Load sharing/balancing between 2 Service Providers

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Sep 1st, 2008
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Hi,

I have a scenario where I have the following and this is repeated at different sites globally.


CE1-----------PE1_SP1---MPLS cloud

|

CE1---standby--PE2_SP1---MPLS cloud



CE2-----------PE1_SP2----MPLS Cloud

|

CE2---standby--PE2_SP2---MPLS Cloud


2 different service providers and we require load sharing/balancing to both SP1 and SP2.


If either of the SP's PE router is down it should bring up the standby link.


2 ASN, not sure if I can load share different prefixes in this scenario.


Will the applications fail?


Will the traffic flow be symmetric ?



Any help is very much appreciated.


Thanks,

Paul

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Giuseppe Larosa Mon, 09/01/2008 - 12:22
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Hello Paul,

if you are using a single CE router on each site.


to get load-balancing on your CEx:


router bgp X

maximum-paths 2


eBGP load-balancing is easier so 2 ISP ASN is fine


Verify that you have flow based load-balancing and everything should be fine.


Notice that you have a failure on site N of provider1 you can be able to detect it in all remote sites only if they are receiving the routes of all the sites. If receiving a default route there's no way for other sites to detect the failure.

If receiving all the prefixes after MP-BGP convergence in ISP1 site N's prefixes will be withdrawn and will be reachable only via ISP2.


To use an active/standby


on all Cex


router bgp x

neighbor PE-ISP1 weigth 500

neighbor PE-ISP1 fast-external-fallover


in this way until a prefix is present in ISP1 MP-BGP traffic is sent via ISP1


If using two CE in each site things are a little more complex and you need an iBGP session between them.




Hope to help

Giuseppe


PAUL CHEN Mon, 09/01/2008 - 15:37
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Hi Giuseppe,


Thanks for the help. We may have 2 CEs in each site for each provider. So there are actually 4 CEs at each site.


Load balancing is between the 2 different providers.


So, I need to a ibgp peering session between the 2 CEs, please show me what else needs to be configured.


CE1 ---active--- PE_SP1

|

CE2 ---active--- PE_SP2


The standby links of each provider will back up their own active links, as shown in my earlier diagram


Thanks again,

Paul

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