ICMP Unreachables on Layer3 Switch

[Philip91]

Hello,

i try to ping an unreachable host to generate an icmp unreachable message on our 3750. I also tested it with an 6500. It didn´t work.

ip unreachables on the Layer3 Interface is enabled

Then I tested it with a basic Router and it worked fine. On Nexus 7k it worked also.

Does everybody know if an Layer3 Switch generally sends ICMP Unreachables ?

To me it should because of:

sh ip interface vlan 40

ICMP unreachables are always sent

Thanks

Philip

[Raju Sekharan]

Do you have any  mls rate-limiter, control-plane policing, acl or qos blocking ICMP un-reachable messages

Thank you

Raju

[Philip91]

No nothing of that

Can i verify with an debug command that my Layer3 Switch sends out the packets or not ?

I sniffed at the network card of my computer with wireshark and there were no icmp reply

[Raju Sekharan]

You can do " deb ip icmp" and check if you are sending unreachables

Thank you

Raju

[cadet alain]

Hi,

if you want to see debugs for transit traffic you'll have to disable ip cef for the interfaces with no ip route-cache cef command

Regards.

Alain

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[Philip91]

i made an debug on the switch and there is no output of any unreachable packets.

in the debug of the router i thought every unreachable message.

Is that a correct behavior ?

[Raju Sekharan]

What is the IP you are trying to ping?

Can you collect below output from 6500

1. Show ip cef

2. Show ip traffic

Thank you

Raju

[Philip91]

i did it on an 3750G

show ip cef 192.168.251.200
%IPv4 CEF not running

show ip traffic

ICMP statistics:

  Sent: 0 redirects, 0 unreachable, 15 echo, 73360 echo reply
        0 mask requests, 0 mask replies, 0 quench, 0 timestamp
        0 info reply, 0 time exceeded, 0 parameter problem
        0 irdp solicitations, 0 irdp advertisements