Thursday, February 18, 2021

BGP advertising network that should be blocked

I have a switch - My router - ISP router

My router is running eigrp with the switch - and redistributing eigrp routes into bgp for the ISP peer router at 169.x.x. 25

The problem is BGP is advertising the route 10.195.92 / 22 that is receives from eigrp - when it should only be advertising 10.195.92 / 23.

The easy fix here would be to only advertise 10.195.92 / 23 via eigrp from switch to my router.

However I'm convinced the route map eigrp2bgp config below should only advertise to my isp router 169.x.x. 25 the route 10.195.92 / 23

Partial config below from MyRouter

MyRouter#show ip bgp neighbors 169.x.x.25 advertised-routes

Network Next Hop Metric LocPrf Weight Path

*> 10.195.92.0/23 10.195.84.515 32768 ?

*> 10.195.92.0/22 10.195.84.515 32768 ?

MyRouter#sh ip bgp route-map eigrp2bgp

Network Next Hop Metric LocPrf Weight Path

*> 10.195.92.0/23 10.195.84.515 32768 ?

*> 10.195.92.0/22 10.195.84.515 32768 ?

MyRouter#sh run | sec bgp

router bgp 65500

bgp log-neighbor-changes

neighbor 169.x.x.25 remote-as 5466

redistribute connected metric 1

redistribute static metric 1 route-map cpe-static

redistribute eigrp 200 metric 5 route-map eigrp2bgp

neighbor 169.x.x.25 activate

neighbor 169.x.x25 route-map BGP-FILTER-IN in

maximum-paths 4

exit-address-family

!

address-family nsap

maximum-paths 4

exit-address-family

route-map eigrp2bgp permit 10

match ip address 99

MyRouter#show route-map eigrp2bgp

route-map eigrp2bgp, permit, sequence 10

Match clauses:

ip address (access-lists): 99

Set clauses:

Policy routing matches: 0 packets, 0 bytes

MyRouter#sh access-list 99

Standard IP access list 99

10 permit 10.195.99.48

20 permit 10.195.99.72

30 permit 10.195.99.73

40 permit 10.195.92.0, wildcard bits 0.0.1.255 (24 matches)

50 permit 10.195.84.56, wildcard bits 0.0.0.7 (12 matches)

60 permit 10.195.84.88, wildcard bits 0.0.0.7 (12 matches)

Any advice much appreciated.



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