Subnet filtering on OSPF

[jealvarez]

One of our modem servers (Lucent Max) is sending route information for 0.0.0.0/0 and 10.0.0.0/8 via OSPF. Our core router (Cisco 7507 w/IOS 12.2.7a) accepts them even though these are not on the OSPF network list. Is there a way to force the router to ignore these routes? Other routes from that modem

server are correct and should be acceptet. The 0.0.0.0/0 route seems to be advertised by default on the modem server (there is no option to turn it off). The 10.0.0.0/8 is real but is for a private subnet that should not go beyond the modem server.

[donewald · Accepted solution]

Try a distribution list (inbound) on the interface your modem server is connected to:

router(config)#access-list 1 deny 0.0.0.0 255.255.255.255

router(config)#access-list 1 deny 10.0.0.0 255.255.255.255

router(config)#access-list 1 permit any

router(config)#router ospf 1

7500-R4(config-router)#distribute-list 1 in

Hope this helps,

Don

[jealvarez]

Thanks. That worked very well. Wound up using 0.255.255.255 on the mask.