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Community Member

Filter bgp default route generated by 'default-originate' command

I have a question on BGP. I have a router speaking BGP to multiple neighbors. It is generating a default route using 'default-originate' command to all of its neighbors. I would like to have some neighbors stop receiving this default route. How can I filter this default route on a particular neighbor.

5 REPLIES
Community Member

Re: Filter bgp default route generated by 'default-originate' co

use neighbor x.x.x.x default-originate instead under router bgp.

Community Member

Re: Filter bgp default route generated by 'default-originate' co

The task I would like to do is to remove the all 0.0.0.0 entries learned from BGP on this particular router:

Router A#sh ip bgp

BGP table version is 14, local router ID is 2.2.2.1

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

* 0.0.0.0 5.5.5.1 0 6533 6511 6511 i

*> 5.5.5.1 0 0 6511 6511 i

r 1.1.1.0/24 5.5.5.1 0 6533 6511 i

r> 5.5.5.1 0 0 6511 i

r 1.1.2.0/24 5.5.5.1 0 6533 6511 i

r> 5.5.5.1 0 0 6511 i

*> 2.2.1.0/24 0.0.0.0 0 32768 i

*> 2.2.2.0/24 0.0.0.0 0 32768 i

*> 10.10.1.0/24 5.5.5.3 0 0 6533 i

* 5.5.5.3 0 6511 6533 i

*> 10.10.2.0/24 5.5.5.3 0 0 6533 i

* 5.5.5.3 0 6511 6533 i

r 30.30.2.0/24 5.5.5.1 0 6533 6511 i

r> 5.5.5.1 156160 0 6511 i

*> 70.70.70.0/24 5.5.5.3 25753600 0 6533 i

* 5.5.5.3 0 6511 6533 i

*> 222.222.222.0 5.5.5.3 0 0 6533 i

Router A#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route

Gateway of last resort is 5.5.5.1 to network 0.0.0.0

200.200.200.0/30 is subnetted, 1 subnets

C 200.200.200.0 is directly connected, Serial0/0/1:0

B 222.222.222.0/24 [100/0] via 5.5.5.3, 00:05:57

C 211.211.211.0/24 is directly connected, GigabitEthernet0/1

1.0.0.0/24 is subnetted, 2 subnets

D 1.1.1.0 [90/156160] via 211.211.211.1, 03:37:37, GigabitEthernet0/1

D 1.1.2.0 [90/156160] via 211.211.211.1, 03:37:37, GigabitEthernet0/1

D EX 222.222.100.0/24

[170/30720] via 211.211.211.4, 01:49:46, GigabitEthernet0/1

2.0.0.0/24 is subnetted, 2 subnets

C 2.2.1.0 is directly connected, Loopback0

C 2.2.2.0 is directly connected, Loopback1

100.0.0.0/30 is subnetted, 1 subnets

C 100.100.100.0 is directly connected, Serial0/0/0:0

70.0.0.0/24 is subnetted, 1 subnets

B 70.70.70.0 [100/25753600] via 5.5.5.3, 00:05:59

80.0.0.0/24 is subnetted, 2 subnets

D 80.80.1.0 [90/156160] via 211.211.211.4, 03:37:40, GigabitEthernet0/1

D 80.80.2.0 [90/156160] via 211.211.211.4, 03:37:40, GigabitEthernet0/1

5.0.0.0/24 is subnetted, 1 subnets

C 5.5.5.0 is directly connected, GigabitEthernet0/0

111.0.0.0/30 is subnetted, 1 subnets

D 111.111.111.0

[90/2181120] via 211.211.211.3, 03:36:22, GigabitEthernet0/1

[90/2181120] via 211.211.211.1, 03:36:22, GigabitEthernet0/1

10.0.0.0/24 is subnetted, 2 subnets

B 10.10.1.0 [100/0] via 5.5.5.3, 00:05:59

B 10.10.2.0 [100/0] via 5.5.5.3, 00:05:59

30.0.0.0/24 is subnetted, 2 subnets

D 30.30.1.0 [90/156160] via 211.211.211.3, 03:36:24, GigabitEthernet0/1

D 30.30.2.0 [90/156160] via 211.211.211.3, 03:36:24, GigabitEthernet0/1

B* 0.0.0.0/0 [100/0] via 5.5.5.1, 00:06:00

Alameda#

Silver

Re: Filter bgp default route generated by 'default-originate' co

create a filter list:

Something like this should work.

router bgp ASN

neighbor x.x.x.x route-map IN in

!

ip prefix-list IN seq 5 deny 0.0.0.0/0

!

route-map IN permit 10

match ip address prefix-list IN

Hall of Fame Super Silver

Re: Filter bgp default route generated by 'default-originate' co

Hello Rick,

good idea I would refine it in this way:

ip prefix-list def_route seq 5 permit 0.0.0.0/0

route-map IN deny 10

match ip address prefix-list def_route

+

route-map IN permit 20

to allow all other prefixes learned from the neighbor without the second clause all prefixes are denied.

Hope to help

Giuseppe

Community Member

Re: Filter bgp default route generated by 'default-originate' co

Your solution is great. It works for me.

I was running into the problem that you described. Without the second clause on the route-map, all prefixes will be denied.

Thank you all.

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