redistribution_frenzy

I am going to begin setting up my lab with RIP on the NBMA, EIGRP from R5 to R1, and OSPF off the NBMA spoke R3. This requires 2 ASBR’s, see what issues I come up with along the way, and try to use debugs and show commands before I go to training materials for answers. I am planning on redistributing both OSPF on R1 and EIGRP on R5 into RIPv2 on the ‘WAN’ network, and see if not only the RIP routers can see it, but again if R4 and R5 can learn of each others loopsbacks and be able to ping each others loopbacks being redistributed (hopefully) to all nodes on the network.

The ultimate goal is to see if it is possible to use all protocols, so I can continue to learn how best they work together, and using static routing if necessary to get Layer 3 connectivity across the topology (for now).

A few things I wanted to mention right up front as I am configuring routers:

  • One thing to note, remember in an NBMA, “no ip split-horizon” is needed on the hub(s) interface(s) pointed to the spokes, much alike the distance vector proto EIGRP
  • Through mistakes I made adding the wrong networks to the wrong protocols (172.12.15.0 to RIP instead of EIGRP on R1 for example), I wanted to note that in the event your in a situation where “show run” doesn’t work on the CLI to view what networks are configured where, “show ip proto” can be used to view what networks are routing for what protocol

I also ran into a behavior that was a typo but turned into a learning opportunity, I accidentally typed the interface IP rather than a network number into router configuration, and both “show ip proto” :

R4(config-router)#network 172.12.34.4 0.0.0.255 area 34
R4(config-router)#
*Jan  9 04:27:19.303: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on FastEthernet0/1 from LOADING to FULL, Loading Done

R4(config-router)#do sho ip proto
*** IP Routing is NSF aware ***

Routing Protocol is “ospf 1”
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Router ID 172.12.44.4
  Number of areas in this router is 1. 1 normal 0 stub 0 nssa
  Maximum path: 4
  Routing for Networks:
    172.12.34.0 0.0.0.255 area 34 <- Corrected my host address to a network address
  Routing Information Sources:
    Gateway         Distance      Last Update
  Distance: (default is 110)

R4(config-router)#

And it also shows this in the ‘router ospf 1’ section in the running configuration, however I always prepare for show run not to be available for exams:

!
router ospf 1
 network 172.12.34.0 0.0.0.255 area 34
!

So it should be a legal command if asked, but of course that was a mistake and should not be used as a method for configuration unless intended to.

Another thing I found, making a virtual link to Area 0 between R3 and R4, I accidentally entered “area 34 virtual-link 4.4.4.4” on R3 because R3 was the ABR in Area 0, but now R4 is the simulated ABR in this topology so when I entered 4.4.4.4 no virtual-link came up. I corrected the mistake, and let see what happens:

R3(config-router)#no area 34 virtual-link 4.4.4.4
R3(config-router)#
R3(config-router)#area 34 virtual-link 172.12.44.4
R3(config-router)#
*Mar  1 15:52:06.522: %OSPF-5-ADJCHG: Process 1, Nbr 172.12.44.4 on OSPF_VL1 from LOADING to FULL, Loading Done
R3(config-router)#

And there is our virtual-link.

Now at this point R3 can see the OSPF and RIP networks, and R1 can see the RIP and EIGRP network, however R4 and R5 can only see their own protocols network, so time for some redistribution.

First I am going to redistribute OSPF routes into RIP on R3, and will leave the output from ? to so options as I go along, so we know what option we have to play with:

R3#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R3(config)#router rip
R3(config-router)#redistribut ospf ?

  <1-65535>  Process ID

R3(config-router)#redistribut ospf 1 ?

match      Redistribution of OSPF routes
metric     Metric for redistributed routes
route-map  Route map reference
vrf        VPN Routing/Forwarding Instance
<cr>

R3(config-router)#redistribut ospf 1 metric ?

