redistribution_frenzy

I have to say that going from Distribute-Lists where you are just applying standard ACL’s to Redistribution is like little league softball compared to Route-Map configuration for them. I planned to study them more before throwing a post up with some lab work getting done, but this is a really exciting topic to me, as it definitely shows such a high level of complexity.

Once I went through the ‘lingo’ a couple times, and really took a moment to understand what was happening, its essentially a mechanism (as I am learning it now) to allow you to stack route changes onto redistributed routes my network number in a LOT of different ways.

As I said I am only just beginning these, so I will just perform a simple one to demonstrate the concepts and commands, as well as starting off with some NEED TO KNOW facts for exam day:

  • Route-Maps are used for MUCH more than Redistribution – That just happens to be what I am using them for at this point in studies
  • “sh route-map” is your one stop shop for all the info you need for route-maps on the router you are troubleshooting or configuring
  • You must write separate ACL’s for each route-map sequence of clauses (except for the last “catch all” clause described below
  • When writing ACL’s for route maps, permit on the ACL, and deny on the route-map configuration
  • Route-map names are what is used in the redistribution configuration, the numbers at the end are “sequence” type numbers, they seem arbitrary but best to keep them in order like an ACL, so it follows your ACL’s with it’s set of “clauses”
  • “Clauses” are configurations of the different route-map sequences, every setting configured on a route-map would be considered a “clause”
  • A catch-all “clause” at the end of the route-map configuration is an excellent idea, kind of like adding “permit ip any any” to an ACL to allow any traffic you haven’t explicitly denied in the ACL

So enough of the main points, as they basically covered what a route map does, however from the bit I’ve learned I am going to attempt a simple configuration for tonight. I will look at R4 from the Myself Inc topology, and configure / apply a set of ACL’s and a route-map to reconfigure how the arrive to R4 from R3 our trusty ASBR.

So to start I want to make sure R3 and R4 are ready to rock:

R4#sh ip route

Gateway of last resort is not set

4.0.0.0/32 is subnetted, 1 subnets
C        4.4.4.4 is directly connected, Loopback4
172.12.0.0/16 is variably subnetted, 5 subnets, 2 masks
O        172.12.33.3/32 [110/2] via 172.12.34.3, 00:42:56, FastEthernet0/1
C        172.12.34.0/24 is directly connected, FastEthernet0/1
L        172.12.34.4/32 is directly connected, FastEthernet0/1
C        172.12.44.0/24 is directly connected, Loopback44
L        172.12.44.4/32 is directly connected, Loopback44

 

^ What is this now?

R4#show ip ospf nei

Neighbor ID     Pri   State           Dead Time   Address         Interface
172.12.33.3       0   FULL/  –           –        172.12.34.3     OSPF_VL0
172.12.33.3       1   FULL/BDR        00:00:37    172.12.34.3     FastEthernet0/1
R4#
ASR#3
[Resuming connection 3 to r3 … ]

R3#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R3(config)#router ospf 1
R3(config-router)#redist
R3(config-router)#redistribute rip subnets
R3(config-router)#
ASR#4
[Resuming connection 4 to r4 … ]

R4#sh ip route

Gateway of last resort is not set

4.0.0.0/32 is subnetted, 1 subnets
C        4.4.4.4 is directly connected, Loopback4
O E2  5.0.0.0/8 [110/20] via 172.12.34.3, 00:00:01, FastEthernet0/1
172.12.0.0/16 is variably subnetted, 7 subnets, 2 masks
O E2     172.12.15.0/24 [110/20] via 172.12.34.3, 00:00:01, FastEthernet0/1
O        172.12.33.3/32 [110/2] via 172.12.34.3, 00:43:50, FastEthernet0/1
C        172.12.34.0/24 is directly connected, FastEthernet0/1
L        172.12.34.4/32 is directly connected, FastEthernet0/1
C        172.12.44.0/24 is directly connected, Loopback44
L        172.12.44.4/32 is directly connected, Loopback44
O E2     172.12.123.0/24 [110/20] via 172.12.34.3, 00:00:01, FastEthernet0/1
R4#

Much better, now we have 3 E2 routes to mess with.

I noticed there is one last video about 2 way redistribution and route-maps which is what I am attempting to do here, however I am way too spent and exhausted from being sick to fully get into it, however the game board is set so next post will be heavy labbing with lots of router output segments that I know every reading (me) loves 🙂