OSPF Strange but interesting !!

illusion_rox · ‎09-18-2008

hi guys, pls tell me about this !

if i have 2 routers connected via ethernet link, R1 ip is 10.1.12.1/8 and R2 ip is 10.1.12.2/24, the adjancy doesnt come up,

If the link is p2p the adjancy does come up !!!, why is that so ?? i have gotten the feedback that in p2p subnet mask doesnt match ! but i havent read it anywhere or if i have i dont remember it clearly, can you pls tell me why does it happen, i will be grateful if you could refer me any cisco doc or book or RFC that addresses this issue !!

Thanks

Harold Ritter · ‎09-18-2008

Ovais,

This behavior is compliant with RFC2328 section 10.5:

"However, there is one exception to the above rule: on point-to-point networks and on virtual links, the Network Mask in the received Hello Packet should be ignored."

http://www.ietf.org/rfc/rfc2328.txt?number=2328

Regards

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
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