that RouterA (Router ID 192.168.31.11) is the DR with the highest OSPF interface priority of 200 p y –RouterB (Router ID 192.168.31.22) is still the BDR with the next highest OSPF interface priority of 100 –Notice f N ti from R t A' output of show ip RouterA's t t f h i ospf neighbor that it does not show a DR, because RouterA is the actual DR on this network ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved DR BDR Cisco Public 57 Redistributing Redistrib ting an OSPF Defa lt Ro te Default Route Topology includes a link to ISP –Router connected to ISP R t t dt In this topology, the Called an autonomous system border router Loopback1 (Lo1) simulate the connection to another Used to propagate a default route router –Example of static default route R1(config)#ip route 0.0.0.0 0.0.0.0 loopback –Requires the use of the default-information originate command –Example of default-information originate command R1(config-router)#default-information originate ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 58 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com More OSPF Configuration The default route in R2 and R3 with the routing source OSPF, but with the additional code, E2 For R2, the route is: O*E2 0.0.0.0/0 [110/1] via 192.168.10.10, 00:05:34, Serial0/0/1 E2 denotes that this route is an OSPF External Type route the cost of an E2 route is always the external cost, irrespective of the interior cost to reach that route (CCNP) ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 59 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Redistributing an OSPF Default Route Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com More OSPF Configuration Fine-Tuning OSPF Since link speeds are getting faster it may be necessary to change reference bandwidth f values –Do this using the auto cost Do auto-cost reference-bandwidth command –Example: R1(config-router)#auto-cost reference-bandwidth 10000 •the default value is equivalent to 100 To increase it to 10GigE speeds, y would need g p , you to change the reference bandwidth to 10000 •Again, make sure you configure this command on all routers in the OSPF routing domain ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 60 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com More OSPF Configuration Fine-Tuning OSPF R1(config-router)#autocost reference-bandwidth 10000 •the default value is equivalent to 100 To increase it to 10GigE speeds you would need speeds, to change the reference bandwidth to 10000 R1 Before, the cost to 10.10.10.0/24 is 1172 After Aft configuring a new reference b d idth fi i f bandwidth, the cost for the same route is now 117287 ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 61 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com More OSPF Configuration Fine-Tuning OSPF Modifying OSPF timers –Reason to modify timers Faster detection of network failures –Manually modifying Hello & Dead intervals Router(config-if)#ip ospf hello-interval seconds Router(config-if)#ip ospf dead-interval seconds R t ( fi if)#i fd di t l d –Point to be made Hello & Dead intervals must be the same between neighbors ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 62 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com The End Questions? What will be the result of the DR and BDR elections for this single area OSPF network? (Choose three.) * Decision process: HQ will be DR for 10.4.0.0/16 ill b f 10 0/16 Router A will be DR for 10.4.0.0/16 HQ will be BDR for 10.4.0.0/16 10 0/16 Router A will be DR for 10.5.0.0/16 Remote will be DR for 10.5.0.0/16 10 0/16 Remote will be BDR for 10.5.0.0/16 ITE PC v4.0 Chapter Which segment will have election? Priority? Router ID (each router will only has ID)? Set using “router-ID” command Highest Loopback IP address? Highest physical IP address (include serial interface)? © 2007 Cisco Systems, Inc All rights reserved Cisco Public 63 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com The End Questions? The routers in the diagram are configured as shown The loopback interface on shown router R1 is labeled as lo0 All OSPF priorities are set to the default except for Ethernet0 of router R2, which has an OSPF priority of What will be the result of the OSPF DR/BDR elections on the 192.1.1.0 network? (Choose two.) R1 will be the DR R1 will be the BDR R2 will be the DR * Decision process: 1 Which segment will have election? Priority? Router ID (each router will only has ID)? R2 will be the BDR Set using “router-ID” command R3 will be the DR Highest Loopback IP address? R3 will be the BDR ITE PC v4.0 Chapter 1 Highest physical IP address (include serial interface)? © 2007 Cisco Systems, Inc All rights reserved Cisco Public 64 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Questions? * Decision process: 1 Which segment will have election? Priority? Router ID (each router will only has ID)? Highest Loopback IP address? ITE PC v4.0 Chapter Set using “router-ID” command Highest physical IP address (include serial interface)? © 2007 Cisco Systems, Inc All rights reserved Cisco Public 65 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Questions? Answer????? * Decision process: Which segment will have election? 2 Priority? i i ? Router ID (each router will only has ID)? Highest Loopback IP address? ITE PC v4.0 Chapter Set using “router-ID” command router ID Highest physical IP address (include serial interface)? i li f )? © 2007 Cisco Systems, Inc All rights reserved Cisco Public 66 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Questions? Answer????? HQ will be DR for 10.4.0.0/16 Router A will be DR for 10.4.0.0/16 HQ will b BDR f ill be for 10.4.0.0/16 * Decision process: Router A will be DR for 10.5.0.0/16 1 Which segment will have election? Priority? Remote will be DR for 10.5.0.0/16 Router ID (each router will only has ID)? Remote will be BDR for 10.5.0.0/16 10 0/16 ITE PC v4.0 Chapter 1 Set using “router-ID” command Highest Loopback IP address? Highest physical IP address (include serial interface)? © 2007 Cisco Systems, Inc All rights reserved Cisco Public 67 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Summary RFC 2328 describes OSPF link state concepts and operations OSPF Characteristics –A commonly deployed link state routing protocol –Employs DRs & BDRs on multi-access networks DRs & BDRs are elected DR & BDRs are used to transmit and receive LSAs –Uses packet types: Uses 1: HELLO 2: DATABASE DESCRIPTION 3: LINK STATE REQUEST 4: LINK STATE UPDATE 5: LINK STATE ACKNOWLEDGEMENT ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 68 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Summary OSPF Characteristics –Metric = cost Lowest cost = best path Configuration –Enable OSPF on a router using the following command E bl t i th f ll i d R1(config)#router ospf process-id –use the network command to define which interfaces will use participate in a given OSPF process R1(config-router)#network network-address wildcard-mask area area-id ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 69 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Summary Verifying OSPF configuration –Use the following commands show ip protocol show ip route show i ospf i t f h ip f interface show ip ospf neighbor ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 70 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ITE PC v4.0 Chapter © 2007 Cisco Systems, Inc All rights reserved Cisco Public 71 ... Public 25 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Stages of the router power-on boot sequence Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com. .. Cisco Public Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Router R t as a C Computer t Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Router... Public 14 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Router as a Computer show version Verify the router boot-up process: -The show version command is used to view

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