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Additional bgp route

Dear all,

I am doing some bgp lab practise, once i finished the bgp configuaration on one router, observe there is one additional bgp route appear in the routing table. Could you give some idea why that happened? Thank you.

Vail#sh ip ro

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 not set

B [20/2195456] via, 00:08:46 is subnetted, 1 subnets

C is directly connected, Loopback0 is variably subnetted, 4 subnets, 2 masks

B [20/2169856] via, 00:08:46

C is directly connected, Serial1/1.2 <<<<<(Why have this route)

B [20/0] via, 00:08:46

C is directly connected, Serial1/1.1

B [20/0] via, 00:08:46


Vail#sh ip int brief

Interface IP-Address OK? Method Status Protocol

Serial1/0 unassigned YES TFTP up down

Serial1/0.1 unassigned YES NVRAM up down

Serial1/0.2 unassigned YES NVRAM deleted down

Serial1/1 unassigned YES TFTP up up

Serial1/1.1 YES manual up up

Serial1/1.2 YES manual up up <<<<<<<<<<<<<<<<

Serial1/2 unassigned YES NVRAM administratively down down

Serial1/3 unassigned YES NVRAM administratively down down

Loopback0 YES manual up up


Vail#sh ip b

BGP table version is 7, local router ID is

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

*> 2169856 0 200 ?

*> 0 0 200 ?

r> 0 0 200 ? <<<<<<<<<<<<<

*> 0 0 200 ?

*> 2195456 0 200 ?


Vail#sh run int s1/1.2

Building configuration...

Current configuration : 121 bytes


interface Serial1/1.2 point-to-point

ip address

frame-relay interface-dlci 311



Vail#sh ip b s

BGP router identifier, local AS number 100

BGP table version is 7, main routing table version 7

5 network entries using 585 bytes of memory

5 path entries using 260 bytes of memory

4/3 BGP path/bestpath attribute entries using 496 bytes of memory

1 BGP AS-PATH entries using 24 bytes of memory

0 BGP route-map cache entries using 0 bytes of memory

0 BGP filter-list cache entries using 0 bytes of memory

BGP using 1365 total bytes of memory

BGP activity 11/6 prefixes, 11/6 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 4 100 42 50 7 0 0 00:10:05 0 4 200 90 82 7 0 0 00:10:05 5 <<<<<<<<<<<<<<<<<<



Re: Additional bgp route

Does your EBGP neighbor ( have a statement like network mask 'Cos that is where it is coming from to get into the BGP table. We need to see the configuration of the AS 200 neighbor.

However, it is not the BGP route that is getting into your forwarding table. That is getting overwritten with the directly connected route at AD=0.

Kevin Dorrell


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