multipath does not to reach a destination

LincolnR · ‎06-24-2020

Hello.

I am in need of help.

I have a topology that I intend to create failover from R1 to R4. When dropping from R1 # ping 4.4.4.4 so loo0 the packet leaves via R3. I need R1 packets to go out through R2 if R3 fails. I configured maximum paths on R1 but it didn't work.

R1 (config) #router bgp 500
R1 (config-router) # maximum-paths 2

**************************

R1

ospf router 1
!
bgp 500 router
bgp log-neighbor-changes
network 1.1.1.1 mask 255.255.255.255
neighbor 192.168.12.2 remote-as 500
neighbor 192.168.13.3 remote-as 500

*************************************

R2

ospf router 1
!
bgp 500 router
bgp router-id 22.2.2.2
bgp log-neighbor-changes
network 2.2.2.2 mask 255.255.255.255
neighbor 192.168.12.1 remote-as 500
neighbor 192.168.12.1 next-hop-self
neighbor 192.168.23.3 remote-as 500
neighbor 192.168.23.3 next-hop-self
neighbor 200.1.27.7 remote-as 65000
neighbor 200.1.27.7 allowas-in

*******************************

R3

ospf router 1
!
bgp 500 router
bgp log-neighbor-changes
network 3.3.3.3 mask 255.255.255.255
neighbor 192.168.13.1 remote-as 500
neighbor 192.168.13.1 next-hop-self
neighbor 192.168.23.2 remote-as 500
neighbor 192.168.23.2 next-hop-self
neighbor 200.1.38.8 remote-as 65000
neighbor 200.1.38.8 allowas-in
!

********************************************

R8

vrf definition BLUE
rd 1: 1
!
address-family ipv4
route-target export 500: 500
route-target import 500: 500
exit-address-family

!

ospf router 1
mpls ldp autoconfig
router-id 8.8.8.8
!
bgp 65000 router
bgp log-neighbor-changes
no bgp default ipv4-unicast
neighbor 9.9.9.9 remote-as 65000
neighbor 9.9.9.9 update-source Loopback0
neighbor 10.10.10.10 remote-as 65000
neighbor 10.10.10.10 update-source Loopback0
!
address-family ipv4
exit-address-family
!
address-family vpnv4
neighbor 9.9.9.9 activate
neighbor 9.9.9.9 send-community extended
neighbor 10.10.10.10 activate
neighbor 10.10.10.10 send-community extended
exit-address-family
!
address-family ipv4 vrf BLUE
neighbor 200.1.38.3 remote-as 500
neighbor 200.1.38.3 activate
exit-address-family

*************************************

R7

vrf definition BLUE
rd 1: 1
!
address-family ipv4
route-target export 500: 500
route-target import 500: 500
exit-address-family

!

ospf router 1
mpls ldp autoconfig
router-id 7.7.7.7
!
bgp 65000 router
bgp log-neighbor-changes
no bgp default ipv4-unicast
neighbor 9.9.9.9 remote-as 65000
neighbor 9.9.9.9 update-source Loopback0
neighbor 10.10.10.10 remote-as 65000
neighbor 10.10.10.10 update-source Loopback0
!
address-family ipv4
exit-address-family
!
address-family vpnv4
neighbor 9.9.9.9 activate
neighbor 9.9.9.9 send-community extended
neighbor 10.10.10.10 activate
neighbor 10.10.10.10 send-community extended
exit-address-family
!
address-family ipv4 vrf BLUE
neighbor 200.1.27.2 remote-as 500
neighbor 200.1.27.2 activate
exit-address-family

Giuseppe Larosa · ‎06-25-2020

Hello @LincolnR ,

post

on R1:

show ip bgp 4.4.4.4

show ip route 4.4.4.4

check the same on R2 and R3 and verifiy if you have an iBGP session between R2 and R3. This last one if present can lead one of routers R2,R3 to prefer the route received from the other for any reason and this will lead to a single path available on R1.