  <0-16>       Default metric
transparent  Transparently redistribute metric

R3(config-router)#redistribut ospf 1 metric 2
R3(config-router)#sh ip route ospf

Three important things to point out here:

  • You must define the process # in the redistribute command
  • Notice the Default metric can be 0-16, this defines how many hops from the ASBR to the destination network from the ASBR
  • Redistribution is where you will use ‘match’ for ACL filtering of routes, and ‘route-map’ as another way to filter traffic (next topics I will be studying)

So lets see how routes look on R1 which is the next hop router:

R1(config-router)#do show ip route
(Route codes redacted)

Gateway of last resort is not set

     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback1
     2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
R       2.2.2.2/32 [120/1] via 172.12.123.2, 00:00:10, Serial0/0
R       2.0.0.0/8 [120/1] via 172.12.123.2, 00:01:32, Serial0/0
     3.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
R       3.3.3.3/32 [120/1] via 172.12.123.3, 00:00:15, Serial0/0
R       3.0.0.0/8 [120/1] via 172.12.123.3, 00:02:35, Serial0/0
     4.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
R       4.4.4.4/32 [120/2] via 172.12.123.3, 00:00:16, Serial0/0
R       4.0.0.0/8 [120/2] via 172.12.123.3, 00:02:36, Serial0/0
     5.0.0.0/24 is subnetted, 1 subnets
D       5.5.5.0 [90/156160] via 172.12.15.5, 01:08:30, FastEthernet0/1
     172.12.0.0/16 is variably subnetted, 4 subnets, 2 masks
R       172.12.34.0/24 [120/1] via 172.12.123.3, 00:00:23, Serial0/0
R       172.12.44.4/32 [120/2] via 172.12.123.3, 00:00:23, Serial0/0
C       172.12.15.0/24 is directly connected, FastEthernet0/1
C       172.12.123.0/24 is directly connected, Serial0/0
R1(config-router)#

So there is some confusion in this routing table that I wanted to highlight, as we have 1 OSPF Area showing a metric of 1, and we also have a host address rather than Area 0’s network in the route table:

  • 172.12.34.0/24 network is directly connected on R3 and directly connect routes have an Administrative Distance of 1, so it is reporting that as it’s hop count to that network to R1, while the other routes off in OSPF land have the default metric 2
  • It is showing my virtual-link’s remote IP address rather than Area 0’s network that I entered as “network 172.12.44.0 0.0.0.255” in router configuration on R4, so it appears the virtual-link settings are somehow over-riding the OSPF configuration?

One thing I noticed along the way is my NBMA spokes R1 and R2 are not getting any RIP routes, however the Hub and soon to be ASBR R1 is seeing all routes as can be seen above.

I did issue ‘no ip split’ on the Hub but that didn’t do the trick, and I am calling it a night, this seems like a good place to pick up when I am fresh.

Late night edit:

I can’t stop thinking whether it would still show that host address or how the route table on R1 will change if I remove the accidental host address on R4’s OSPF configuration, and add the route as a network:

R4#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R4(config)#router ospf 1
R4(config-router)#no network 172.12.44.4 0.0.0.0 area 44
R4(config-router)#
*Jan  9 08:46:41.439: %OSPF-5-ADJCHG: Process 1, Nbr 3.3.3.3 on OSPF_VL0 from LOADING to FULL, Loading Done
R4(config-router)#network 172.12.44.0 0.0.0.255 area 44
R4(config-router)#
*Jan  9 08:47:03.483: %OSPF-6-AREACHG: 172.12.44.0/24 changed from area 0 to area 44
R4(config-router)#
ASR#r1
Trying R1 (100.1.1.1, 2001)… Open

R1>en
Password:
R1#show ip route
(Route codes redacted)

Gateway of last resort is not set

     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback1
     2.0.0.0/32 is subnetted, 1 subnets
R       2.2.2.2 [120/1] via 172.12.123.2, 00:00:12, Serial0/0
     3.0.0.0/32 is subnetted, 1 subnets
R       3.3.3.3 [120/1] via 172.12.123.3, 00:00:09, Serial0/0
     4.0.0.0/32 is subnetted, 1 subnets
R       4.4.4.4 [120/2] via 172.12.123.3, 00:00:09, Serial0/0
     5.0.0.0/24 is subnetted, 1 subnets
D       5.5.5.0 [90/156160] via 172.12.15.5, 00:01:30, FastEthernet0/1
     172.12.0.0/16 is variably subnetted, 4 subnets, 2 masks
R       172.12.34.0/24 [120/1] via 172.12.123.3, 00:00:10, Serial0/0
R       172.12.44.4/32 [120/2] via 172.12.123.3, 00:00:10, Serial0/0
C       172.12.15.0/24 is directly connected, FastEthernet0/1
C       172.12.123.0/24 is directly connected, Serial0/0
R1#

This change in the route table makes no sense to me, and I assume it is due to R3 considering that virtual link to be a logical cable, the same way an Etherchannel considers a bundle of physical cables to be a single logical cable.

