OSPF interArea: /32 prefixes

ccnpninjaccnpninja Senior MemberEuropeMember Posts: 1,010 ■■■□□□□□□□
Hi,
I have 2 routers R2 and R3 in a point-to-point serial connection. OSPF is configured.
R2 is getting interArea routes forwarded by R3. I still don't know why R2 gets /32 prefixes these routes.

example on R2:
" 192.168.9.0/32 is subnetted, 1 subnets
O IA 192.168.9.1 [110/65] via 172.16.23.3, 00:01:09, Serial0/1 "

although the subnets are configured with /24 prefix.
Any ideas? and how to advertise the correct subnet mask?

Comments

  • TurgonTurgon Banned Posts: 6,308 ■■■■■■■■■□
    ccnpninja wrote: »
    Hi,
    I have 2 routers R2 and R3 in a point-to-point serial connection. OSPF is configured.
    R2 is getting interArea routes forwarded by R3. I still don't know why R2 gets /32 prefixes these routes.

    example on R2:
    " 192.168.9.0/32 is subnetted, 1 subnets
    O IA 192.168.9.1 [110/65] via 172.16.23.3, 00:01:09, Serial0/1 "

    although the subnets are configured with /24 prefix.
    Any ideas? and how to advertise the correct subnet mask?

    Check the interfaces associated with these OSPF routes. Solutions can include ip ospf network point-to-point, area range or redistribute connected.
  • ccnpninjaccnpninja Senior Member EuropeMember Posts: 1,010 ■■■□□□□□□□
    yes, one networker told me to configure "ip ospf network point-to-point" under loopbacks. In fact, this behaviour manifests for loopback interfaces.
    issue resolved.
  • dtlokeedtlokee Member Posts: 2,378 ■■■■□□□□□□
    The issue may be due to the "ppp peer-neighbor-route" command. This causes PPP to add a route to the neighbor that is a /32 route. This can then be advertised into OSPF if the network command is not specific to jsut the local interface IP address.

    Here is the neighbor route (the 172.16.254.33/32):
    Router#sh ip route conn
         172.16.0.0/16 is variably subnetted, 6 subnets, 4 masks
    C       172.16.254.32/30 is directly connected, Multilink1
    C       172.16.254.33/32 is directly connected, Multilink1
    

    Because it shows up as connected it is subject to advertisement by OSPF. if you used the command "network 172.16.254.32 0.0.0.3 area 0" both the /30 route and the /32 route would be advertised into OSPF. The resolution would be to use a network command with the local interface IP address and a 0.0.0.0 wildcard mask.
    The only easy day was yesterday!
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