[isp-bgp] Re: BGP Multi-homing

[Pete Templin <petelists@...>]

Muhammad Umar Farooq wrote:

> Network Info:
> 1) One Cisco router running BGP.
> 2) Connected with two backbone providers. (A and B)
> 3) /21 IP block from APNIC.
> Requirements:
> 1) Some IP classes to use A as primary link and others to use B as
> primary link.
> 2) In case of failure of any one link all traffic redirected to the
> available link.
Get another router.  Put backbone B on the other router.  Put A-centric 
networks on one router, B-centric networks on the other router. 
Announce A-centric networks to backbone A, and to backbone B with extra 
prepends and perhaps a provider-specific community to request a lower 
local preference within their providers.  Announce B-centric networks to 
backbone B, and to backbone A with extra prepends and perhaps a 
provider-specific community to request a lower local preference within 
their providers.  Have router 1 default outbound to backbone A, and 
router 2 default outbound to backbone B.

If you want to do it on one router, you'll need to use policy routing to 
control the outbound path, which adds complexity, particularly when 
troubleshooting.

pt








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