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New Member

BGP advertisement issue: Cannot advertise one particular route

Can anyone help me out with my BGP advertisement issue?

I used to be connected with an upstream provider who has given me a /24 to use in my network. Now that our company has just been granted with our own address space by a regional NIC, we decided to migrate our point-to-point connection into BGP-4 peering.

We managed to advertise our own address space but not the upstream-provided /24. Issuing the "sho ip bgp nei <peer-address> advertised-routes" only returns our own address space yet we are very sure that similar configurations were set for each of the blocks. Any idea what could be preventing us to advertise our upstream-provided block?

Our upstream assured us that they have not set any filter that would block the cited address block.

Would there be any conflict if we are both advertising the same block? They could still be announcing the same block as a part of a major net. Do I have to ask them to remove the particular block from their advertisement? Also, I haven't created a route object for this block yet, do you think it has any effect?

Anyone's input will be highly appreciated. Many thanks in advance.

5 REPLIES
New Member

Re: BGP advertisement issue: Cannot advertise one particular rou

Can you post your BGP configuration and also a 'sh ip route ' that matches

both the networks you are trying to advertise? Also post the 'sh ip bgp neighbor adv'

for the EBGP neighbor? They key should be that you have an exact route in the routing table

that matches what you have the network statement configured for under BGP.

New Member

Re: BGP advertisement issue: Cannot advertise one particular rou

Many thanks for the reply. Below are the BGP config lines in my router. Please pardon me for removing all IP information for confidentiality reasons.

Note that I still have a default static-route. This is because the networks x.x.x.0/24, x.x.y.0/24, and x.x.z.0/24 are currently being routed back to us statically. These are the same networks that we wish to announce via BGP but with which we are having trouble advertising. We are currently testing only the block x.x.x.0/24. We will remove the default-route as soon as we are able to advertise them to our upstream.

router bgp 1234

no synchronization

bgp log-neighbor-changes

bgp dampening

network x.x.x.0

network x.x.y.0

network x.x.z.0

network A.A.A.0

network A.A.B.0

network A.A.C.0

network A.A.D.0

network A.A.E.0

network A.A.F.0

network A.A.G.0

network A.A.H.0

network A.A.I.0

network A.A.J.0

network A.A.K.0

network A.A.L.0

network A.A.M.0

network A.A.N.0

network A.A.O.0

network A.A.P.0

neighbor w.w.w.1 remote-as 4321

neighbor w.w.w.1 version 4

neighbor w.w.w.1 soft-reconfiguration inbound

neighbor w.w.w.1 prefix-list FILTER in

neighbor w.w.w.1 filter-list 10 out

no auto-summary

!

ip classless

ip route 0.0.0.0 0.0.0.0 w.w.w.1

ip route x.x.x.0 255.255.255.0 Null0 250

ip route x.x.y.0 255.255.255.0 Null0 250

ip route x.x.z.0 255.255.255.0 Null0 250

ip route A.A.A.0 255.255.255.0 Null0 250

ip route A.A.B.0 255.255.255.0 Null0 250

ip route A.A.C.0 255.255.255.0 Null0 250

ip route A.A.D.0 255.255.255.0 Null0 250

ip route A.A.E.0 255.255.255.0 Null0 250

ip route A.A.F.0 255.255.255.0 Null0 250

ip route A.A.G.0 255.255.255.0 Null0 250

ip route A.A.H.0 255.255.255.0 Null0 250

ip route A.A.I.0 255.255.255.0 Null0 250

ip route A.A.J.0 255.255.255.0 Null0 250

ip route A.A.K.0 255.255.255.0 Null0 250

ip route A.A.L.0 255.255.255.0 Null0 250

ip route A.A.M.0 255.255.255.0 Null0 250

ip route A.A.N.0 255.255.255.0 Null0 250

ip route A.A.O.0 255.255.255.0 Null0 250

ip route A.A.P.0 255.255.255.0 Null0 250

ip as-path access-list 10 permit ^$

!

!

ip prefix-list FILTER seq 5 deny 10.0.0.0/8 le 32

ip prefix-list FILTER seq 10 deny 127.0.0.0/8 le 32

ip prefix-list FILTER seq 15 deny 169.254.0.0/16 le 32

ip prefix-list FILTER seq 20 deny 172.16.0.0/12 le 32

ip prefix-list FILTER seq 25 deny 192.0.2.0/24 le 32

ip prefix-list FILTER seq 30 deny 192.168.0.0/16 le 32

ip prefix-list FILTER seq 35 deny 224.0.0.0/3 le 32

ip prefix-list FILTER seq 40 permit 0.0.0.0/0 le 32

Router#sho ip bgp neigh w.w.w.1 advertised-routes

BGP table version is 515030, local router ID is A.A.A.32

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*> A.A.A.0 0.0.0.0 0 32768 i

*> A.A.B.0 0.0.0.0 0 32768 i

*> A.A.C.0 0.0.0.0 0 32768 i

*> A.A.D.0 0.0.0.0 0 32768 i

*> A.A.E.0 0.0.0.0 0 32768 i

*> A.A.F.0 0.0.0.0 0 32768 i

*> A.A.G.0 0.0.0.0 0 32768 i

*> A.A.H.0 0.0.0.0 0 32768 i

*> A.A.I.0 0.0.0.0 0 32768 i

*> A.A.J.0 0.0.0.0 0 32768 i

*> A.A.K.0 0.0.0.0 0 32768 i

*> A.A.L.0 0.0.0.0 0 32768 i

*> A.A.M.0 0.0.0.0 0 32768 i

*> A.A.N.0 0.0.0.0 0 32768 i

*> A.A.O.0 0.0.0.0 0 32768 i

*> A.A.P.0 0.0.0.0 0 32768 i

Router#sho ip route | begi x.x.x.0

O E2 x.x.x.0/24 [110/20] via A.A.A.14, 00:39:51, GigabitEthernet0/0

Appreciate your comments and suggestions.

New Member

Re: BGP advertisement issue: Cannot advertise one particular rou

Have you done the BGP session reset?

New Member

Re: BGP advertisement issue: Cannot advertise one particular rou

Thanks for the reply. Yes, I've done it a several times. Please correct me if I'm wrong, but isn't it that I should still be able to at least see the missing advertisements using the "sho ip bgp neigh advertised-routes" command even if a filter could be existing on the remote router?

Rgds,

RICO

New Member

Re: BGP advertisement issue: Cannot advertise one particular rou

You are correct, All of the advertising network should be seen by "show ip bgp neigh w.w.w.1 ad". I suggest you try the "neighbor w.w.w.1 distribute-list XX out" command.

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