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Community Member

Route reflectors and load balancing..

We have an issue ( which we solved with a fix for the moment being ), whereas we have two route reflectors. The two remote PE routers are dual homed with load balancing in place. The customer VRF are connected to both PE's with Ethernet..

The issue is with RR's, that they only import one route ( the best according to RR's selection mechanisms ).

What this means is, that both RR's will get ( if bandwith is the same and so on ), the same next hop, which makes the load-balancing fail. Traffic will only use one link, because there is the same next-hop

What we did to fix this behaviour is to have different cost to the RR's from the different PE's point of view. One RR is closer in ospf cost from one of the PE's and the other way around.

Is there any other possible solution, maybe a new BGP implementation where you can force the RR's to import two routes with similar cost ??

/ BR Daniel

4 REPLIES
Cisco Employee

Re: Route reflectors and load balancing..

I have come across the same issue a couple of years ago. One way to achieve load-balancing in this scenario is to assign different route distinguishers (RD) to the same VRF on different PE. This way the RR sees the VPNv4 as being different and won't try to slelect one of the two.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Cisco Employee

Re: Route reflectors and load balancing..

Sorry, Typing too fast. The last sentence should be: This way the RR sees the two VPNv4 routes as being different and will forward them both to the other PE therefore allowing load-balancing.

Hope it's better now ;o)

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Community Member

Re: Route reflectors and load balancing..

Hi,

Thank's for the reply. And the answer is yes - absolutely - this is something you can do for a vpn that is connected to both remote PE routers. But..if you have another scenario, where you have one VRF ( say a serial link, into one of the PE's ), it won't be load balanced, there is only one RD for this.. but.. i guess - it's nothing much you can do about that ..

Cisco Employee

Re: Route reflectors and load balancing..

I'm not sure I understand your last scenario. You mean one CE connected via multiple links to the same PE? If both connections are to the same PE then you will be able to load balance on the PE-CE links.

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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