SNMP discovery between vlans?

[tahequivoice]

We have a customer with Cisco switches and a Cisco WLC with AP's. He is trying to use a program that uses snmp discovery and we thought it might be the wireless, but found out through wireshark that the SNMP discovery isnt working between vlans.  What do I need to look for on the switches to allow this to work?

[Reza Sharifi]

Have a look at the reference guide for configuring SNMP on your devices.

http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/50sg/configuration/guide/snmp.html

HTH

[tahequivoice]

SNMP to the switch is working fine, the problem is snmp discovery from a server to clients on a different VLAN, which is preventing the clients on the wireless Lan from being discovered.

We have a server on vlan 3, the Wireless on Vlan 10 where the WLC i connected to. All traffic flows through the WLC no matter what vlan it is on. We hooked a laptop to VLAN 10 and did a wireshark capture and we are not seeing any SNMP discovery packets, if we put it on vlan 3, we are seeing them.  It acts like something is blocking SNMP but we dont have anything being blocked any where.

[glen.grant]

  I believe you are only going to be able to get snmp to the controller itself if thats what you are asking.  Not sure you are going to see anything on the ap's directly  as all ap traffic talks to the WLC thru an ecrypted tunnel .  The controller itself will give you any info about the aps' you need .  If you can't get to the controllers then verify the community strings  match in the controllers and your server.  Also check for like snmp acl's on the controllers that might be blocking anything. To be honest I don't know if you can discover or not thru the encrypted ap tunnel then out to any device hung off the ap . Most of that info should come from the controller itself.

[tahequivoice]

We aren't seeing any SNMP traffic across the VLAN. We have it setup on a montoring port and no SNMP traffic is going across the VLAN. If we swtich the port to VLAN 3 we can see the SNMP traffic.  It doesnt appear that the SNMP traffic is even getting to the WLC across the swtich.  This is really an odd one though, I can reach the WLC from our Monitoring system via SNMP just fine. So why would no snmp packets show up locally?

[glen.grant]

   You would have to find out what switch is doing the routing for those vlans and make sure there are no acl's blocking snmp traffic between them , other than that  it would not be blocked . SNMP would be like any other traffic .