Basic SNMP Question

[kevmullet]

Hi,

Pretty new to SNMP, the situation I have is a network of cisco catalyst 2950 switches, which I would like to know if a cable is disconnected from any of these.

Is it possible to use SNMP to report when a connection is lost on a port? And what software would you advise to do this?

Cheers

 

[NetRx]

Kiwi syslog server should do the trick. I use Solarwinds on the job but it can be pricy.

Setting up logging on the switches is fairly simple, it's just a matter of what you want to see. For example, if you only want to monitor the uplinks/trunked ports on a 24 port switch and FA0/1 is the uplink:

 Switch(config)#logging trap 3
 Switch(config)#logging <IP address of syslog server>
 Switch(config)#interface range fa0/2-24
 Switch(config-if-range)#no logging event link-status

If you want to monitor all the ports then run the same command above but omit the range command.

Alternatively, if you want the ability to query a device's port status from an application (like Orion from Solarwinds), then you would need to setup SNMP specific command lines:

 Switch(config)#access-list 50 permit ip 192.168.0.50
 Switch(config)#snmp-server host 192.168.0.50
 Switch(config)#snmp-server community <unique string> 50 ro
 Switch(config)#snmp-server enable traps snmp linkdown
 Switch(config)#snmp-server enable traps snmp linkup
 
 OR to only query uplinks/trunks
 --------------------------------
 Switch(config)#access-list 50 permit ip 192.168.0.50
 Switch(config)#snmp-server host 192.168.0.50
 Switch(config)#snmp-server community <unique string> 50 ro
 Switch(config-if)#snmp trap link-status

The ACL 50 will restrict the ability for any unauthorized users to query the 2950s. Furthermore, you can add an 'rw' instead of the 'ro' and get the ability to push configurations from an application. The second piece is useful if you are thinking of setting up any stateful monitoring tools like e-mail alerts, etc... And don't forget, you could log the disconnects directly to the switch using a buffer. Just look-up the logging buffered commands.

Others might be able to point out better syslogging tools. You have plenty of options to say the least. Good luck!

Rich
Network Engineer - CCNA