BGP Mulisite Multihoming

rbermel83 · ‎07-29-2009

I am trying to setup a Multisite Multihoming WAN configuration between two sites and three ISP's. I have two routers at site A both on different ISP's and a single router at site B on another ISP. I am able to control traffic at site A using a combination of local preference and AS prepending to send traffic to the router of my chosing. I have a similar configuration setup at site B also with local preference AS prepending, however the I cannot get the traffic to cooperate. Here is the current BGP configuration at site B.

router bgp as_number

no synchronization

no bgp enforce-first-as

bgp log-neighbor-changes

network x.x.x.x mask 255.255.255.0

network y.y.y.y mask 255.255.255.0

neighbor z.z.z.z remote-as 32007

neighbor z.z.z.z ebgp-multihop 255

neighbor z.z.z.z send-community

neighbor z.z.z.z.z route-map as out

neighbor z.z.z.z.z remote-as remote_as

no auto-summary

route-map as permit 10

match as-path 10

set as-path prepend as_number as_number as_number as_number as_number

set community remote_as:80

Any help is greatly appreciated

Istvan_Rabai · ‎07-29-2009

Hi Ryan,

If you have one connection to one ISP at site B, then I don't quite get what traffic characteristic you would like to influence.

Can you please clarify?

Thanks:

Istvan

rbermel83 · ‎07-30-2009

What I am attempting to accomplish with this is the ability to be able to announce the prefix that I am currently using at Site A with Site B so that if I am unable to reach Site A for whatever reason the Prefix will fail over to Site B.

I have narrowed the issue down to the fact that despite the fact that I have configured the prefix at site A to be announced at site B it is actually not being announced due to the non-existence of the route in the routing table. I have tried to add an ip route x.x.x.x 255.255.255.0 null0 200 route but that seems to send all traffic destined for the x.x.x.x network to a black hole.

Any input is greatly appreciated.

Thank you

Rick Morris · ‎07-30-2009

This may be long but I need to understand.

Site A - Primary

Site B - Back-up

Site A announce 10.1.1.0/24

Site B announce 10.1.1.0/24 higher meds

I understand the IP's are not specific for you, it helps me see it.

From your routers have you verified the BGP announcements?

sh ip bgp neigh adv

Have you gone to a looking glass to see the routes?

sh ip bgp

sh ip bgp 10.1.1.0

Can you post the config for both sites?

router bgp

routes

route maps

prefix-lists

Also a sh ip bgp neigh adv

You can replace public IP's with private, it would help.

rbermel83 · ‎07-30-2009

here are the scrubbed bgp configurations from the routers:

Site A Router 1

router bgp 1

no synchronization

bgp log-neighbor-changes

network 10.1.1.0 mask 255.255.255.0

neighbor 172.16.0.209 remote-as 2828

neighbor 172.16.0.209 ebgp-multihop 255

neighbor 172.16.0.209 send-community

neighbor 172.16.0.209 route-map AS-1_out out

no auto-summary

route-map AS-1_out permit 10

set community 2828:1512

Site A Router 2

router bgp 1

no synchronization

bgp log-neighbor-changes

network 10.1.1.0 mask 255.255.255.0

neighbor 192.16.2.237 remote-as 174

neighbor 192.16.2.237 ebgp-multihop 255

neighbor 192.16.2.237 send-community

neighbor 192.16.2.237 route-map PREPEND out

no auto-summary

route-map PREPEND permit 10

set as-path prepend 1 1 1 1

set community 174:70

Site B Router 1

router bgp 1

no synchronization

no bgp enforce-first-as

bgp log-neighbor-changes

network 10.1.1.0 mask 255.255.255.0

network 10.2.1.0 mask 255.255.255.0

neighbor 206.223.138.126 remote-as 2

neighbor 206.223.138.126 send-community

neighbor 206.223.138.126 route-map AS1 out

neighbor 206.223.138.254 remote-as 2

neighbor 206.223.138.254 send-community

neighbor 206.223.138.254 route-map AS14739 out

no auto-summary

route-map AS1 permit 10

match as-path 10

set as-path prepend 1 1 1 1 1

set community 2:80

BGP table version is 6722447, local router ID is 206.223.138.192

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*> 10.2.1.0.0/24 0.0.0.0 0 32768 i