Conditional BGP advertisement on ASR9K (Version 6.2.3)

[farrych]

Hi,

I need help for below scenario.

I have two ISPs (ISP1 & ISP2) connections with my Router, first one is 2x10G and second is 40G link.

Currently links (2x10G) with ISP1 carrying around 15G traffic with load sharing over eBGP over loopback address (with next two hops by configuring two static routes for that loopback).

Until here everything is fine, the problem is if one of two 10G links goes down with ISP1 then extra traffic ( above than 10G) would drop since remaining 10G link can handle only 10G maximum.

So is there any solution to have some kind conditional advertisement that once any of 10G link goes down, half of subnets advertised to ISP1 withdrawn (let's say 5 out of 10) and advertised to ISP2 (40G link) and remaining 5 subnets are still advertised on remaining UP 10G?

The purpose is to use 2x10G links maximum while keeping 40G as backup if any of 10G link goes down.

Thanks

[cofee]

Hi,

In my opinion conditional advertisement using advertise maps wouldn't work in your set up, especially with 2 seperate active active links going to isp 1.

An eem script can work by tracking static routes or physical interfaces, and if any of the 2 interfaces goes down, eem script will trigger to remove any 5 networks that are being advertised to isp 1 and move it to isp 2.

There might be an easier way of fixing this, but I can't think of it. 

[farrych]

Hi,
Thanks for feedback, actually for ISP2 I can advertise subnets as supernet so it will handle traffic once most specific subnets removed from ISP1.
I cannot think further how to achieve target solution.

[cofee]

You mean without using the eem script? because without it that would only work when both your 10gig uplinks are down.

[farrych]

Actually I cannot use eem script as it would need special approvals etc. and I don’t want to put in such things.
I want to have another solution considering my target.

[cofee]

I understand if you don't want to use an eem script as it can make things complicated. I thought you said that you have another way of making this work with just one 10 gig connection being up and I was interested in knowing your solution.

[farrych]

Hi All,

Please help if anyone know right solution other than EMM.

Regards,