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received bgp route seen in "sh ip bgp" but not in "sh ip route" and not re-announced

iosonoumberto
Level 1
Level 1

Hello,

I have this bgo config

 

!
bgp multiple-instance
!
router bgp 65501
max-paths ebgp 2
redistribute kernel
neighbor 192.168.88.1 remote-as 64520
neighbor 192.168.88.1 ebgp-multihop 255
neighbor 192.168.88.1 soft-reconfiguration inbound
neighbor 192.168.88.1 prefix-list epg-in in
neighbor 192.168.88.1 prefix-list epg-out out
neighbor 192.168.88.1 as-override
neighbor 192.168.99.1 remote-as 64520
neighbor 192.168.99.1 ebgp-multihop 255
neighbor 192.168.99.1 soft-reconfiguration inbound
neighbor 192.168.99.1 prefix-list web-in in
neighbor 192.168.99.1 prefix-list web-out out
neighbor 192.168.99.1 as-override
!

 

In ingress direction I correctly filter only the routes I need

 

VPX-LB-01#sh ip bgp neighbors 192.168.88.1 routes
Node Id: 0
BGP table version is 9, local router ID is 192.168.99.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, l - labeled
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
* 10.10.0.0/24 0.0.0.0 0 0 64520 65504 ?

Total number of prefixes 1
VPX-LB-01#sh ip bgp neighbors 192.168.99.1 routes
Node Id: 0
BGP table version is 9, local router ID is 192.168.99.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, l - labeled
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
* 0.0.0.0/0 0.0.0.0 0 0 64520 65505 i

Total number of prefixes 1

 

I see the routes in the bgp db:

 

VPX-LB-01#sh ip bgp
Node Id: 0
BGP table version is 10, local router ID is 192.168.99.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, l - labeled
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
* 0.0.0.0/0 0.0.0.0 0 0 64520 65505 i
* 10.10.0.0/24 0.0.0.0 0 0 64520 65504 ?

 

I read online that next-hop 0.0.0.0 means "locally generated route" but that is not the case :) i would expect the neighbor, being ebgp, to be neighbor address (192.168.88.1 or 99.1)

 

the routes are not in the routing table

 

VPX-LB-01#sh ip route bgp
Node Id: 0

Gateway of last resort is not set
VPX-LB-01#

 

export policies are matching the right routes

 

VPX-LB-01#sh ip bgp prefix-list epg-out
Node Id: 0
BGP table version is 11, local router ID is 192.168.99.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, l - labeled
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
* 0.0.0.0/0 0.0.0.0 0 0 64520 65505 i

Total number of prefixes 1
VPX-LB-01#sh ip bgp prefix-list web-out
Node Id: 0
BGP table version is 11, local router ID is 192.168.99.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, l - labeled
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
* 10.10.0.0/24 0.0.0.0 0 0 64520 65504 ?

 

but nothing is announced:

 

VPX-LB-01#sh ip bgp neighbors | include announced
0 announced prefixes
0 announced prefixes

 

can anyone help me understand what I am missing?

 

thanks in advance for the help

Umberto

 

 

 

8 Replies 8

Harold Ritter
Cisco Employee
Cisco Employee

The fact that the routes are not installed in the RIB is likely due to the fact that the next hop 0.0.0.0 is considered unreachable. The next hop is sent as part of the BGP update.  You seem to be running Quagga. Are neighbors 192.168.88.1 and 192.168.99.1 Quagga as well? Is it possible that they set the next hop to 0.0.0.0?

 

Could you please provide a "show ip bgp 10.0.0.0/24"?

 

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

VM is a citrix netscaler

BGP neighbor is Juniper Contrail

 

here is my output

 

VPX-LB-01#sh ip bgp 10.10.0.0/24
Node Id: 0
BGP routing table entry for 10.10.0.0/24
Paths: (1 available, no best path)
Not advertised to any peer
64520 65504
0.0.0.0 (inaccessible) from 192.168.88.1 (192.168.200.10)
Origin incomplete metric 0, localpref 100, valid, external
Last update: Wed May 8 09:34:57 2019

 

2 issues

- no best path

- inaccessible nh (0.0.0.0)

 

so according to this it is correct not to see the bgp route

 

I captured packets on the citrix VM port inorder to lacate BGP update messages

 

bgp_upd_nh.png

As you can see the next-hop is set correctly to 192.168.88.1 so it seems that somehow the VM ignored that value

Hello,

 

on a side note, I tried to recreate this in GNS3 with only Cisco routers, it seems to work as designed. I understand that you are using virtual routers, so maybe that is the problem...

what kind of problem do you think might be related to using VMs?

 

the BGP update has the correct next-hop

but inside next-hop scaler that is overridden by 0.0.0.0

 

ping to 192.168.88.1 is working fine

> 2 issues

> - no best path

> - inaccessible nh (0.0.0.0)

 

In fact, it is only one issue. The "no best path" condition is actually due to the next hop being unreachable.

 

The Citrix NetScaler seems to be resetting the next hop for some reason. You should probably check with your Citrix support team why that might be.

 

I am not sure it is related, but is there any reason you configured "neighbor 192.168.88.1 ebgp-multihop 255"? It it not needed if the neighbor is directly connected.

 

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

yeah,

i agree we need support from citrix

by the way, ebgp multihop is needed in order to establish session with contrail vrouter

I just noticed that you have next hop address within the MP_REACH_NLRI. Could you please expand this field so that we can see what it contains?

 

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

rishrapsody1
Level 1
Level 1

Only best routes are advertised to neighbor's over Bgp.

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