CCNP ROUTE Redistribution Lab: EIGRP And Distribute-Lists

In this lab from my CCNP ROUTE tutorial section, we’ll use distribute lists to filter EIGRP routes during redistribution.   Here’s the topology for this lab, with R1 running both EIGRP and RIPv2.

EIGRP Route Redistribution Lab Topology

R1 sees both of R2’s loopbacks via RIP.

R1#show ip route rip

R    2.0.0.0/8 [120/1] via 172.12.123.2, 00:00:16, Serial1/0

R    22.0.0.0/8 [120/1] via 172.12.123.2, 00:00:10, Serial1/0

Before we redistribute the connected and RIP subnets on R1 into EIGRP AS 100, I’ll use default-metric to set our default seed metric for EIGRP.  That way, I don’t have to list default metrics in the EIGRP redistribute statement (not that there’s anything wrong with that).

I’ll use IOS Help to remind you (and me!) of this command’s requirements:

R1(config)#router eigrp 100

R1(config-router)#default-metric ?

  <1-4294967295>  Bandwidth in Kbits per second


R1(config-router)#default-metric 1544 ?

  <0-4294967295>  Delay metric, in 10 microsecond units


R1(config-router)#default-metric 1544 ?

  <0-4294967295>  Delay metric, in 10 microsecond units


R1(config-router)#default-metric 1544 10 ?

  <0-255>  Reliability metric where 255 is 100% reliable


R1(config-router)#default-metric 1544 10 255 ?

  <1-255>  Effective bandwidth metric (Loading) where 255 is 100% loaded


R1(config-router)#default-metric 1544 10 255 1 ?

  <1-65535>  Maximum Transmission Unit metric of the path


R1(config-router)#default-metric 1544 10 255 1 1500 ?

  <cr>

R1(config-router)#default-metric 1544 10 255 1 1500

Now to redistribute both R1’s connected and RIP routes into the EIGRP AS.

R1(config-router)#redistribute connected

R1(config-router)#redistribute rip

Both R3 and R5 now see the two RIP routes and the 172.12.123.0 /24 network as EIGRP external routes.

R3#show ip route eigrp

D EX  2.0.0.0/8 [170/2172416] via 172.12.13.1, 00:01:10, Serial0/1/0

D EX  22.0.0.0/8 [170/2172416] via 172.12.13.1, 00:01:10, Serial0/1/0

      30.0.0.0/24 is subnetted, 1 subnets

D     30.1.1.0 [90/2172416] via 172.12.13.1, 00:01:02, Serial0/1/0

      172.12.0.0/16 is variably subnetted, 3 subnets, 2 masks

D EX  172.12.123.0/24 [170/21024000] via 172.12.13.1, 00:01:10, Serial0/1/0
R5#show ip route eigrp

D EX  2.0.0.0/8 [170/1662976] via 30.1.1.1, 00:00:37, GigabitEthernet0/0

D EX  22.0.0.0/8 [170/1662976] via 30.1.1.1, 00:00:37, GigabitEthernet0/0

      172.12.0.0/24 is subnetted, 2 subnets

D        172.12.13.0 [90/20514560] via 30.1.1.1, 00:00:37, GigabitEthernet0/0

D EX     172.12.123.0

           [170/20514560] via 30.1.1.1, 00:00:37, GigabitEthernet0/0

We just got word that R5 should not know of any of these EIGRP routes, external or internal, and R3 should continue to see all of them.  Nothing to it, right?  Just write a deny any ACL…

R1(config)#access-list 13 deny any

.. and then apply it in the protocol config and on the appropriate interface.

R1(config)#router eigrp 100

R1(config-router)#distribute-list 13 out fast0/0

Let’s check those routing tables.

R3#show ip route eigrp

D EX  2.0.0.0/8 [170/2172416] via 172.12.13.1, 00:06:13, Serial0/1/0

D EX  22.0.0.0/8 [170/2172416] via 172.12.13.1, 00:06:13, Serial0/1/0

      30.0.0.0/24 is subnetted, 1 subnets

D        30.1.1.0 [90/2172416] via 172.12.13.1, 00:06:05, Serial0/1/0

      172.12.0.0/16 is variably subnetted, 3 subnets, 2 masks

D EX     172.12.123.0/24 [170/21024000] via 172.12.13.1, 00:06:13, Serial0/1/0

 

R5#show ip route eigrp

< no routes >

R5#

R3 still has the routes, but R5 no longer does.  Success!

BUT (and you knew that was coming), what if we now want to filter a single route from R3’s table?  We’d obviously need a different ACL and a different distribute-list.  That brings up three questions…

  • Can we use more than one distribute-list on the same router?
  • If so, can we use more than one distribute-list in the same protocol config?
  • If we can, what’s the net effect to all of our routing tables?

Let’s find out!   We just got the word that R3 shouldn’t have the 30.1.1.0 /24 network in its table, but it should continue to have the external routes.   We’ll write an ACL identifying the route to be filtered while allowing all others…

R1(config)#access-list 33 deny 30.1.1.0 0.0.0.255

R1(config)#access-list 33 permit any

.. and we’ll apply another distribute-list in the EIGRP config without specifying an interface or protocol.

R1(config)#router eigrp 100

R1(config-router)#distribute-list 33 out

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 172.12.13.3 (Serial1/3) is resync: route configuration changed

%DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 30.1.1.5 (FastEthernet0/0) is resync: route configuration changed

The routing table on R3:

R3#show ip route eigrp

D EX  2.0.0.0/8 [170/2172416] via 172.12.13.1, 00:14:27, Serial0/1/0

D EX  22.0.0.0/8 [170/2172416] via 172.12.13.1, 00:14:27, Serial0/1/0

      172.12.0.0/16 is variably subnetted, 3 subnets, 2 masks

D EX     172.12.123.0/24 [170/21024000] via 172.12.13.1, 00:14:27, Serial0/1/0

The 30.1.1.0 /24 route has been successfully removed.  What about the previous distribute-list?  How does R5’s routing table look now?

R5#show ip route eigrp

<no routes>

R5#

The previous distribute-list is still in effect, since it was specifically written to filter route updates leaving fast0/0.  General distribute-list (lists that do not indicate a specific interface or protocol) do not overwrite distribute-lists that specifically mention an interface or protocol.

On occasion, we’ll need to do more than a simple permit or deny when it comes to redistributed routes.  Sometimes we just may need to set different metrics for different routes, and maybe even change an OSPF external route type or two.  We can get those jobs done with route maps, and we’ll start working with those in the next tutorial in this series, which I’ll post on August 15, 2018.

Until then, catch up on the other CCNP ROUTE tutorials on this site.  That page includes every route redistribution tutorial in this series, so get over there and I’ll see you tomorrow!

Check out Chris Bryant’s CCNP ROUTE Study Guide on Amazon, too!

Chris Bryant's CCNP ROUTE Study Guide