Tài liệu học CCNA kỳ 3 Module1

1 Module 1 – Introduction to Classless Routing CCNA 3 version 3.1 Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 2 Overview • Define VLSM and briefly describe the reasons for its use • Divide a major network into subnets of different sizes using VLSM • Define route aggregation and summarization as they relate to VLSM • Configure a router using VLSM • Identify the key features of RIP v1 and RIP v2 • Identify the important differences between RIP v1 and RIP v2 • Configure RIP v2 • Verify and troubleshoot RIP v2 operation • Configure default routes using the ip route and ip default- network commands 2 Advanced IP Management Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 4 IPv4 Address Classes • No medium size host networks • In the early days of the Internet, IP addresses were allocated to organizations based on request rather than actual need. 3 Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 5 IPv4 Address Classes Class D Addresses • A Class D address begins with binary 1110 in the first octet. • First octet range 224 to 239. • Class D address can be used to represent a group of hosts called a host group, or multicast group. Class E Addresses First octet of an IP address begins with 1111 • Class E addresses are reserved for experimental purposes and should not be used for addressing hosts or multicast groups. Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 6 IP addressing crisis • Address Depletion • Internet Routing Table Explosion 4 Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 7 IPv4 Addressing Subnet Mask • One solution to the IP address shortage was thought to be the subnet mask. • Formalized in 1985 (RFC 950), the subnet mask breaks a single class A, B or C network in to smaller pieces. Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 8 Using /24 subnet 190.52.1.2 190.52.2.2 190.52.3.2 Network Network Subnet Host But internal routers think all these addresses are on different networks, called subnetworks Externet routers still “see” this net as 190.52.0.0 Class B Network Network Host Host Given the Class B address 190.52.0.0 Subnet Example 5 Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 9 Using the 3rd octet, 190.52.0.0 was divided into: 190.52.1.0 190.52.2.0 190.52.3.0 190.52.4.0 190.52.5.0 190.52.6.0 190.52.7.0 190.52.8.0 190.52.9.0 190.52.10.0 190.52.11.0 190.52.12.0 190.52.13.0 190.52.14.0 190.52.15.0 190.52.16.0 190.52.17.0 190.52.18.0 190.52.19.0 and so on Network Network Subnet Host Subnet Example Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 10 All Zeros and All Ones Subnets Using the All Ones Subnet • There is no command to enable or disable the use of the all-ones subnet, it is enabled by default. Router(config)#ip subnet-zero • The use of the all-ones subnet has always been explicitly allowed and the use of subnet zero is explicitly allowed since Cisco IOS version 12.0. RFC 1878 states, "This practice (of excluding all-zeros and all-ones subnets) is obsolete! Modern software will be able to utilize all definable networks." Today, the use of subnet zero and the all-ones subnet is generally accepted and most vendors support their use, though, on certain networks, particularly the ones using legacy software, the use of subnet zero and the all-ones subnet can lead to problems. CCO: Subnet Zero and the All-Ones Subnet http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a 0080093f18.shtml 6 Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 11 Long Term Solution: IPv6 (coming) • IP v6, or IPng (IP – the Next Generation) uses a 128-bit address space, yielding 340,282,366,920,938,463,463,374,607,431,768,211,456 possible addresses. 3,4 e38 • IPv6 has been slow to arrive • IPv4 revitalized by new features, making IPv6 a luxury, and not a desperately needed fix • IPv6 requires new software; IT staffs must be retrained • IPv6 will most likely coexist with IPv4 for years to come. • Some experts believe IPv4 will remain for more than 10 years. Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 12 Short Term Solutions: IPv4 Enhancements • CIDR (Classless Inter-Domain Routing) – RFCs 1517, 1518, 1519, 1520 • VLSM (Variable Length Subnet Mask) – RFC 1009 • Private Addressing - RFC 1918 • NAT/PAT (Network Address Translation / Port Address Translation) – RFC 7 Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 13 • By 1992, members of the IETF were having serious concerns about the exponential growth of the Internet and the scalability of Internet routing tables. • The IETF was also concerned with the eventual exhaustion of 32-bit IPv4 address space. • IETF’s response was the concept of Supernetting or CIDR, “cider”. • To CIDR-compliant routers, address class is meaningless. – The network portion of the address is determined by the network subnet mask, network-prefix or prefix-length (/8, /19, etc.) – The network address is NOT determined by the first octet (first two bits), 200.10.0.0/16 or 15.10.160.0/19 • CIDR helped reduced the Internet routing table explosion with supernetting and reallocation of IPv4 address space. CIDR (Classless Inter-Domain Routing) Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 14 Without CIDR, a router must maintain individual routing table entries for these class B networks. With CIDR, a router can summarize these routes into eight networks by using a 13-bit prefix: 172.24.0.0 /13 1. Count the number of left-most matching bits, /13 2. Add all zeros after the last matching bit: 172.24.0.0 = 10101100 00011000 00000000 00000000 Steps: 8 Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 15 CIDR (Classless Inter-Domain Routing) • By using a prefix address to summarizes routes, administrators can keep routing table entries manageable, which means the following – More efficient routing – A reduced number of CPU cycles when recalculating a routing table, or when sorting through the routing table entries to find a match – Reduced router memory requirements • Route summarization is also known as: – Route aggregation – Supernetting • Supernetting is essentially the inverse of subnetting. Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 16 • Company XYZ needs to address 400 hosts. • Its ISP gives them two contiguous Class C addresses: – 207.21.54.0/24 – 207.21.55.0/24 • Company XYZ can use a prefix of 207.21.54.0 /23 to supernet these two contiguous networks. (Yielding 510 hosts) • 207.21.54.0 /23 – 207.21.54.0/24 – 207.21.55.0/24 23 bits in common Supernetting Example 9 Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 17 • With the ISP acting as the addressing authority for a CIDR block of addresses, the ISP’s customer networks, which include XYZ, can be advertised among Internet routers as a single supernet. Supernetting Example Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 18 CIDR and the Provider 10 Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 19 200.199.48.0/24 11001000 11000111 001100 00 00000000 200.199.49.0/24 11001000 11000111 001100 01 00000000 200.199.50.0/24 11001000 11000111 001100 10 00000000 200.199.51.0/24 11001000 11000111 001100 11 00000000 200.199.48.0/22 11001000 11000111 001100 00 00000000 200.199.52.0/24 11001000 11000111 001101 00 00000000 200.199.53.0/24 11001000 11000111 001101 01 00000000 200.199.54.0/24 11001000 11000111 001101 10 00000000 200.199.55.0/24 11001000 11000111 001101 11 00000000 200.199.52.0/22 11001000 11000111 001101 00 00000000 200.199.56.0/24 11001000 11000111 00111 000 00000000 200.199.57.0/24 11001000 11000111 00111 001 00000000 ………… 200.199.63.0/24 11001000 11000111 00111 111 00000000 200.199.56.0/21 11001000 11000111 00111 000 00000000 CIDR and the provider Họcviệnmạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 20 • Dynamic routing protocols must send network address and mask (prefix-length) information in their routing updates. • In other words, CIDR requires classless routing protocols for dynamic routing. CIDR Restrictions [...]