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BGP Load balancing & Multihoming

Hi

I would like to do a BGP multihoming with our service providers for our internet connection

and will to advertise the following networks 213.13.222.0/27 and 213.13.222.32/27 to both ISP

I want to distribute my traffic to both the ISP without getting the entire routing table from the ISPs

The internet browsing traffic needs to be forwarded to ISP B and the other static NAts to be forwarded to ISPA with each ISP acting as fallback to each other. THis will be achieved by policy routing wherein the browsing traffic will natted from the range 213.13.222.0/27 and the others will be natted from the range 213.13.222.32/27.

Now heres what i feel i would have problem

Can i have specific attributes applied to only a set of routes advertised to one BGP neighbor. Heres the config i plan

Router bgp 31380

Network 213.13.222.0 mask 255.255.255.227

Network 213.13.222.32 mask 255.255.255.227

Neighbor 111.111.111.111 remote-as 200

Neighbor 111.111.111.111 route-map ISPA-local-routes out

Neighbor 111.111.111.111 route-map Acceptroutes in

Neighbor 123.123.123.123 remote-as 300

Neighbor 123.123.123.123 route-map ISPB-local-routes out

Neighbor 123.123.123.123 prefix-list Acceptroutes in

access-list 1 permit 213.13.222.32 0.0.0.31

access-list 2 permit 213.13.222.0 0.0.0.31

access-list 3 permit 0.0.0.0

ip prefix-list? Acceptroutes seq 5 permit 0.0.0.0/0

Route-map ISPA-local-routes permit 10

Match ip address 1

Set as-path prepend 31380 31380 31380 31380 31380

Route-map ISPA-local-routes permit 20

Match ip address 2

Route-map ISPB-local-routes permit 10

Match ip address 2

Set as-path prepend 31380 31380 31380 31380 31380

Route-map ISPB-local-routes permit 20

Match ip address 1

Set as-path prepend 31380 31380 31380 31380 31380

route-map browsing-traffic permit 10

match ip address 1

set ip next-hop 111.111.111.111

interface fastethernet 0/1

ip address 159.145.145.1

ip policy route-map browsing-traffic

Will the above config work for my scenario. Also i need to know whether the return trafiic for browsing will be from ISPB and not from ISPA

Thanks in Advance

Narayan

1 REPLY
Gold

Re: BGP Load balancing & Multihoming

Your configuration will mostly do what you want and I assume you have looked at the NAT failover stuff if you want your nat to work transparently. The as prepend only works to a point. There may be cases where this path is shorter even with all the perpends. No way to tell but this is still the best way to try to accomplish want you want.

Now the bad news.

No ISP will let you advertise a /27 network. They almost always set a /24 as the longest mask. If the addresses you posted are valid these are owned by

Telepac - Comunicacoes Interactivas, SA

A second ISP will not advertise another ISP's addresses. You will need your own block of addresses and a AS number.

To do what you want you will actually need 2 /24 blocks so that you can use one in each ISP as the preferred route.

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