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Load Balance Incoming BGP Traffic

This is a bit of a high-level question I'm asking, but I can provide more data if needed.

I currently have two upstream providers. One 10Gig circuit with provider A, and another 10Gig circuit with provider B. Last week we turned-up a second 10Gig circuit with provider A.

The problem I'm having is that provider A is sending 95% of traffic over the original circuit, and the new circuit barely has any traffic on it. Again, I'm referencing incoming traffic from provider A to us. Our outbound traffic to upstream is going out fine over both provider A circuits. We checked our BGP attributes to see if there might be any preferences on our end that would indicate a preferred incoming route but we found no such thing.

We opened a ticket with provider A to see if they had any attributes on their end or any BGP configuration that would send all traffic over one circuit and they said their BGP ribs closely matched. They suggested we enable BGP maximum-paths and multihop on both our circuits to resolve the issue.

I believe what they are proposing will only impact outbound traffic since that's all I can really control. Shouldn't maximum-paths (or other configuration for that matter) be enabled on their end so that they route traffic to us over both our circuits?

Any insight will be helpful.

Thanks.

2 Replies 2

Kallol Bosu
Cisco Employee
Cisco Employee

Hello,

I am not an expert in BGP but it seems you are right, multi-path allows the router to load balance at egress. 

Coming to your actual problem, 95% traffic that you are talking about (Fro Provider network to your network) , are they destined to single subnet or multiple LAN subnets ? 

If multiple, then provider should be able to use route-map/local preference/AS path at their end to manipulate the BGP metric for subnets on two different circuits to do a load balancing (say, traffic for one subnet on circuit X and other on circuit Y) . Alternatively you can use MED/AS Path to advertise the LAN subnets with different metric on two different circuits and influence your provider to send traffic destined for different subnets on two different circuits. 

Regards,

Kallol

Hi;

As per my knowledge BGP is not a routing protocol we use for traffic load balancing while BGP makes routing decisions based on paths, network policies, or rule-sets configured by administrator.

With reference to your problem will not fix via maximum-path & mulithop as recommend by your ISP.

The region I belong to, here all the Service provide strip off (or make it default) BGP attribute, you can also verified at your end.

To fix the issue I will go with Kallol Bosu, you need to make a network policy & play with BGP attributes like AS-path, MED, local preference via Route-map. Just take example you have 2 links (link-1 & link-2) with 2 network (net-a & net-b)

Link-1 prefers net-a for incoming & outgoing traffic:

Incoming: Create route-map & select net-a traffic and play with the BGP attribute MED to force ISP that traffic for net-a will use link-1 & incase of failure link-2 will be used.

Outgoing: Create route-map & select net-a traffic and play with the BGP attribute local-preference to force that my outgoing traffic for net-a will use link-1 & incase of failure link-2 will be used.

I will apply the same policy for net-b that it will use link-2 for both incoming & outgoing traffic.

 

Thanks & Best regards;

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