topic Re: BGP reachability issue from different AS in Routing and SD-WAN

BGP reachability issue from different AS

R Manjunatha — Wed, 14 Sep 2022 06:15:13 GMT

Unable to ping from one AS 65001 i.e R61 to another AS 65002 R54, R53 and R58.similarly AS65003 R59, R50 and R55.but am getting all the BGP routes. I configured next hop self towards ebgp routers as well.

ex- from R61 unable to ping IP add 192.54.10.1 and 192.55.10.1

 R61

interface Loopback0
ip address 61.61.61.61 255.255.255.0
!
interface Loopback1
ip address 192.61.10.1 255.255.255.0
!
interface Loopback2
ip address 192.61.20.2 255.255.255.0
!
interface Loopback3
ip address 192.61.30.3 255.255.255.0
!
interface Loopback4
ip address 192.61.40.4 255.255.255.0
!
interface Ethernet0/0
ip address 10.10.61.2 255.255.255.0
duplex auto
!
interface Ethernet0/1
no ip address
duplex auto
!
interface Ethernet0/2
ip address 172.16.85.2 255.255.255.0
duplex auto
!
interface Ethernet0/3
no ip address
shutdown
duplex auto
!
interface Ethernet1/0
no ip address
shutdown
duplex auto
!
interface Ethernet1/1
no ip address
shutdown
duplex auto
!
interface Ethernet1/2
no ip address
shutdown
duplex auto
!
interface Ethernet1/3
no ip address
shutdown
duplex auto
!
!
router eigrp 100
network 172.16.85.0 0.0.0.255
!
router ospf 1
router-id 61.61.61.61
network 10.10.48.0 0.0.0.255 area 0
network 10.10.61.0 0.0.0.255 area 0
network 61.61.61.0 0.0.0.255 area 0
!
router bgp 65002
bgp log-neighbor-changes
network 61.61.61.0 mask 255.255.255.0
network 172.16.85.0 mask 255.255.255.0
network 192.61.10.0
network 192.61.20.0
network 192.61.30.0
network 192.61.40.0
neighbor 48.48.48.48 remote-as 65002
neighbor 48.48.48.48 update-source Loopback0
neighbor 48.48.48.48 next-hop-self
neighbor 52.52.52.52 remote-as 65002
neighbor 52.52.52.52 update-source Loopback0
neighbor 52.52.52.52 next-hop-self
neighbor 60.60.60.60 remote-as 65002
neighbor 60.60.60.60 update-source Loopback0
neighbor 60.60.60.60 next-hop-self