In short you likely need the same command for multipath also on R2,R3.

Hope to help

Giuseppe

LincolnR · ‎06-25-2020

Giuseppe

There is IBGP session between in the routers R2 and R3. I need to do that if interface G0/0 on R3 (R3-->R1) goes down the packets switchover to R2 until R4.

The topology attached

R1#show ip bgp 4.4.4.4
BGP routing table entry for 4.4.4.4/32, version 5
Paths: (2 available, best #2, table default)
Not advertised to any peer
65000 500
192.168.12.2 from 192.168.12.2 (22.2.2.2)
Origin IGP, metric 0, localpref 100, valid, internal
65000 500
192.168.13.3 from 192.168.13.3 (3.3.3.3)
Origin IGP, metric 0, localpref 100, valid, internal, best
R1#ping 4.4.4.4 so loo0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 104/165/312 ms
R1#trace
R1#traceroute 4.4.4.4 sou
R1#traceroute 4.4.4.4 source loo0
Type escape sequence to abort.
Tracing the route to 4.4.4.4
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.13.3 96 msec 16 msec 12 msec
2 200.1.38.8 60 msec 36 msec 28 msec
3 10.1.108.10 [MPLS: Labels 24/28 Exp 0] 92 msec 84 msec 56 msec
4 200.1.126.12 [MPLS: Label 28 Exp 0] 96 msec 52 msec 60 msec
5 200.1.126.6 84 msec 76 msec 100 msec
6 192.168.46.4 108 msec 140 msec 72 msec
R1#

R1#show ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 500", distance 200, metric 0
Tag 65000, type internal
Last update from 192.168.13.3 00:27:19 ago
Routing Descriptor Blocks:
* 192.168.13.3, from 192.168.13.3, 00:27:19 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 65000
MPLS label: none

R2#sh ip bgp 4.4.4.4
BGP routing table entry for 4.4.4.4/32, version 7
Paths: (2 available, best #1, table default)
Advertised to update-groups:
1
65000 500
200.1.27.7 from 200.1.27.7 (7.7.7.7)
Origin IGP, localpref 100, valid, external, best
65000 500
192.168.23.3 from 192.168.23.3 (3.3.3.3)
Origin IGP, metric 0, localpref 100, valid, internal
R2#sh ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 500", distance 20, metric 0
Tag 65000, type external
Last update from 200.1.27.7 00:46:05 ago
Routing Descriptor Blocks:
* 200.1.27.7, from 200.1.27.7, 00:46:05 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 65000
MPLS label: none
R2#
R3#sh ip bgp 4.4.4.4
BGP routing table entry for 4.4.4.4/32, version 5
Paths: (2 available, best #2, table default)
Advertised to update-groups:
1
65000 500
192.168.23.2 from 192.168.23.2 (22.2.2.2)
Origin IGP, metric 0, localpref 100, valid, internal
65000 500
200.1.38.8 from 200.1.38.8 (8.8.8.8)
Origin IGP, localpref 100, valid, external, best
R3#sh ip rou
R3#sh ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 500", distance 20, metric 0
Tag 65000, type external
Last update from 200.1.38.8 00:45:18 ago
Routing Descriptor Blocks:
* 200.1.38.8, from 200.1.38.8, 00:45:18 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 65000
MPLS label: none
R3#

Giuseppe Larosa · ‎06-26-2020

Hello @LincolnR ,

your configuration looks like fine but from the point of view of Router R1 it is comparing two iBGP advertisements.

Try to see if after maximum-paths you have an ibgp option

something like

maximum-paths ibgp 2

Hope to help

Giuseppe

LincolnR · ‎06-26-2020

hello Giuseppe.

I asked for help here. Because I used the "maximum-paths ibgp 2" configuration and the package did not arrive at R4. So I removed the configuration and asked for help here. I reconfigured R1 with "maximum-paths ibgp 2"
and it worked. There is no explanation. Maybe it's a bug in GNS3.

Thanks very much.