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Community Member

Tuning EEM parameters

Hi

We have the following config in place to install a backup route when the primary goes down and vice-versa.

rtr 10

type echo protocol ipIcmpEcho 10.160.127.254

timeout 1000

frequency 3

request-data-size 32

rtr schedule 10 life forever start-time now

!

event manager applet EEM_PRIMARY_DOWN

event snmp oid 1.3.6.1.4.1.9.9.42.1.2.9.1.6.10 get-type exact entry-op eq entry-val 1 exit-op eq exit-val 2 poll-interval 3

action 1.0 syslog msg "Primary link DOWN - Failing over to backup link"

action 1.1 cli command "enable"

action 1.2 cli command "configure terminal"

action 1.3 cli command "no ip route 111.111.111.0 255.255.255.0 10.160.127.254"

!

event manager applet EEM_PRIMARY_UP

event snmp oid 1.3.6.1.4.1.9.9.42.1.2.9.1.6.10 get-type exact entry-op eq entry-val 2 exit-op eq exit-val 1 poll-interval 3

action 1.0 syslog msg "Primary link UP - Failing over to primary link"

action 1.1 cli command "enable"

action 1.2 cli command "configure terminal"

action 1.3 cli command "ip route 111.111.111.0 255.255.255.0 10.160.127.254"

!

Even if there is a single echo failure detected by RTR. It triggers the event. This is what log states:

Jul  7 06:28:53.361: %HA_EM-6-LOG: EEM_PRIMARY_DOWN: Primary link DOWN - Failing over to backup link
Jul  7 06:28:56.361: %HA_EM-6-LOG: EEM_PRIMARY_UP: Primary link UP - Failing over to primary link

Jul  7 06:44:53.741: %HA_EM-6-LOG: EEM_PRIMARY_DOWN: Primary link DOWN - Failing over to backup link
Jul  7 06:44:56.741: %HA_EM-6-LOG: EEM_PRIMARY_UP: Primary link UP - Failing over to primary link

Jul  7 08:59:03.048: %HA_EM-6-LOG: EEM_PRIMARY_DOWN: Primary link DOWN - Failing over to backup link
Jul  7 08:59:06.048: %HA_EM-6-LOG: EEM_PRIMARY_UP: Primary link UP - Failing over to primary link

Jul  7 12:01:52.248: %HA_EM-6-LOG: EEM_PRIMARY_DOWN: Primary link DOWN - Failing over to backup link
Jul  7 12:01:58.256: %HA_EM-6-LOG: EEM_PRIMARY_UP: Primary link UP - Failing over to primary link

I tried changing the values of "rtr frequency" and "event snmp oid poll-interval" but the whenever the event applet is polled and the most recent echo has missed, event is triggered.

1. Can this be optimised?

2. Is there a way to trigger the event only when X echos are missed in Y seconds i.e. 3 echos are missed in 16 seconds based on the timers above.

Thanks.

7 REPLIES
Cisco Employee

Re: Tuning EEM parameters

Hmmm, using the SNMP object you're using, no. This object will change the moment a timeout occurs.  What version of IOS is this?

Community Member

Re: Tuning EEM parameters

Thanks for answering.

Its Cisco 6506 running 12.2(18)SXF15, RELEASE SOFTWARE (fc1)

Cisco Employee

Re: Tuning EEM parameters

With this version of code, it will not be possible to do what you want in applet code.  If you can configure object tracking for these IP SLA collectors (with delay down), you can use Tcl to watch the ouput of "show track" to see if the collectors have timed out.  I don't have SXF15 handy with which to test, but it should be doable.  Is object tracking available for you?

Community Member

Re: Tuning EEM parameters

No the current IOS version doesn't support "ip sla" or object tracking based on RTR. Its a production system so a quick IOS upgrade just for this reason is not an option.

Seems I cann't eliminate these false alarms. I will try tunning the parameters "frequency" and "poll-interval" to get the least number of false alarms while ensuring failover is not too slow as well.

Cisco Employee

Re: Tuning EEM parameters

You could still do this with Tcl and the output of "show rtr coll" and "show rtr oper".  If the operational state is timeout, and the number of timeouts has increased over your xOfy threshold, then you can perform the actions.  This will involve you saving the current number of timeouts in an EEM context.  Is Tcl something you can use on this switch?

Community Member

Re: Tuning EEM parameters

Thanks Joe !

Sounds interesting. TCL script will monitor a parameter in the output of "show rtr coll" or "show rtr oper" and will trigger EEM action only when the X timeouts in Y seconds condition is met.  I will try this in test lab first.

Can you point me to an example script for this or similar scenario.

Cisco Employee

Re: Tuning EEM parameters

This version uses the "show rtr" commands to only run the required commands when the number of timeouts reaches a threshold.  You'll need to register two environment variables:

event manager environment rtr_watch_id 1

event manager environment rtr_watch_threshold

Where is your X value (i.e. how many timeouts do you want before the commands are run).

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