Load Balancing Between 2 Different MPLS Carriers

[jpl861]

Hi there,

We are looking at implementing load balancing between 2 different MPLS carriers for all of our centers globally. In the U.S. there's no problem as we are all connected to the same AS for MPLS1 and MPLS2. However, in APAC, EMEA, LATAMS regions, MPLS1 carrier used different AS#. So let's say for example from APAC going to US, we'll have 3 AS count to US DC for MPLS1 and just 2 for MPLS2. So all traffic will go over MPLS2.

MPLS2 is nice because it used the same AS# across all regions.

We are doing iBGP between our edge routers so it will always pick the shortest AS count. We are thinking of doing inbound AS-Path prepend for MPLS2 to match the AS-Path count of MPLS1 for regions affected.

Another option I have in mind is to ignore the AS-Path length and instead use origin attribute so we can get away from the AS-Path count but that's going to be a lot of work.

Are there other methods?

Edit: I am not really looking to load balance the traffic like 50/50. As long as the L3 switches would see both paths as the same then I am good.

Thanks!

[Predrag Jovic]

Generally, if possible, you can use summarization. Longest match is always preferred. Simple example there are 4 networks:

192.168.0/24 - link A
192.168.1/24 - link A
192.168.2/24 - link B
192.168.3/24 - link B

To send traffic for 192.168.0/24 and 192.168.1/24 through link A we can summarize and advertise all networks to 192.168.0/22 and advertise non summarized routes 192.168.0/24 and 192.168.1/24 (or 192.168.0/23 only on link A. For link B we can do the same - advertise 192.168.0/22 and advertise non summarized routes 192.168.2/24 and 192.168.3/24 (or 192.168.2/23) only through link B. Range 192.168.0/22 is advertised on both links for failover in the case one link is lost. Any variation of scenario if possible.

Longer prefix will be preferred to reach destination: load balance and failover: full address range is still advertised on both links.

[jpl861]

Thanks man. Yeah looks like that's going to be our option. I was just wondering if someone has ever tried to do load-balancing using other methods. We have bunch of data center routes that's why it unbalanced network advertisement isn't my first option.

Thanks for the input.