SSO and the "keepalive-enable" command

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May 29th, 2009
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What does the "keepalive-enable" command do?

So it looks like this command is added by default when you enable SSO on a 6500 series switch with dual SUP720's.

My guess is it is a safety mechanism to communicate keepalives between the two SUP's to monitor for a software freeze.

We We can see below it looks like keepalives are exchanged every 9000 milliseconds, and after 18 timeouts a switchover occurs??

Can't find any explanation of this feature on cisco's docs.


wmrUSNYMD06DC#sh redundancy sta

my state = 13 -ACTIVE

peer state = 8 -STANDBY HOT

Mode = Duplex

Unit = Secondary

Unit ID = 6

Redundancy Mode (Operational) = sso

Redundancy Mode (Configured) = sso

Redundancy State = sso

Maintenance Mode = Disabled

Communications = Up

client count = 76

client_notification_TMR = 30000 milliseconds

keep_alive TMR = 9000 milliseconds

keep_alive count = 0

keep_alive threshold = 18

RF debug mask = 0x0

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Giuseppe Larosa Fri, 05/29/2009 - 09:24
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Hello Louis,

your understanding is correct.

SSO implementation requires the two supervisors to exchange messages through the backplane.

These messages are probably IP packets using 127.0.0.x addresses as it happens when you telnet to a FWSM slot.

I'm not sure that it takes 18 * 9 sec to trigger a switchover

Hope to help



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