Router cannot send icmp packet

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Nov 6th, 2009
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we have cisco 878 series router,we try to make an icmp packet from vlan 1 and the client is the same vlan,when we try this so there was no icmp packet generated from router.I see the arp of client but i couldnt ping from router.What could be the problem.

Thank you

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mike_guy29 Fri, 11/06/2009 - 05:14
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Could be any number of problems. Is the client directly connected? Are there any ACLs blocking ICMP? Is the router sourcing the ICMP from the correct interface. Does the client you are trying to ping have the correct settings (default gateway etc).

Perhaps you can provide some more information and configuration (minus sensitive lines such as passwords).



tdorduncu Fri, 11/06/2009 - 06:13
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Yes its same subnet with client.When we try to ping through switch, there was no problem.When we try directly from router,it fails.

mike_guy29 Fri, 11/06/2009 - 06:41
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So are you saying the following...

Router----Switch----PC = ICMP works

Router----PC = ICMP not working?

If so sounds to me possibly like a cabling issue. You may require a crossover cable to connect the PC to the router depending upon model etc. Is this the problem or is is specifically to do with ICMP?

Can the client PC communicate at all when directly connected?



tdorduncu Fri, 11/06/2009 - 07:01
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Yes,it can.I can send telnet from router to the clients tcp port that it listens.It's ok,But whe i try to send an icmp from router so client didnt reply me.But i can send an icmp behind the router.I suppose that router not forwards self generated icmp packets,i opened all related debugs ( arp,icmp etc.)but i didnt see any arp req response.

mike_guy29 Sun, 11/08/2009 - 13:46
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No there should be no reason the ICMP from the router is blocked. Can you clarify when you say "But I can send ICMP behind the router" exactly what you mean. Could it be an issue with the clients firewall?

tdorduncu Sun, 11/08/2009 - 23:16
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No,client has no firewall.i can send icmp like this.There was a wan network between two routers.


i couldnt find the reason but it works now.Thank you


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