Keepalive on Giga Interface

[yabilteryst]

Hi all,

I was faced to a major issue on my LAN due to err_disable on several 2950s connected on two 6513.

After a problem on a GBIC on the 6513, we replaced it and when we switched on the interface,

all interfaces of 2650 connected on this 6513 were down due to err_disable.

I checked the syslog and err_disable was due to a keepalive packet loop-back.

I check on BugTool and there is a bug referenced about, CSCeg58877.

This bug seems to be applicable to our configuration.

I would like someone explains me why keepalive is implemented on interface and how it's work exactly.

I searched on cisco.com about "Loop Reply Receipts" but explanations are really poor.

Many thanks in advance.

[gpulos]

this could be due to an incorrect cable used for that connection.

you can disable the keepalives per port with the 'no keepalives' command.

keepalive packets are used for 'Balun detection' on copper interfaces and are enabled by default on all interfaces.

note: baluns are used on power line interfaces to couple signals onto the power line. balun stands for 'BALancing/UNbalancing'

note: disabling keepalives on fiber interfaces should reduce the likelihood of a temporary loop causing a partial network outage.