R61(config-router)# DO SH IP BGP
BGP table version is 68, local router ID is 192.61.40.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
x best-external, a additional-path, c RIB-compressed,
t secondary path,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path
*>i 10.10.49.0/24 48.48.48.48 0 100 0 65001 i
*>i 10.10.54.0/24 48.48.48.48 0 100 0 65001 i
*>i 48.48.48.0/24 48.48.48.48 0 100 0 i
*>i 49.49.49.0/24 48.48.48.48 0 100 0 65001 i
*> 61.61.61.0/24 0.0.0.0 0 32768 i
*>i 172.16.1.0/24 52.52.52.52 0 100 0 i
*>i 172.16.2.0/24 48.48.48.48 0 100 0 i
*>i 172.16.3.0/24 52.52.52.52 0 100 0 65003 i
*> 172.16.85.0/24 0.0.0.0 0 32768 i
*>i 192.48.10.0 48.48.48.48 0 100 0 i
*>i 192.48.20.0 48.48.48.48 0 100 0 i
*>i 192.48.30.0 48.48.48.48 0 100 0 i
*>i 192.48.40.0 48.48.48.48 0 100 0 i
Network Next Hop Metric LocPrf Weight Path
*>i 192.49.10.0 48.48.48.48 0 100 0 65001 i
*>i 192.49.20.0 48.48.48.48 0 100 0 65001 i
*>i 192.49.30.0 48.48.48.48 0 100 0 65001 i
*>i 192.49.40.0 48.48.48.48 0 100 0 65001 i
*>i 192.50.10.0 52.52.52.52 0 100 0 65003 i
*>i 192.50.20.0 52.52.52.52 0 100 0 65003 i
*>i 192.50.30.0 52.52.52.52 0 100 0 65003 i
*>i 192.50.40.0 52.52.52.52 0 100 0 65003 i
*>i 192.52.10.0 52.52.52.52 0 100 0 i
*>i 192.52.20.0 52.52.52.52 0 100 0 i
*>i 192.52.30.0 52.52.52.52 0 100 0 i
*>i 192.52.40.0 52.52.52.52 0 100 0 i
*>i 192.53.10.0 52.52.52.52 0 100 0 65003 65001 i
*>i 192.53.20.0 52.52.52.52 0 100 0 65003 65001 i
*>i 192.53.30.0 52.52.52.52 0 100 0 65003 65001 i
*>i 192.53.40.0 52.52.52.52 0 100 0 65003 65001 i
*>i 192.54.10.0 48.48.48.48 0 100 0 65001 i
*>i 192.54.20.0 48.48.48.48 0 100 0 65001 i
*>i 192.54.30.0 48.48.48.48 0 100 0 65001 i
*>i 192.54.40.0 48.48.48.48 0 100 0 65001 i
*>i 192.55.10.0 52.52.52.52 0 100 0 65003 i
*>i 192.55.20.0 52.52.52.52 0 100 0 65003 i
Network Next Hop Metric LocPrf Weight Path
*>i 192.55.30.0 52.52.52.52 0 100 0 65003 i
*>i 192.55.40.0 52.52.52.52 0 100 0 65003 i
*>i 192.56.10.0 52.52.52.52 0 100 0 65003 i
*>i 192.56.20.0 52.52.52.52 0 100 0 65003 i
*>i 192.56.30.0 52.52.52.52 0 100 0 65003 i
*>i 192.56.40.0 52.52.52.52 0 100 0 65003 i
*>i 192.58.10.0 48.48.48.48 0 100 0 65001 i
*>i 192.58.20.0 48.48.48.48 0 100 0 65001 i
*>i 192.58.30.0 48.48.48.48 0 100 0 65001 i
*>i 192.58.40.0 48.48.48.48 0 100 0 65001 i
*>i 192.59.10.0 52.52.52.52 0 100 0 65003 i
*>i 192.59.20.0 52.52.52.52 0 100 0 65003 i
*>i 192.59.30.0 52.52.52.52 0 100 0 65003 i
*>i 192.59.40.0 52.52.52.52 0 100 0 65003 i
*>i 192.60.10.0 60.60.60.60 0 100 0 i
*>i 192.60.20.0 60.60.60.60 0 100 0 i
*>i 192.60.30.0 60.60.60.60 0 100 0 i
*>i 192.60.40.0 60.60.60.60 0 100 0 i
*> 192.61.10.0 0.0.0.0 0 32768 i
*> 192.61.20.0 0.0.0.0 0 32768 i
*> 192.61.30.0 0.0.0.0 0 32768 i
*> 192.61.40.0 0.0.0.0 0 32768 i
Network Next Hop Metric LocPrf Weight Path
*>i 192.168.50.0 60.60.60.60 0 100 0 i
R61(config-router)#

R61(config-router)#DO sh ip rou bgp
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
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 7 subnets, 2 masks
B 10.10.49.0/24 [200/0] via 48.48.48.48, 00:53:58
B 10.10.54.0/24 [200/0] via 48.48.48.48, 00:53:38
48.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
B 48.48.48.0/24 [200/0] via 48.48.48.48, 00:05:29
49.0.0.0/24 is subnetted, 1 subnets
B 49.49.49.0 [200/0] via 48.48.48.48, 00:03:57
172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks
B 172.16.1.0/24 [200/0] via 52.52.52.52, 00:53:58
B 172.16.2.0/24 [200/0] via 48.48.48.48, 00:53:58
B 172.16.3.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.48.10.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.48.20.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.48.30.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.48.40.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.49.10.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.49.20.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.49.30.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.49.40.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.50.10.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.50.20.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.50.30.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.50.40.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.52.10.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.52.20.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.52.30.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.52.40.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.53.10.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.53.20.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.53.30.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.53.40.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.54.10.0/24 [200/0] via 48.48.48.48, 00:53:38
B 192.54.20.0/24 [200/0] via 48.48.48.48, 00:53:38
B 192.54.30.0/24 [200/0] via 48.48.48.48, 00:53:38
B 192.54.40.0/24 [200/0] via 48.48.48.48, 00:53:38
B 192.55.10.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.55.20.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.55.30.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.55.40.0/24 [200/0] via 52.52.52.52, 00:53:45
B 192.56.10.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.56.20.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.56.30.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.56.40.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.58.10.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.58.20.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.58.30.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.58.40.0/24 [200/0] via 48.48.48.48, 00:53:58
B 192.59.10.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.59.20.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.59.30.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.59.40.0/24 [200/0] via 52.52.52.52, 00:53:58
B 192.60.10.0/24 [200/0] via 60.60.60.60, 00:53:58
B 192.60.20.0/24 [200/0] via 60.60.60.60, 00:53:58
B 192.60.30.0/24 [200/0] via 60.60.60.60, 00:53:58
B 192.60.40.0/24 [200/0] via 60.60.60.60, 00:53:58
B 192.168.50.0/24 [200/0] via 60.60.60.60, 00:53:58

