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How to monitor layer 2 links:



I have two cisco switches, at two different sites, having two Layer 2 ISP links in between these two switches.

How can I monitor if one of both link gets down???

As per my knowledge there are two options 1. STP   2. Ether channel.

In both case we get redundancy but how administrator come to know one of the link is down so he/she could book docket against down link with ISP.

At one side we have Cisco Nexus 7010 and Cisco 2960 at another end. if link is get down in between ISP, port at switch end will not get down, in this case what happen with STP and ether channel case. will that generate logs in this case which can be forwarded to syslog server.

is there any monitoring tool which can be useful in such scenarios ??

in such scenarios what is the best practice to manage the network??


4 Replies 4

Austin Sabio

logging enable

S(config)# logging enable

logging event link-status (global configuration)

S(config)# logging event link-status

logging event link-status (interface configuration)

(config-if)# logging event link-status

logging event trunk-status

(config-if)# logging event trunk-status

show logging

Displays the state of system logging (syslog) and the contents of the standard system logging buffe

logging host <ip-address>

logging trap 6
logging buffered 6

Please rate if helpful. 

Thank you.

you can also use netflow monitor at layer 2


Hi, Thanks for your response...

ok.. layer 2 link status which can generate syslog message & layer 2 netflow.....agreed.

if both layer 2 links are not trunk then ??

if both layer 2 links are in etherchannel ?? & if one link of etherchnnel is down or flapped Portchannel will remain up but how administrator will come to know that one link of that PO is down??


Hi whether there trunk or access the commands engineer_aus provided below applied to each physical interface will raise a syslog to notify your monitoring system that 1 link has dropped , your really not going to get much more at layer 2 to monitor

logging event link-status and the trunk status , they should be applied to physical of PO

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