Does Access-List block Routing updates

VTP, Portfast, Spanning Tree and all the other switch related stuff.
Guest

Does Access-List block Routing updates

Post by Guest » Sat Jan 08, 2011 1:26 pm


hi, If I were to put an access-list deny ip any any, would it block any routing updates as well via the dynamic routing protocols.

Guest

Re:Does Access-List block Routing updates

Post by Guest » Sat Jan 08, 2011 1:43 pm


Yes, definitely.You should permit the proper routing protocol packets in the access-list if you want them to pass the access-list.The acl statement permitting the routing protocol should be before the "deny ip any any" statement, of course.Cheers:Istvan

Guest

Re:Does Access-List block Routing updates

Post by Guest » Sat Jan 08, 2011 2:40 pm


So if I were to permit routing updates via BGP, OSPF and RIP what would the access-list be like.Thanks.

Guest

Re:Does Access-List block Routing updates

Post by Guest » Sat Jan 08, 2011 3:17 pm


For OSPF:access-list 100 permit ospf any anyFor EIGRP:access-list 100 permit eigrp any anyFor BGP:access-list 100 permit tcp any any eq 179or access-list 100 permit tcp any eq 179 anydepending on the direction you apply the access-list.Cheers:Istvan

Guest

Re:Does Access-List block Routing updates

Post by Guest » Sat Jan 08, 2011 3:30 pm


If the access list is applied inbound then Istvan is correct that an access list would deny the routing protocol packets unless there is a permit statement for them. However if the access list is applied outbound then the access list will not block the routing protocol packets (no matter whether there is a permit statement for them or not).This is one of the odd things about access lists. An outbound access list does not examine (and will not block) any traffic that is generated by the router itself.HTHRick

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