BGP load balancing Issue

[Vinayaka Raman]

Please go through the attached doc and suggest the needful.

[dc-csa-blr]

Dear Raman,

Did you configure  "maximum-paths 2 " command under BGP ??

and for inbound traffic you must use MED for IBGP and As-path Prepending for eBGP.

If possible to send ur current config.

HTH

[Marwan ALshawi]

Each ISP uses something called bgp community string that can effect the route path and selection within the ISP cloud

Contact each ISP to see what you can send them to let each ISP prefer the advertised route within it's AS over the other ISP

In the case the mpls DC and remote sites will route over the mpls

I Am assuming remote sties are not multi homed to both ISPs

HTH

[shehinpm1]

for the outbound driection u can use local preference for certain subnets.or u can ask u r IPS to configure MED

as out direction to u r one of the CE router.

if possible post u r current route-map config

[Vinayaka Raman]

1. I have attached the configs of CR1 and CR2..
2. maximum-paths 2 is not configured..
3. Remote sites are not multi-homed

[Marwan ALshawi]

Please be aware what you asked for is how remote sites access the dc which means you got nothing to do with maximum path this command you use if you multiple bgp peers on the same router over multiple links

Your case two different routers and ISPs

What I mentioned above one way to do it

Good luck

[shehinpm1]

Hi raman,

try to do this, edit u r ip prefix-list "blocked-sites" and add some remote sites subnets with most prefer sequence number.

and in u r blocked-sites site route map set LP as 200 and re-apply this route map IN bound direction in CR2.

BR,

shehin.

[Vinayaka Raman]

Shehin,

Should CR1 and CR2 be  iBGP neighbhors for this to take effect ?

[Marwan ALshawi]

Dear Shehin

What you have mentioned will effect how the dc router cr1 or cr2 chose the path but first he has to influence the remote sites how they can reach the cr sites using local ISP of each one this need to be aligned with ISP policies as the routing can be changed within the ISP cloud it self

[Vinayaka Raman]

Can I configure a higher MED on CR1 out so that remote sites will start using CR2 ?

If yes, I wanted only specifc remote sites to prefer CR1.

Is there a change required from ISP end ?

[Marwan ALshawi]

Ok this better diagram

First of all when you want to influence the bgp path you need to think about how the traffic will go out over which path and howbthe traffic will returne over which path

In your case I am assuming you want remote sites connected to AS 4809 to use cr2 as the primary

While remote sites connected to AS 65500 to use cr1 as primary

Let put is into to direction

First from the cr to remote sites

To let each cr to prefer the path for specific remote sites over the directly connected BGP AS then create prefix list that contain all the networks of those remote sites then match in a route map and in this route map increase the local preference and then apply it in the inbound direction do this on each of the cr routers with prefix list as each one need to prefer different networks

Now you have the preference on each cr router for outbound direction done but your LAN is using EIGRP so the local r preference not effect the other router and I am assuming there might be devices in the LAN using/peering over eigrp to get what you have done in bgp reflected into eigrp   Use in each of the cr routers the same prefix list put it in a new route map first sequence match this prefix list and put a low route metrec and second sequence just make it permit to match anything else and put higher metric use this route map when you redistribute bgp into eigrp

Second

From remote sites to the cr routers direction

I do not recommend you to med as it might have unexpected result not mention most ISPs do not accept it so you need to check with your ISP

But think about bit this way each remote site has one link to the ISP and the ISPs they are linked between them so once the remote site send traffic tonthe ISP it is up to the ISP how to route the traffic you can not effect both ISPs for certain remote sites selectively you need it to get done within the ISP cloud

Just contact each ISP and find out what community string they to make the route with higher local preference in their AS

And in this way you advertise the /20 in each cr using the community of each ISP tagged with the route and you makensure now remote sites will use then directly connected ISP as the primary up to the respective cr

I know it is not that easy but once you understand the logic you will be fine

Hop this help

[shehinpm1]

Hi marvan,

yes, the method which i suggested the raffic from DC to out.better to check with u r ISP before doing,bcoz as marvan

mentioned some ISPs will not allow to tune the traffic with some attributes.