BGP loadbalancing

NAVIN PARWAL · ‎08-05-2005

Folks,

We have a ds3 and a T1 connection to the internet. We have a class C address allocated by the ANAI.

We would like out internet traffic to use the Primary DS3 connection first and only if that fails then we would like to use out t1. Is it possible?

at the present time we are doing load balancing in which some traffic goes over 1 link and some goes over the other. We are not worried about the traffic coming inbound as we do not have any webservers.

Thanks

saimbt · ‎08-05-2005

do u learn the default route from the service provider or the entire internet routing table.

you can ask the service provider to send you only the default route and ask the second provider to send u a default route with a larger MED value or u can set a local preference to your primary provider.

-Sai.

vdadlaney · ‎08-05-2005

Hi Navin,

Are you using multiple Routers?

Are your links to the same provider or to separate providers?

Since you are not concerned with Inbound Traffic you can run IBGP between your BGP speaking routers (that is if you are using different routers ofcourse) and ask your ISPs to advertise a default route to you and set the local preference on the T1 side for routes received from that ISP lower. Than redistribute the default. That would be one way. Haven't tried it myself. Please correct me if i have missed something or am incorrect. Thx

v_milenko · ‎08-09-2005

First variant: You have connection with single ISP.

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You can configure BGP with your ISP or use default routes.If you choose BGP, you can use private AS number.You can announce either your PI addresses or PA addresses to ISP. Learn default route or full internet route table from ISP.

For DS3 link selection you can use LOCAL_PREF (outbound traffic) and MED (inbound traffic).

Second variant: You have connection with different ISPs.

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This is difficult case. You MUST obtain own public AS number. You MUST configure BGP with ISPs. You MUST announce your PI addresses to ISPs. Learn default route or full internet route table from ISPs.

For DS3 link selection you can use LOCAL_PREF (outbound traffic) and AS_PATH prepend (inbound traffic). Be carefull, don't make you AS transit.

Good luck.