BGP to EIGRP redistribution and filtering

[gizbri]

I am on the customer side of BGP with my carrier

Looking for the best way to filter the carriers networks(our BGP interfaces and neighbors) from being redistributed from BGP to EIGRP

Thanks

[smehrnia]

Hi there,

route-maps and prefix lists.

HTH,
Soroush.

[gizbri]

Soroush - thanks for the reply. I was hoping for a little more info. Anyone have an example or link explaining this a little more?

[smehrnia]

you can control what routes be redistributed into your EIGRP instance from BGP, with route-maps.

you select the routes you want or you dont want to be redistributed with prefix-lists, then using route-maps you call those prefix-lists and Allow or deny them. then you apply the route-map while configuring the redistribution.

example, if i dont want network 172.16.55.0/24 and 192.10.1.100/26 to be redistributed into my EIGRP:

ip prefix-list EIGRP permit 172.16.55.0/24

ip prefix-list EIGRP permit 192.10.1.0/26

route-map BGP_EIGRP deny 10

match ip address prefix-list EIGRP

route-map BGP_EIGRP permit 20

router eigrp 100

redistribute bgp 20 route-map BGP_EIGRP metric xxxx

Also keep in mind to setup appropriate metric for the routes comming from BGP.

useful link: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009487e.shtml#ex2

if you had further questions plz ask

plz Rate if it helped,

Soroush.

[gizbri]

Soroush - thanks for the explanation. A few questions. on the prefix-list its permit and it gets denied on the route map, is that correct ? Also, is route-map BGP_EIGRP permit 20 to permit all other routes ?

Thanks

[smehrnia]

yes, for this task you permit network perfixes (based on ur decision) and the prefix-list gets denied in the route-map, then the route-map is assigned to the redistribution process.

route-maps (like access-lists) have an implicit deny at the end. so whenever u r using route-maps to filter routes, you have to have this in mind.

however, if you want to let a few subnets to be redistributed in the EIGRP, i suggest u do the opposite, permit the ones u want and deny all other.

HTH,

plz Rate if it helped.

Soroush.

[gizbri]

but in this case route-map BGP_EIGRP permit 20 allows everything else ??

[smehrnia]

yes it allowes everything else.

Soroush.

[gizbri]

Ok - thanks for the info