4

I have 2 routers running OSPF. Each router has a vlan configured with an ip from a /29. The routers are directly connected. I also have a loopback configured on each router with a /30.

Example:

Router1 vlan ip: 1.1.1.13/29 / Loopback: 1.1.1.1/30

Router2 vlan ip: 1.1.1.10/29 / Loopback: 1.1.1.2/30

I enabled ospf on both interfaces but for some reason, only Router2 is seeing the /29 route and the /30. Router 1 only sees the /30. Here is the ospf route output:

Router1:
#sho ip ospf routes
OSPF routes entries: 1 used, 264191 available
OSPF Regular Routes:

Destination     Mask            Path_Cost       Type2_Cost Path_Type
1.1.1.0    255.255.255.252 0               0          Intra
Adv_Router      Link_State      Dest_Type       State      Tag        Flags
1.1.1.1    1.1.1.1    Network         Valid      0           0400
Paths           Out_Port        Next_Hop        Type       Arp_Index  State
1               lb1             0.0.0.0         OSPF       1          92 00

Router2:
#sh ip ospf routes
OSPF Regular Routes:

  Destination     Mask            Path_Cost Type2_Cost Path_Type
  1.1.1.0    255.255.255.252 0         0          Intra
  Adv_Router      Link_State      Dest_Type State      Tag       Flags
  1.1.1.2    1.1.1.2    Network   Valid      0          0600
  Paths Out_Port  Next_Hop        Type      Arp_Index  State
  1     lb1       0.0.0.0         OSPF      1          92 00

  Destination     Mask            Path_Cost Type2_Cost Path_Type
  1.1.1.8    255.255.255.248 1         0          Intra
  Adv_Router      Link_State      Dest_Type State      Tag       Flags
  1.1.1.2    1.1.1.2    Network   Valid      0          0600
  Paths Out_Port  Next_Hop        Type      Arp_Index  State
  1     v1        0.0.0.0         OSPF      1          92 00

Any reason why ospf wouldn't be picking up the /29 on Router1?

1

I would guess from the output that the devices aren't adjacent, my reasoning behind this is that they are only showing their own locally generated LSA's (next hop of 0.0.0.0).

Are you sure that the /29 is up on both devices and that you have enabled OSPF on the correct links.

As a side note, what platform is this from?

5

I am not sure what your topology looks like, or what exactly your requirements are, but I noticed that there are IP addressing overlaps.

  • The loopbacks are overlapping. 1.1.1.1/30 and 1.1.1.2/30 are in the same subnet.
  • 1.1.1.10/29 and 1.1.1.13/29 are in the same subnet.

Again, without knowing what your topology looks like, I can't say for certain what the issue is, but IP overlaps can cause problems like missing routes (they are missing because of the way the protocol operates, not necessarily because of an error).

2

The routers are only showing the routes connected to their local interfaces as your two subnets have overlapping addresses. Router 1 is missing on of the subnets though.

This is likely a config mistake;

  • Check you have the correct masks on the interfaces them selves
  • Check that OSPF is definably enabled on the missing /29 interface
  • If you are including specific subnet/network statements in your OSPF config, check you had definitely added this subnet and the mask is correct
  • Finally, Post your config!

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