Subject: eBGP out-bound load sharing with 2 Different Service provider

From: Abhishek Mittal <[email-masked]>
Date: Fri, 19 Dec 2003 20:38:02 -0800 (PST)

Hi ,
 
I have one query regarding BGP out-bond load sharing.
 
I have two different upstream ISP from where we have taken the Internet bandwidth.
 
From one service provider (ABC) we have 3 eBGP sessions for 3 different links.
One is for Premium bandwidth  second is for shared bandwidth and third is for Interconnect of that service provider used as multihoming , as we have the same service provider in other locations also.
We are receiving default route as well as local peering route from fist & second eBGP peering and only default route from third eBGP peering respectively.
 
From second service provider (XYZ) we have only one eBGP peeing. and we are receiving only default routes as well as local -peering routes.
 
Now First service provider (ABC) is exporting the BGP communities to upstream provider.For all the 3 eBGP sessions are having different communities.That's why it will take the different path.
 
Now we want to send the outbound traffic of some prefixes from ABC's first link and rest traffic from (XYZ).As well as we want to make the redundancy for both.
 
1> We are using the distribution lists only not prefix list in BGP policies. 
2> We are using ip default-network not 0/0 route.There for both the ISP are having different default-network.
3> IP default-network is same for all 3 links of first (ABC) ISP.
4> In bond traffic is managing properly as we are announcing aggregate on all the eBGP sessions as well as different prefixes on different eBGP sessions as per our requirement.And we are having the full redundancy for in bond traffic.As we are using high prepend for some eBGP peering.
5> All eBGP peering is made with loopback ip .
6> We are using serial link for connectivity with service provider.
7> We are using OSPF as IGP and BGP as EGP.
8> We can not have full routing table due to router restriction.We have Cisco 7513 for this. 
 
Problem :
 
If we sharing the out bond traffic on first service provider (ABC) on first and second link, (ABC) is exporting the community and set the different community.So both will take the different uplink path and second one is not having any redundancy after (ABC) gateway (As per SLA). So it could create a problem like.....one packet will go and another packet will drop.
 
Therefore to avoid this problem we want to send our out-bond traffic for some prefixes on (ABC) first link and rest on (XYZ). And want to build redundancy also.We don't want to use (ABC)'s third link because it is commissioned for different purpose.
 
Kindly give us some guidelines , how can we make this scenario to serve better for our customer.Might be there is some thing missing, if so kindly let me  know ......
 
I 'll highly appreciate your kind response for the same.
 
Thanks & Regards
Abhishek Mittal

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