IP SLA Issues

Unanswered Question
Jan 2nd, 2009

Hi all,

I'm having an issues with a IP SLA I created which is controlling a static route. It works but is a little unreliable.

ip sla 1

icmp-echo 87.85.165.76 source-interface Vlan2 (this is a static host I use)

timeout 20000

threshold 2

frequency 30

ip sla schedule 1 life forever start-time now

Periodically when i run "sh track" it shows last change x minutes ago rather than days. The overall status appears to be "up" however.

Track 100

Response Time Reporter 1 reachability

Reachability is Up

15 changes, last change 00:03:23

Latest operation return code: Over threshold

Latest RTT (millisecs) 39

Tracked by:

STATIC-IP-ROUTING 0

Is there a way I can make this less sentative - I would ideally like it to only declare "down" after 30 secs with timeout of 20000 to rule out a flapping link?

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
The_guroo_2 Fri, 01/02/2009 - 08:24

mate you have put the frequency 30 ......its in seconds so after every 30 second it will query.....change that and you will be fine

hope it helps

rasoftware Fri, 01/02/2009 - 08:31

Posted by: rasoftware - 244 Fulwood road

Jan 2, 2009, 8:05am PST

Hi all,

I'm having an issues with a IP SLA I created which is controlling a static route. It works but is a little unreliable.

I originally had it set to 15 but it seemed worse.

Do I understand this correctly -

Target- icmp-echo 87.85.165.76 source-interface Vlan2

Timeout - timeout 20000

Number of failures - threshold 2

Every x seconds - frequency 30

So every 30 secs, request ping within 20000ms, if two fail (threshold) - declare it down?

I always see to have this line in sh track

Latest operation return code: Over threshold

MARTIN STREULE Tue, 01/06/2009 - 04:16

Use the delay command in the "track" part of your config:

delay (tracking)

To specify a period of time to delay communicating state changes of a tracked object, use the delay command in tracking configuration mode. To disable the delay period, use the no form of this command.

delay {up seconds [down seconds] | [up seconds] down seconds}

no delay {up seconds [down seconds] | [up seconds] down seconds}

More info:

http://www.cisco.com/en/US/docs/ios/iproute/configuration/guide/irp_prb_mult_track_ps6441_TSD_Products_Configuration_Guide_Chapter.html

Hope that helps.

Cheers,

Martin

rasoftware Tue, 01/06/2009 - 04:21

Hi Martin,

Thanks I worked this one out - it's been up for 3 days now without reporting a change using the delay up 10 sec down 30 secs.

Stability is key for my config and I only want failover if it been down for a minute or more.

It is much more stable now.

Thanks for the reply.

Pravin Phadte Tue, 01/06/2009 - 06:36

Hi,

Your Question:

Is there a way I can make this less sentative - I would ideally like it to only declare "down" after 30 secs with timeout of 20000 to rule out a flapping link?

Declare down after 30 seconds:

Command "frequency 30"

Rule a flapping link ?

Commadn " timeout 20000" (not sure that what is defined"

-----

Remove the static route if the link is down more than 30 seconds and not flapping.

The flapping can occur in minutes and you link may be up for 5 min and then again down or may be down in 1 min 2wice.

------------

This works great for me 5 min.

Paramites needed:

num-packets 3

frequency 300

remove

timeout 20000

threshold 2

When the route goes off. This will wait for 5 min down to replace the route.

So if your link flaps in this 5 min it will shift to backup unless it gest 3 packests in 5 min probe.

Once its down. It changes it route.

Now best part it will stay on the other route unless gain it recives prove of 5 min stable 3 packtes from the icmp-echo ip.

so if the link flaps on icp-echo ip provided it will not relace the route. Once the link is stable it will replace the route.

Downtime not more than 5 sec,

But for the first swicth over it depends on the frequency.

do decide about the frequesy you need to set.

Hope this helps

Regards,

pravin

rasoftware Tue, 01/06/2009 - 07:34

Thanks Pravin,

I think i've cracked it with the 20000ms, freq 30sec, threshold 2.

Adding delay down 30 sec up 10 has prevented the status changing.

I believe if it missing two pings of a very high latency in 60 sec - it then starts count down - so a max 90 sec before failover. This seems to prevent "flapping" of the route due to a few missed pings when the link is really fine.

The sh track now corresponds to the router uptime, before I was getting a status change every 5 mins or so when the link was fine.

Since I have a VPN working over it - this was causing the tunnel to drop etc which is not good for the terminal users behind it.

I will investigate the "num packets" line as this might provide further more accuracy. I suspect my one just sends a single ping each 30 secs rather than 3 which should provide less false positives

georges.merhej Tue, 02/03/2009 - 03:06

Hello Guys,

Do you have any idea on how to clear the "show track" statistics?

MOE#show track

Track 1

Response Time Reporter 1 reachability

Reachability is Up

57 changes, last change 10:14:49

Latest operation return code: OK

Latest RTT (millisecs) 40

Thanks,

Georges

Pravin Phadte Tue, 02/03/2009 - 04:18

hi,

copy the output for show run sla monitor xxx

config t

no sla monitor xxx

check track it will be 0

then paste back the configs for sla monitor 123

Actions

This Discussion