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Tag your Routes Before Redistribution

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Tag your Routes Before Redistribution

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Tag your Routes Before Redistribution

  1. 1. Tag Your Routes Before Redistribution Presented by Md. Abdullah Al Naser Sr. Systems Specialist MetroNet Bangladesh Limited Founder, mn-LAB
  2. 2. Presented by – Md. Abdullah Al Naser Page # 2 Before Starting….. ● Experts say that, don’t REDISTRIBUTE IGP routes to the upstreams while you configure BGP – That’s True. ● But many engineers still prefer this REDISTRIBUTION for their internal networks and also for their clients’ internal networks in complex routing scenario – Design Requirements.
  3. 3. Presented by – Md. Abdullah Al Naser Page # 3 What is Redistribution? ● It’s possible that we have multiple routing protocols in our network and we’ll need some method to exchange routing information between the different protocols. This method is called redistribution. ● Redistribution between routing protocols (RIP, OSPF, EIGRP, BGP). ● Static routes can be redistributed into a routing protocol. ● Directly connected routes can also be redistributed into a routing protocol.
  4. 4. Presented by – Md. Abdullah Al Naser Page # 4 What is Redistribution? ● Redistribution is not done automatically. ● Redistribution happens outbound. ● When we redistribute from one routing protocol into another we have to use a seed metric. OSPF: Cost EIGRP: K-Values (bandwidth, delay, load and reliability) RIP: Hop count
  5. 5. Presented by – Md. Abdullah Al Naser Page # 5 Configuring Redistribution – Just an example R1(config)#router ospf 1 R1(config-router)#network 1.1.1.0 0.0.0.255 area 0 R1(config-router)#network 192.168.12.0 0.0.0.255 area 0 R2(config)#router ospf 1 R2(config-router)#network 192.168.12.0 0.0.0.255 area 0 R2(config)#router rip R2(config-router)#version 2 R2(config-router)#no auto-summary R2(config-router)#network 192.168.23.0 R3(config)#router rip R3(config-router)#version 2 R3(config-router)#network 3.3.3.0 R3(config-router)#network 192.168.23.0
  6. 6. Presented by – Md. Abdullah Al Naser Page # 6 Configuring Redistribution – Just an example R2(config)#router rip R2(config-router)#redistribute ospf 1 metric 5 R2(config)#router ospf 1 R2(config-router)#redistribute rip subnets R3#show ip route rip R 192.168.12.0/24 [120/5] via 192.168.23.2, 00:00:00, FastEthernet0/0 R 1.1.1.1 [120/5] via 192.168.23.2, 00:00:00, FastEthernet0/0 R1#show ip route ospf O E2 3.3.3.0 [110/20] via 192.168.12.2, 00:00:21, FastEthernet0/0 O E2 192.168.23.0/24 [110/20] via 192.168.12.2, 00:00:21, FastEthernet0/0
  7. 7. Presented by – Md. Abdullah Al Naser Page # 7 Multipoint Redistribution ● So far so good. ● But the problem will arise during multipoint redistribution. ● It can mislead you to a sub optimal routing and a routing loop.
  8. 8. Presented by – Md. Abdullah Al Naser Page # 8 Multipoint Redistribution Let’s go into the deep R2#show ip route rip R 1.1.1.0 [120/6] via 192.168.12.1, 00:00:09, FastEthernet1/0
  9. 9. Presented by – Md. Abdullah Al Naser Page # 9 Multipoint Redistribution Let’s redistribute RIP routes into OSPF R3 & R4# (config)#router ospf 1 (config-router)#redistribute rip subnets
  10. 10. Presented by – Md. Abdullah Al Naser Page # 10 Multipoint Redistribution Let’s check R4’s routing table R4#show ip route ospf O E2 1.1.1.0 [110/20] via 192.168.34.3, 00:01:14, FastEthernet0/1
  11. 11. Presented by – Md. Abdullah Al Naser Page # 11 Sub Optimal Routing Sub optimal routing refers to inefficient routing – not good
  12. 12. Presented by – Md. Abdullah Al Naser Page # 12 Multipoint Redistribution (cont..) Let’s redistribute OSPF routes into RIP R3 & R4# (config)#router rip (config-router)#redistribute ospf 1 metric 1
  13. 13. Let’s check R2’s routing table again R2#show ip route rip R 1.1.1.0 [120/1] via 192.168.24.4, 00:00:05, FastEthernet0/1 R2#traceroute 1.1.1.1 1 192.168.24.4 1388 msec 620 msec 744 msec 2 192.168.34.3 2552 msec 2308 msec 1904 msec 3 192.168.23.2 56 msec 48 msec 48 msec 4 192.168.24.4 76 msec 76 msec 72 msec 5 192.168.34.3 112 msec 124 msec 100 msec 6 192.168.23.2 96 msec 100 msec 92 msec 7 192.168.24.4 124 msec 140 msec 124 msec 8 192.168.34.3 156 msec 168 msec 176 msec 9 192.168.23.2 152 msec 136 msec 156 msec 10 192.168.24.4 176 msec 184 msec 172 msec Presented by – Md. Abdullah Al Naser Page # 13 Routing Loop
  14. 14. Let’s check R2’s routing table again R2#show ip route rip R 1.1.1.0 [120/1] via 192.168.24.4, 00:00:05, FastEthernet0/1 Presented by – Md. Abdullah Al Naser Page # 14 Routing Loop
  15. 15. Be careful You should never redistribute routes like this: Routing Protocol X ----> Y ----> X Presented by – Md. Abdullah Al Naser Page # 15 Important Redistribution Rules
  16. 16. ● Redistribution Filtering – not scalable ● Route Filtering – not scalable at all ● Route Tagging – the best solution Presented by – Md. Abdullah Al Naser Page # 16 Looking for Solution
  17. 17. R3 & R4# (config)#route-map TAGGING deny 10 (config-route-map)#match tag 1234 (config-route-map)#exit (config)#route-map TAGGING permit 20 (config-route-map)#set tag 1234 (config)#router rip (config-router)#redistribute ospf 1 metric 1 route-map TAGGING (config-router)#exit (config)#router ospf 1 (config-router)#redistribute rip subnets route-map TAGGING Presented by – Md. Abdullah Al Naser Page # 17 Configuring Route Tagging
  18. 18. Let’s check R2’s routing table again R2#show ip route rip R 1.1.1.0 [120/6] via 192.168.12.1, 00:00:01, FastEthernet1/0 It looks good now….. But sub optimal routing is still there…. Presented by – Md. Abdullah Al Naser Page # 18 Routing Loop is now Removed
  19. 19. Be careful again Always prefer your “internal” routes over “external” routes. Whenever your internal route has a higher AD than the external route, you have to be careful! Presented by – Md. Abdullah Al Naser Page # 19 Another Important Redistribution Rules
  20. 20. ● Decrease the AD of the internal route(s) or ● Increase the AD of the external route(s) Presented by – Md. Abdullah Al Naser Page # 20 Possible Solution
  21. 21. Thank you very much

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