3850 link state tracking

[chris.smailes]

Just wondering if anyone knows if there is an equivalent of "link state tracking" for the 3850 as this feature is unfortunately not supported in IOS-XE.

I have a pair of 3850's (no ip routing) with servers sitting across the two set to fail-on-fault and I'd like to configure the 3850's so that if the ten-gigabit uplink line protocol goes down then the  gigabit ports will be shut down and then re-enabled if the uplink comes back up.

I've seen posts about ipsla and event manager but that seems complex whereas link state tracking was much simpler to implement.

Thanks very much in advance.

[chris.smailes · Accepted solution]

It turned out to be straightforward:

On each switch using

track 1 interface TenGigabitEthernet1/1/1 line-protocol

event manager applet Uplink-Goes-Down
event syslog pattern "%TRACK-6-STATE: 1 interface Te1/1/1 line-protocol Up -> Down"
action 1 cli command "en"
action 2 cli command "config t"
action 3 cli command "interface range gig 1/0/1 - 48"
action 4 cli command "shut"
action 5 cli command "end"

event manager applet Uplink-Comes-Up
event syslog pattern "%TRACK-6-STATE: 1 interface Te1/1/1 line-protocol Down -> Up"
action 0 wait 18
action 1 cli command "en"
action 2 cli command "config t"
action 3 cli command "interface range gig 1/0/1 - 48"
action 4 cli command "no shut"
action 5 cli command "end"
!

Strictly speaking it could be done without the track command (just using link down message) but track seems to react quicker (it’s the first message you see) and the message is a bit simpler.

There is a delay in re-enabling in case the link is flapping – there seems to be a bug in the EEM version as values of 20s and over just don’t work but I think 18s is OK for now but still looking.

In case you think this is an odd setup nowadays, it is legacy.

When/if we get a VSS pair as distribution switches, the 3850s can then be stacked with MEC from VSS pair  – something to look forward to…but for now as each switch is connected to a different non-virtualised 6800, using stacking would introduce a loop as the connections are still L2.