3

OSPF Topology

Problem Description

I am having an issue with LSA Type 3's, on R7 in the topology i have 4 loopback addresses

Loopback1 is up, line protocol is up
Internet address is 192.168.100.1/28
Loopback2 is up, line protocol is up
Internet address is 192.168.100.17/28
Loopback3 is up, line protocol is up
Internet address is 192.168.100.33/28
Loopback4 is up, line protocol is up
Internet address is 192.168.100.49/29

I change the OSPF network type on all these links to : Network Type POINT_TO_POINT

On R7 under : router ospf 123, i have

network 192.168.100.0 0.0.0.255 area 44

on r6 i have the command

area 44 range 192.168.100.0 255.255.255.0 

R6's routing table

R6#show ip route | i 168.100

   192.168.100.0/24 is variably subnetted, 5 subnets, 2 masks
   O       192.168.100.0/28 [110/11] via 192.168.1.129, 00:00:02, FastEthernet0/1
   O       192.168.100.0/24 is a summary, 00:00:02, Null0
   O       192.168.100.16/28 
   O       192.168.100.32/28 
   O       192.168.100.48/28

As expected, i can see my summary with Null0 and the subordinate routes - all ok here.

but here is R5

   R5#show ip route | i 168.100
 192.168.100.0/24 is variably subnetted, 5 subnets, 2 masks
   O IA    192.168.100.0/28 [110/21] via 192.168.1.2, 00:01:50, FastEthernet0/1
   O IA    192.168.100.0/24 [110/21] via 192.168.1.2, 00:02:36, FastEthernet0/1
   O IA    192.168.100.16/28 [110/21] via 192.168.1.2, 00:01:40, FastEthernet0/1
   O IA    192.168.100.32/28 [110/21] via 192.168.1.2, 00:01:30, FastEthernet0/1
   O IA    192.168.100.48/28 [110/21] via 192.168.1.2, 00:01:20, FastEthernet0/1

This is not meant to happen, i am only meant to see

   O IA    192.168.100.0/24 [110/21] via 192.168.1.2, 00:02:36, FastEthernet0/1

its the same all the way along to r1

R1#show ip route | i 168.100 
     192.168.100.0/24 is variably subnetted, 5 subnets, 2 masks
O IA    192.168.100.0/28 [110/61] via 10.1.1.2, 00:03:04, FastEthernet0/0
O IA    192.168.100.0/24 [110/61] via 10.1.1.2, 00:03:50, FastEthernet0/0
O IA    192.168.100.16/28 [110/61] via 10.1.1.2, 00:02:54, FastEthernet0/0
O IA    192.168.100.32/28 [110/61] via 10.1.1.2, 00:02:44, FastEthernet0/0
O IA    192.168.100.48/28 [110/61] via 10.1.1.2, 00:02:34, FastEthernet0/0

The reason area 0 is where it is, i was practicing virtual links

if you can shed any light on why the subordinate rotes are being advertised i would be very grateful

Andy

  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 9 '17 at 2:06
2

Your topology violates OSPF rules. All your areas must be adjacent to area 0. Area 44 and 50 are not adjacent to area 0.

| improve this answer | |
  • I agree its poor design and should only be used as a last resort. However it is possible to have areas that are not adjacent to area 0 with the use of virtual links. However I will try and recreate the lab with better/proper network design. – psniffer Aug 23 '14 at 11:49
  • I would argue that virtual links makes them adjacent. But in any case, that wasn't part of the design you presented. – Ron Trunk Aug 23 '14 at 20:38
  • Firstly thanks for taking the time to answer, I appreciate it. I managed to get it working, I did very briefly mention the virtual links at the end of the original problem. The problem turned out to be a miss configuration of the virtual links. Thanks again. – psniffer Aug 23 '14 at 20:43
  • Ah yes, I see that now. I saw the topology diagram and jumped to conclusions. Sorry for not reading more carefully. Glad you got it working. – Ron Trunk Aug 24 '14 at 0:18

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