So just for giggles I wanted to see what tables would look like had I just removed the virtual-link between R3 and R4 all together, and got some really interesting results from all my routers:

R1#show ip route
(Route codes redactied)
Gateway of last resort is not set

     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback1
     2.0.0.0/32 is subnetted, 1 subnets
R       2.2.2.2 [120/1] via 172.12.123.2, 00:00:11, Serial0/0
     3.0.0.0/32 is subnetted, 1 subnets
R       3.3.3.3 [120/1] via 172.12.123.3, 00:00:07, Serial0/0
     5.0.0.0/24 is subnetted, 1 subnets
D       5.5.5.0 [90/156160] via 172.12.15.5, 00:28:43, FastEthernet0/1
     172.12.0.0/24 is subnetted, 3 subnets
R       172.12.34.0 [120/1] via 172.12.123.3, 00:00:07, Serial0/0
C       172.12.15.0 is directly connected, FastEthernet0/1
C       172.12.123.0 is directly connected, Serial0/0
R1#
ASR#3
I have no idea what caused this behavior, but the only OSPF route being Redistributed into RIP is 172.12.34.0/24, and that is because it is a directly connected network:
R3#show ip route
(Route codes redacted)

Gateway of last resort is not set

     1.0.0.0/32 is subnetted, 1 subnets
R       1.1.1.1 [120/1] via 172.12.123.1, 00:00:21, Serial0/2
     2.0.0.0/32 is subnetted, 1 subnets
R       2.2.2.2 [120/2] via 172.12.123.2, 00:00:21, Serial0/2
     3.0.0.0/32 is subnetted, 1 subnets
C       3.3.3.3 is directly connected, Loopback3
     172.12.0.0/24 is subnetted, 3 subnets
C       172.12.34.0 is directly connected, FastEthernet0/1
R       172.12.15.0 [120/1] via 172.12.123.1, 00:00:21, Serial0/2
C       172.12.123.0 is directly connected, Serial0/2
R3#

I tried to ping the two networks we lost from R3 to R4 which is connected by an Ethernet cable, and all packets were lost, and also can be seen of course is that 172.12.340/24 is directly connected and configured in OSPF so it will allow it to be Reditributed. So I took one last look at R2 just to complete the confirmation of this OSPF behavior:

R2#show ip route
(Route codes redacted)

Gateway of last resort is not set

     1.0.0.0/32 is subnetted, 1 subnets
R       1.1.1.1 [120/1] via 172.12.123.1, 00:00:02, Serial0/0
     2.0.0.0/32 is subnetted, 1 subnets
C       2.2.2.2 is directly connected, Loopback2
     3.0.0.0/32 is subnetted, 1 subnets
R       3.3.3.3 [120/2] via 172.12.123.3, 00:00:02, Serial0/0
     172.12.0.0/24 is subnetted, 3 subnets
R       172.12.34.0 [120/2] via 172.12.123.3, 00:00:02, Serial0/0
R       172.12.15.0 [120/1] via 172.12.123.1, 00:00:02, Serial0/0
C       172.12.123.0 is directly connected, Serial0/0
R2#

So in theory I was correct that R4 needed to have a virtual-link to its Area 0 loopback interfaces to get it to propagate routes, however I think I am going to make a loopback on R3 in Area 0, then turn the virtual-link to R4 into a random area and see if we can straighten this out.

I forgot that it would allow OSPF learned routes from R3 to be advertised to to R4 and other ABR’s in Area 0 to learn, and I would need it going the other way, however I want to keep the NBMA RIP. Time to get some dirt under the finger nails on the next lab.