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denying ping on router

carl_townshend
Frequent Contributor
Frequent Contributor

I was setting up my routers the other day, which are running ospf, I did an access list that denied any icmp trafic from its neighbour router, This causeed ospf to drop this rouyter is that correct ? does it use icmp for its hello ?

5 Replies 5

gwhuang5398
Explorer
Explorer

OSPF doesn't use ICMP for its Hello packets. What's the access list you configured? If you can post the config.

Gary

What protocol does it use for Hellos then ? I think the below port is corrent, It was basically blockinh anything !!

Carl,

OSPF is transported directly over IP and has its own protocol number, which is 89.

Hope this helps. Please rate if it does.

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

By the way, here's where you can find a list of assigned protocol numbers:

http://www.iana.org/assignments/protocol-numbers

Hope this helps,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

Harold Ritter
Cisco Employee
Cisco Employee

Carl,

Did you specify an explicit "permit ip any any" at the end of the ACL? Remember that there is always an implicit "deny ip any any" at the end of any ACL. That is probably why your ospf adjacency went down.

Hope this helps,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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