... protocol debugging is on ISP#01: 23: 34: RIP: received v2 update from 192.168.4.22 on Serial1 01: 23: 34: 172 .30 .100.0/24 -> 0.0.0.0 in 1 hops 01: 23: 34: 172 .30 .110.0/24 -> 0.0.0.0 in 1 hops Includes mask ISP# 01: 23: 38: RIP: received v2 update from 192.168.4.26 on Serial0 01: 23: 38: 172 .30 .2.0/24 -> 0.0.0.0 in 1 hops 01: 23: 38: 172 .30 .1.0/24 -> 0.0.0.0 in 1 hops multicast ISP# 01:24 :31 : RIP: sending v2 update to... destined for 172 .30 .0.0/16 207.0.0.0/16 207.1.0.0/16 207.2.0.0/16 207 .3. 0.0/16 etc Internet 25 s0 s1 21 192.168.4.24 /30 192.168.4.20 /30 172 .30 .200 .32 /28 Lo2 26 172 .30 .2.0/24 s0 Lo0 1 SantaCruz1 1 e0 172 .30 .1.0/24 s0 22 Lo1 SantaCruz2 1 e0 ` Lo0 1 172 .30 .200.16/28 172 .30 .110.0/24 172 .30 .100.0/24 Học viện mạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 28 SantaCruz1 router rip network 172 .30 .0.0 network... 224.0.0.9 via Ethernet0 (10.0.0.1) 01:24 :31 : 172 .30 .2.0/24 -> 0.0.0.0, metric 2, tag 0 01:24 :31 : 172 .30 .1.0/24 -> 0.0.0.0, metric 2, tag 0 01:24 :31 : 172 .30 .100.0/24 -> 0.0.0.0, metric 2, tag 0 01:24 :31 : 172 .30 .110.0/24 -> 0.0.0.0, metric 2, tag 0 01:24 :31 : 192.168.4.24 /30 -> 0.0.0.0, metric 1, tag 0 01:24 :31 : 192.168.4.20 /30 -> 0.0.0.0, metric 1, tag 0 Học viện mạng Cisco Bách Khoa - Website:... 11 01 10 11 Học viện mạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 29 2 Hosts 1 93 & 194 197 & 198 201 & 202 205 & 206 209 & 210 2 13 & 214 217 & 218 221 & 222 30 15 207.21.24.192 /30 207.21.24.204 /30 207.21.24.216 /30 207.21.24.128/27 207.21.24.96/27 207.21.24.64/27 207.21.24.208 /30 207.21.24.200 /30 207.21.24.196 /30 207.21.24.160/27 • • 207.21.24.224/27 207.21.24 .32 /27 207.21.24.212 /30 207.21.24.0/27... subnets with 2 hosts each /30 subnets are very useful for serial networks Học viện mạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 207.21.24.192/27 0 1 2 3 4 5 6 7 207.21.24.192 /30 207.21.24.196 /30 207.21.24.200 /30 207.21.24.204 /30 207.21.24.208 /30 207.21.24.212 /30 207.21.24.216 /30 207.21.24.220 /30 207.21.24 11000000 /30 207.21.24 110 00000 207.21.24 110 00100 207.21.24 110 01000 207.21.24 110... 207.0.0.0/8 1 207.0.0.0/16 207.1.0.0/16 207.2.0.0/16 207 .3. 0.0/16 etc .1 e0 ISP 25 Supernet, classless routing protcols will route supernets (CIDR) s0 s1 21 192.168.4.24 /30 192.168.4.20 /30 172 .30 .200 .32 /28 Lo2 26 172 .30 .2.0/24 s0 Lo0 1 SantaCruz1 1 e0 s0 22 Lo1 ` 172 .30 .200.16/28 SantaCruz2 Lo0 1 e0 1 172 .30 .110.0/24 172 .30 .100.0/24 172 .30 .1.0/24 Học viện mạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com... network 172 .30 .0.0 network 192.168.4.0 version 2 no auto-summary 207.0.0.0/16 207.1.0.0/16 207.2.0.0/16 207 .3. 0.0/16 etc Internet 1 e0 ISP 25 s0 s1 21 192.168.4.24 /30 192.168.4.20 /30 172 .30 .200 .32 /28 ISP router rip redistribute static network 10.0.0.0 network 192.168.4.0 version 2 no auto-summary Lo2 26 172 .30 .2.0/24 s0 s0 Lo0 1 SantaCruz1 22 1 e0 1 e0 172 .30 .200.16/28 ` Lo1 SantaCruz2 Lo0 1 172 .30 .110.0/24... 172 .30 .110.0/24 172 .30 .100.0/24 172 .30 .1.0/24 Other way: on S0 or S1 of ISP: ip summary-address rip …… ip route 207.0.0.0 255.0.0.0 null0 Học viện mạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com SantaCruz2#show ip route C C R R C C R C R R Examining a Routing Table 172 .30 .0.0/16 is variably subnetted, 6 subnets, 2 masks 172 .30 .200 .32 /28 is directly connected, Loopback2 172 .30 .200.16/28 is directly... 207.2.0.0/16 207 .3. 0.0/16 etc Internet router rip static route to 207.0.0.0/8 10.0.0.0/8 redistribute static network 10.0.0.0 1 1 e0 ISP network 192.168.4.0 25 s0 s1 21 version 2 no auto-summary 192.168.4.24 /30 192.168.4.20 /30 default-information originate 172 .30 .200 .32 /28 Lo2 ip route 207.0.0.0 255.0.0.0 null0 ip route 0.0.0.0 0.0.0.0 10.0.0.2 etherenet0 26 172 .30 .2.0/24 s0 Lo0 1 SantaCruz1 1 e0 172 .30 .1.0/24... etherenet0 26 172 .30 .2.0/24 s0 Lo0 1 SantaCruz1 1 e0 172 .30 .1.0/24 s0 22 Lo1 SantaCruz2 1 e0 ` Lo0 1 172 .30 .200.16/28 172 .30 .110.0/24 172 .30 .100.0/24 Học viện mạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 30 RIPv2 Summary Học viện mạng Cisco Bách Khoa - Website: www.ciscobachkhoa.com 61 31