R48

interface Loopback0
ip address 48.48.48.48 255.255.255.0
!
interface Loopback1
ip address 192.48.10.1 255.255.255.0
!
interface Loopback2
ip address 192.48.20.2 255.255.255.0
!
interface Loopback3
ip address 192.48.30.3 255.255.255.0
!
interface Loopback4
ip address 192.48.40.4 255.255.255.0
!
interface Ethernet0/0
no ip address
shutdown
duplex auto
!
interface Ethernet0/1
ip address 10.10.48.1 255.255.255.0
duplex auto
!
interface Ethernet0/2
ip address 10.10.61.1 255.255.255.0
duplex auto
!
interface Ethernet0/3
ip address 172.16.2.1 255.255.255.0
duplex auto
!
interface Ethernet1/0
no ip address
shutdown
duplex auto
!
interface Ethernet1/1
no ip address
shutdown
duplex auto
!
interface Ethernet1/2
no ip address
shutdown
duplex auto
!
interface Ethernet1/3
no ip address
shutdown
duplex auto
!
router ospf 1
router-id 48.48.48.48
network 10.10.48.0 0.0.0.255 area 0
network 10.10.61.0 0.0.0.255 area 0
network 48.48.48.0 0.0.0.255 area 0
!
router bgp 65002
bgp log-neighbor-changes
network 48.48.48.0 mask 255.255.255.0
network 172.16.2.0 mask 255.255.255.0
network 192.48.10.0
network 192.48.20.0
network 192.48.30.0
network 192.48.40.0
neighbor 52.52.52.52 remote-as 65002
neighbor 52.52.52.52 update-source Loopback0
neighbor 52.52.52.52 next-hop-self
neighbor 60.60.60.60 remote-as 65002
neighbor 60.60.60.60 update-source Loopback0
neighbor 60.60.60.60 next-hop-self
neighbor 61.61.61.61 remote-as 65002
neighbor 61.61.61.61 update-source Loopback0
neighbor 61.61.61.61 next-hop-self
neighbor 172.16.2.2 remote-as 65001

R49

interface Loopback0
ip address 49.49.49.49 255.255.255.0
!
interface Loopback1
ip address 192.49.10.1 255.255.255.0
!
interface Loopback2
ip address 192.49.20.2 255.255.255.0
!
interface Loopback3
ip address 192.49.30.3 255.255.255.0
!
interface Loopback4
ip address 192.49.40.4 255.255.255.0
!
interface Ethernet0/0
ip address 10.10.49.2 255.255.255.0
duplex auto
!
interface Ethernet0/1
ip address 10.10.58.1 255.255.255.0
duplex auto
!
interface Ethernet0/2
ip address 172.16.2.2 255.255.255.0
duplex auto
!
interface Ethernet0/3
no ip address
shutdown
duplex auto
!
interface Ethernet1/0
no ip address
shutdown
duplex auto
!
interface Ethernet1/1
no ip address
shutdown
duplex auto
!
interface Ethernet1/2
no ip address
shutdown
duplex auto
!
interface Ethernet1/3
no ip address
shutdown
duplex auto
!
router ospf 1
router-id 49.49.49.49
network 10.10.49.0 0.0.0.255 area 0
network 10.10.58.0 0.0.0.255 area 0
network 49.49.49.0 0.0.0.255 area 0
!
router bgp 65001
bgp log-neighbor-changes
network 49.49.49.0 mask 255.255.255.0
network 172.16.2.0 mask 255.255.255.0
network 192.49.10.0
network 192.49.20.0
network 192.49.30.0
network 192.49.40.0
neighbor 53.53.53.53 remote-as 65001
neighbor 53.53.53.53 update-source Loopback0
neighbor 53.53.53.53 next-hop-self
neighbor 54.54.54.54 remote-as 65001
neighbor 54.54.54.54 update-source Loopback0
neighbor 54.54.54.54 next-hop-self
neighbor 58.58.58.58 remote-as 65001
neighbor 58.58.58.58 update-source Loopback0
neighbor 58.58.58.58 next-hop-self
neighbor 172.16.2.1 remote-as 65002




