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New Member

Strange SNMP behavior with 12.1(22)EA4

So this is the most bizzare behaviour with a very simple configuratio to read MRTG stats off little WS-C2950-24 switch running 12.1(22)EA4

There is absolutely no security and no fancy stuff. Just the most simple configuration.

IF the MRTG host is ON THE SAME network number as the vlan1 interface the switch responds to SNMPWALK just fine and everything works.

However if the MRTG host is NOT on the same network number as the vlan1 interface then the switch is totally dead to ANY snmp packets. It does NOT respond at all, debug does NOT register anything at all, however wireshark does see the incoming packets from the MRTG host with absolytely NO reponse back from the switch?

Total IOS bug or there is a credible "feature" which doesn't allow snmp as long as it has to go via default gateway (not local to the switch net that is)

Thanks

~B

4 REPLIES

Strange SNMP behavior with 12.1(22)EA4

If a switch answer on the same lan, withing the same ip range, it talks direct. If it talks to a remote network it answers to the default gateway.

That gateway defined on the switch, has to know a route to the destination network.

If your host is 10.10.10.1 then the default gateway of your switch should know the route to the 10;10.10.0 network.

Cheers,

Michel

New Member

Strange SNMP behavior with 12.1(22)EA4

Thank you, enjoyed reading your post

I do like to keep a sense of humor in this profession... but no, that's not it.

Strange SNMP behavior with 12.1(22)EA4

Maybe I explained the obvious :-), sorry, but you be suprised to find how many "IT people" just don't understand on L2, L3 how IP communications work.  

OK, then I don't have an idea what is wrong. Sorry.

It is however normal for the IOS to drop the SNMP packets if the switch doesn't know the route to the network where those packets came from.

Cheers,

Michel

New Member

Strange SNMP behavior with 12.1(22)EA4

I agree Mike; the "IT pride" is a wide spread issue in this line of work that leaves a lame taste of the profession.

Long story short. It was probably corrupt image though there isn't a definitive way to confirm that (again, I try to stay away from the IT people assumptions).

What is back and white is the remedy. After formatting the flash and uploading the SAME image the SNMP problem went away.

Thanks

~B

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