Tracking Threshold Metric BGP

danabersoch · ‎12-03-2011

Hello,

I am trying to sort out a HSRP solution.

We have two routers that each have their own WAN connection, both receive a default route through EBGP.

On the internal interface we configure HSRP - we used to track through IPSLA but now the liscenes have changed we don't want to spend more money.

So I cannot track interfaces to decrement the standby priority as there is a L2 device between the P2P, neither can I track ip routing for the same reason.

I can however track the default route to decrement the priority BUT I will have a IBGP default route as well so no good.

I have been messing with tracking threshold metric - so:

I added a route-map to the neighbour setting the metric of the EBGP default route to 20.

I added the track and changed the default threshold bu the track still fails!

please see below:

track 280 ip route 0.0.0.0 0.0.0.0 metric threshold

threshold metric up 50

Gateway of last resort is 10.10.1.4 to network 0.0.0.0

     10.0.0.0/24 is subnetted, 1 subnets
C       10.10.1.0 is directly connected, FastEthernet0/0
C    192.168.1.0/24 is directly connected, FastEthernet1/0
B*   0.0.0.0/0 [20/20] via 10.10.1.4, 00:20:11

Track 280

IP route 0.0.0.0 0.0.0.0 metric threshold

Metric threshold is Down (BGP/20/255)

1 change, last change 00:46:26

Metric threshold down 255 up 50

First-hop interface is FastEthernet0/0

Can anyone tell me why the track is down????

smitesh kharecha · ‎12-04-2011

Hi,

If you are running IBGP between your routers, I suppose changing the local pref is good option.

Regards,

Smitesh

danabersoch · ‎12-05-2011

Hi Smitesh,

Thanks for the reply.

What I am looking for is something to track to then decrement the HSRP priority.

If I track the default route the track will not fail because when the default route disappears from the table (because that link is down) but is then replaced by a IBGP default route.

I need to track something that is specific to that primary link being up, like a specific route (including next hop) or what I am trying at the monent is adding a metric to the incoming route and trying to track threshold metric but that is not working (as above).

Thanks again for your reply.

Dan

Kishore Chennupati · ‎12-05-2011

Hi Dan,

Track 280

IP route 0.0.0.0 0.0.0.0 metric threshold

Metric threshold is Down (BGP/20/255)

1 change, last change 00:46:26

Metric threshold down 255 up 50

First-hop interface is FastEthernet0/0

Can anyone tell me why the track is down????

I belive the metric threshold up 50 is actually greater than the scaled metric which is 20. What happens if you lower the value from 50 to 15. so configure metric threshold up 15 and then see the state of the track object

HTH

Kishore

danabersoch · ‎12-05-2011

Kishore,

Cheers for the reply:

track 280 ip route 0.0.0.0 0.0.0.0 metric threshold

threshold metric up 20

Gateway of last resort is 10.10.1.4 to network 0.0.0.0

10.0.0.0/24 is subnetted, 1 subnets

C 10.10.1.0 is directly connected, FastEthernet0/0

C 192.168.1.0/24 is directly connected, FastEthernet1/0

B* 0.0.0.0/0 [20/20] via 10.10.1.4, 00:02:47

Track 280

IP route 0.0.0.0 0.0.0.0 metric threshold

Metric threshold is Down (BGP/20/255)

1 change, last change 00:02:06

Metric threshold down 255 up 20

First-hop interface is FastEthernet0/0

__________________________________________________________________________________

track 280 ip route 0.0.0.0 0.0.0.0 metric threshold

threshold metric up 15

Gateway of last resort is 10.10.1.4 to network 0.0.0.0

10.0.0.0/24 is subnetted, 1 subnets

C 10.10.1.0 is directly connected, FastEthernet0/0

C 192.168.1.0/24 is directly connected, FastEthernet1/0

B* 0.0.0.0/0 [20/20] via 10.10.1.4, 00:06:27

Track 280

IP route 0.0.0.0 0.0.0.0 metric threshold

Metric threshold is Down (BGP/20/255)

1 change, last change 00:06:32

Metric threshold down 255 up 15

First-hop interface is FastEthernet0/0

I just cannot see why this wont work, maybe it is an incompatability between the track and BGP??

Thanks for the try though.

Dan

mooreg-honiton · ‎05-01-2012

Sorry if this post is a bit late but for the benefit of anybody else that finds this post, the problem is with the track resolution of BGP.

Router#sh track resolution
Route type     Metric Resolution
static         10
EIGRP       2560

OSPF       1
ISIS           10
BGP          2560

If your down metric threshold is 255 then the BGP metric will need to be 255*2560 or 652800 before it is considered down by object tracking. You can change the track resolution for BGP but the minimum value is 256 so with a down value of 255 the BGP metric will need to be 65280. If the down threshold is set to 2 then the corresponding metric values for BGP will be 5120 (2560) and 512 (256) respectively before the track threshold is reached.

I've copied some relevant lines of output from one of our routers below (3925 Version 15.0(1r)M8)

Threshold up

sh ip route vrf XXX

B* 0.0.0.0/0 [20/1] via 1.2.3.4, 00:42:26

sh track 2

Track 2

IP route 0.0.0.0 0.0.0.0 metric threshold

Metric threshold is Up (BGP/1/1)

Metric threshold down 10 up 1

Threshold down

sh ip route vrf XXX

B* 0.0.0.0/0 [200/25600] via 1.2.3.4, 00:00:13

sh track 2

Track 2

I P route 0.0.0.0 0.0.0.0 metric threshold

Metric threshold is Down (BGP/25600/10)

Metric threshold down 10 up 1

Additionally, if after using the sh track resolution command BGP doesn't appear in the list, try a "debug track" command.

If you see the error below BGP isn't supported in the track command. I had this issue in Version 12.4(15)T5, RELEASE SOFTWARE (fc4)

track_route_metric_get: Unknown protocol 8 (4)

Message was edited by: Graham Moore

rpool · ‎01-17-2013

Thanks Graham! Adding the relevant information to your post about debugging to determine if BGP was supported on my ios version allowed me to confirm my suspicions quickly.