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LAN Interface down - down - Subnets still advertised in BGP

thomas.fayet
Level 1
Level 1

Hello,

Here is my router configuration :

router bgp 65000

bgp log-neighbor-changes

no synchronisation

  no auto-summary

network 10.0.0.0 mask 255.252.0.0

network 10.49.0.0 mask 255.255.0.0

network 10.100.0.0 mask 255.252.0.0

network 10.104.0.0 mask 255.252.0.0

neighbor x.x.x.x remote-as xxxx

!

ip route 10.0.0.0 255.252.0.0 10.210.0.4

ip route 10.49.0.0 255.255.0.0 10.210.0.4

ip route 10.100.0.0 255.252.0.0 10.210.0.4

ip route 10.104.0.0 255.252.0.0 10.210.0.4

My router  LAN interface is down/down , the host 10.210.0.4 is cascaded behind the lan .

GigabitEthernet0/0         10.210.0.1      YES manual down                  down   

But still the router advertised all the route into BGP to his neighbor . I am pretty that before the 15.x mainline , the behavior was different and routes were not installed in the routing table while the interface was physically and logically down or when the ip next hop was unreacheable .

The router is a 1941 using  15(4)M1 .

Could someone explain if this a normal behavior or if I am missing somehting here .

Rgds

Da

5 Replies 5

hello Thomas,

Once the interface is down , are you abele to see the static routes on routing table then you are probably hitting CSCtk12608

bug.

Hope this helps

Harish

Hello .

Nope , LAN interface are down down and routes are not in the routing table at this time .

Now I am also talking OSPF with the client so I am also getting the route from OSPF into the routing table .

I am just thinking of removing the static routes completely , but still I want to know if I am facing here a normal behavior or a bug .

Does the network statement in BGP would "force" the router to advertise the routes , even when the lan interface o the next hop attached to the static route is down ?

was#sh ip route

Codes: L - local, 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, H - NHRP, l - LISP

       + - replicated route, % - next hop override

Gateway of last resort is not set

      57.0.0.0/8 is variably subnetted, 6 subnets, 4 masks

S        57.7.0.0/16 is directly connected, Null0

S        57.7.0.0/17 [30/0] via 57.213.172.221

C        57.213.172.220/30 is directly connected, Serial0/0/0.101

L        57.213.172.222/32 is directly connected, Serial0/0/0.101

C        57.214.91.32/32 is directly connected, Loopback1111

C        57.238.78.152/32 is directly connected, Loopback79

pwas455#

GigabitEthernet0/0         10.210.0.1      YES manual down                  down   

Hello Thomas,

>> Does the network statement in BGP would "force" the router to advertise the routes , even when the lan interface o the next hop attached to the static route is down ?

No, it shouldn't behave this way.

with the GE interface down can you post

show ip bgp 10.0.0.0

show ip bgp 10.49.0.0

show ip bgp 10100.0.0

show ip bgp 10.104.0.0

Hope to help

Giuseppe

Jigar Dave
Level 3
Level 3

1. can you provide - "Show ip bgp summary" result

2. can you provide - "show ip route " output before and after the change

3. make sure that you have not "redestribute static" command in your bgp config.

Thanks,

JD...

Hi

There is no redistribute static in bgp .

I will do a testing with the client to grap the infos above and let you know

thanks

Rgds

T

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