Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements
Webcast-Catalyst9k
New Member

SNMP polling discovering interfaces which don't exist

I noticed on our network monitoring server that it's detecting an Ethernet0/0 interface on various routers on our network. The problem is these routers don't have an ethernet interface, they only have fast ethernet. I have seen it so far on a 1760 and a 1721, running different IOS. To eliminate the monitoring software, I used a MIB browser to walk the interfaces on the router, and sure enough, it comes up with this ethernet 0/0. But if I look at the config on the router, there is no ethernet interface. Also, the monitoring station also shows the interface in an up, up status. How can this be? Is there a known issue with this happening that I have not heard about?

5 REPLIES
Cisco Employee

Re: SNMP polling discovering interfaces which don't exist

What object(s) is reporting Ethernet0/0 as existing? Try doing an snmpget on sysDescr.0 and sysName.0 followed by a walk of ifDescr. We have seen issues where certain interfaces stick in the ifTable until a reboot, but I don't believe we/ve had any issues with a phantom Ethernet0/0 interface showing up.

New Member

Re: SNMP polling discovering interfaces which don't exist

The ifDesc shows "Ethernet0/0", and the MAC address field shows up as 0000.0000.0000. The admin status shows as up, up. The sysDesc0 shows that its a 1700 series router. We have several that are doing this.

Cisco Employee

Re: SNMP polling discovering interfaces which don't exist

I still don't see any bugs on this, but it does sound like a real problem given the strange MAC address. What version of IOS is this particular 1700 running? Can you reload one of these 1700s to see if the phantom interface goes away?

New Member

Re: SNMP polling discovering interfaces which don't exist

I cannot reload them, as they are production routers. I don't think it will matter, as I've counted at least two dozen that are showing this phantom interface. So far they are running 12.3(11)T4 for code. However, I have seen a few routers running this code that do not display the phantom interface.

Cisco Employee

Re: SNMP polling discovering interfaces which don't exist

I still cannot find a bug that explains this behavior. I suggest you open a TAC service request and include a complete problem description along with a show tech from one of these 1700s and an snmpwalk of the ifTable. This will most likely require a recreate.

144
Views
0
Helpful
5
Replies
CreatePlease to create content