Cis82 discard route

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Cis82 discard route

  1. 1. Discard Routes andAvoiding Routing Loops Rick Graziani Cabrillo College
  2. 2. Scenario ISP Network ISP ISP has static routes for 172.16.0.0/16 and RTA has a static default 192.168.1.0/24 to RTA route 0.0.0.0/0 to ISP Central Office Remote Office 172.16.1.0/24 RTA 172.16.4.0/24 172.16.2.0/24 172.16.3.0/24 172.16.5.0/24 192.168.1.0/24 RTB RTC Customer Network 172.16.0.0/16 and 192.168.1.0/24Rick Graziani graziani@cabrillo.edu 2
  3. 3. Situation Normal RouterA#show ip route 172.16.0.0/24 is subnetted, 3 subnets C 172.16.1.0 is directly connected, Ethernet0 C 172.16.2.0 is directly connected, Ethernet1 R 172.16.3.0 [120/1] via 172.16.2.1, 00:00:20, Ethernet1 R 172.16.4.0 [120/2] via 172.16.2.1, 00:00:20, Ethernet1 S* 0.0.0.0/0 is directly connected, Serial1Rick Graziani graziani@cabrillo.edu 3
  4. 4. Link Down XRick Graziani graziani@cabrillo.edu 4
  5. 5. Link Down X RouterA#show ip route 172.16.0.0/24 is subnetted, 3 subnets C 172.16.1.0 is directly connected, Ethernet0 C 172.16.2.0 is directly connected, Ethernet1 S* 0.0.0.0/0 is directly connected, Serial1Rick Graziani graziani@cabrillo.edu 5
  6. 6. Link down – Solution#1: no ip classless XRouterA#show ip route 172.16.0.0/24 is subnetted, 3 subnetsC 172.16.1.0 is directly connected, Ethernet0C 172.16.2.0 is directly connected, Ethernet1S* 0.0.0.0/0 is directly connected, Serial1Rick Graziani graziani@cabrillo.edu 6
  7. 7. Link down – Solution#2: Discard Route XRTA(config)# ip route 172.16.0.0 255.255.0.0 null0Rick Graziani graziani@cabrillo.edu 7
  8. 8. Link down – Solution#2: Discard Route XRTA(config)# ip route 172.16.0.0 255.255.0.0 null0 RouterA#show ip route 172.16.0.0/16 is subnetted, 3 subnets, 2 masks S 172.16.0.0/16 is directly connected, Null0 C 172.16.1.0/24 is directly connected, Ethernet0 C 172.16.2.0/24 is directly connected, Ethernet1 S* 0.0.0.0/0 is directly connected, Serial1Rick Graziani graziani@cabrillo.edu 8
  9. 9. Link down – Solution #2: Discard Route RouterA#show ip route 172.16.0.0/16 is subnetted, 3 subnets, 2 masks S 172.16.0.0/16 is directly connected, Null0 C 172.16.1.0/24 is directly connected, Ethernet0 C 172.16.2.0/24 is directly connected, Ethernet1 S* 0.0.0.0/0 is directly connected, Serial1• When all links are up… RouterA#show ip route 172.16.0.0/16 is subnetted, 5 subnets, 2 masks S 172.16.0.0/16 is directly connected, Null0 C 172.16.1.0/24 is directly connected, Ethernet0 C 172.16.2.0/24 is directly connected, Ethernet1 R 172.16.3.0/24 [120/1] via 172.16.2.1, 00:00:20, Ethernet1 R 172.16.4.0/24 [120/2] via 172.16.2.1, 00:00:20, Ethernet1 S* 0.0.0.0/0 is directly connected, Serial1 Rick Graziani graziani@cabrillo.edu 9
  10. 10. Discard Routes andAvoiding Routing Loops Rick Graziani Cabrillo College

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