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ACL and OSPF problem

I am using the Cisco Network Simulator and I got stuck on the following problem with ACL and OSPF. The lab is as follows:


PC1-R1 is on network (R1 has

R1-R2 is on /30 network

R2-PC2 is on network (R2 has

R1 is using S0/0/0 and R2 is using S0/0/1

The lab is preconfigured with all the IPs and OSPF. The condition is to set ACL to block TELNET traffic from PC2 to R1-PC1 network and permit all other.

Following the instructions the ACL was set up like this:

access-list 100 deny tcp eq 23

access-list 100 permit ip

on R2 s0/0/1 ->ip access-group 100 out.

Once I do this, OSPF stops sending Hellos. If I apply the ACL on F0/0 in, OSPF works.

My question here is, why OSPF stops sending Hellos on S0/0/1 once the ACL is applied?

Am I missing something here, or the example is wrong?

Should it be F0/0 instead of S0/0/1 to fullfill the requirements?

Shouldn't ACL ignore localy generated traffic?

Everyone's tags (2)

ACL and OSPF problem


I posted an example on CLN  with  an ACL denying everything and applied outbound on a link where the OSPF adjacency is happening and you can see that it has no effect on the adjacency which proves that outbound ACLs don't care about router generated traffic.



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Community Member

ACL and OSPF problem

Hi Alain,

You were right. I tested on real 2611 and it worked. It is a bug with the simulator.

I've sent a bug report report to Cisco.

Thanks a milion for your great help.

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