Changing BGP ISP Preference

[Tshi M]

I currently have BGP setup with two Internet Service Providers. Both ISP currently offers 5Mb and we are preferring ISP_1 over ISP_2. We are upgrading the bandwidth on ISP_2 from 5M to 10M and would like to use ISP_2. Would changing the local-preference of ISP_2 to a higher number do the trick.

current local-preference configuration:

route-map ISP_1-Default permit 10

set local-preference 200

route-map ISP_2-Default permit 10

set local-preference 110

Proposed change

route-map ISP_1-Default permit 10

set local-preference 200

route-map ISP_2-Default permit 10

set local-preference 300

[Edison Ortiz]

Increasing the local-pref on incoming routes from ISP_2 will definitely do the trick on traffic leaving your AS.

You should also work with your ISP w/ dealing on the return traffic unless you don't care how the traffic returns to you.

Regards

Edison

[Tshi M]

Thanks much Edison. I was thinking about using as-path prepend.

router bgp 65429

no synchronization

bgp log-neighbor-changes

network 208.x.x.x

timers bgp 15 30

neighbor ISP_1 peer-group

neighbor ISP_1 remote-as 1111

neighbor ISP_1 descr BACKUP ISP

neighbor ISP_1 soft-reconfiguration inbound

neighbor ISP_1 route-map ISP_1-Default in

neighbor ISP_1 route-map Route-Out-ISP_1 out

neighbor ISP_1 filter-list 50 in

neighbor ISP_2 peer-group

neighbor ISP_2 remote-as 2222

neighbor ISP_2 desc PRIMARY ISP

neighbor ISP_2 soft-reconfiguration inbound

neighbor ISP_2 route-map ISP_2-Default in

neighbor ISP_2 route-map Route-Out-ISP_2 out

neighbor ISP_2 filter-list 51 in

neighbor 206.x.x.x peer-group ISP_2

neighbor 208.x.x.81 peer-group ISP_1

neighbor 208.x.x.82 peer-group ISP_1

maximum-paths 2

no auto-summary

route-map ISP_2-out permit 10

set metric 20

!

route-map ISP_1-Default permit 10

set local-preference 200

!

route-map ISP_1-out permit 10

set metric 10

!

route-map ISP_2-Default permit 10

set local-preference 300

!

route-map Route-Out permit 10

match ip address prefix-list LIST_Out

!

route-map Route-Out-ISP_1 permit 10

match ip address prefix-list LIST_Out

!

route-map Route-Out-ISP_2 permit 10

match ip address prefix-list LIST_out

!

route-map Route-Out-ISP_1 permit 20

set as-path prepend 65429 65429 65429

[Edison Ortiz]

Prepending will work as long as the ISP allows for preprending. That's the reason I suggest to work with them on the most optimal design.

Regards

Edison.

[Tshi M]

Will I have to contact both service providers or just the one that I'd like to use as a primary?

thanks again

[Edison Ortiz]

Contact the ISP you are going to send the prepend AS to see if they allow that in their policy.

__

Edison.

[CriscoSystems]

I don't get it - if Etienne's preference is simply for his enterprise's network to use ISP_2 instead of ISP_1; and the route-maps are set up for this preference, what needs to be arranged on the ISP's side? I mean there isn't really a risk of ISP_2 returning traffic to Etienne via ISP_1...

...is there?

[Tshi M]

As it turned out, I made the changes last night and didn't have to call the service providers. So far so good.

Thanks,