R54

interface Loopback0
ip address 54.54.54.54 255.255.255.0
!
interface Loopback1
ip address 192.54.10.1 255.255.255.0
!
interface Loopback2
ip address 192.54.20.2 255.255.255.0
!
interface Loopback3
ip address 192.54.30.3 255.255.255.0
!
interface Loopback4
ip address 192.54.40.4 255.255.255.0
!
interface Ethernet0/0
ip address 10.10.54.1 255.255.255.0
duplex auto
!
interface Ethernet0/1
ip address 10.10.49.1 255.255.255.0
duplex auto
!
interface Ethernet0/2
no ip address
shutdown
duplex auto
!
interface Ethernet0/3
no ip address
shutdown
duplex auto
!
interface Ethernet1/0
no ip address
shutdown
duplex auto
!
interface Ethernet1/1
no ip address
shutdown
duplex auto
!
interface Ethernet1/2
no ip address
shutdown
duplex auto
!
interface Ethernet1/3
no ip address
shutdown
duplex auto
!
router ospf 1
router-id 54.54.54.54
network 10.10.49.0 0.0.0.255 area 0
network 10.10.54.0 0.0.0.255 area 0
network 54.54.54.0 0.0.0.255 area 0
!
router bgp 65001
bgp log-neighbor-changes
network 10.10.49.0 mask 255.255.255.0
network 10.10.54.0 mask 255.255.255.0
network 192.54.10.0
network 192.54.20.0
network 192.54.30.0
network 192.54.40.0
neighbor 49.49.49.49 remote-as 65001
neighbor 49.49.49.49 update-source Loopback0
neighbor 49.49.49.49 next-hop-self
neighbor 53.53.53.53 remote-as 65001
neighbor 53.53.53.53 update-source Loopback0
neighbor 53.53.53.53 next-hop-self
neighbor 58.58.58.58 remote-as 65001
neighbor 58.58.58.58 update-source Loopback0
neighbor 58.58.58.58 next-hop-self

R53

interface Loopback0
ip address 53.53.53.53 255.255.255.0
!
interface Loopback1
ip address 192.53.10.1 255.255.255.0
!
interface Loopback2
ip address 192.53.20.2 255.255.255.0
!
interface Loopback3
ip address 192.53.30.3 255.255.255.0
!
interface Loopback4
ip address 192.53.40.4 255.255.255.0
!
interface Ethernet0/0
ip address 10.10.54.2 255.255.255.0
duplex auto
!
interface Ethernet0/1
ip address 10.10.53.2 255.255.255.0
duplex auto
!
interface Ethernet0/2
no ip address
shutdown
duplex auto
!
interface Ethernet0/3
no ip address
shutdown
duplex auto
!
interface Ethernet1/0
no ip address
shutdown
duplex auto
!
interface Ethernet1/1
no ip address
shutdown
duplex auto
!
interface Ethernet1/2
no ip address
shutdown
duplex auto
!
interface Ethernet1/3
no ip address
shutdown
duplex auto
!
router ospf 1
router-id 53.53.53.53
network 10.10.53.0 0.0.0.255 area 0
network 10.10.54.0 0.0.0.255 area 0
network 53.53.53.0 0.0.0.255 area 0
!
router bgp 65001
bgp log-neighbor-changes
network 192.53.10.0
network 192.53.20.0
network 192.53.30.0
network 192.53.40.0
network 192.54.10.0
network 192.54.20.0
network 192.54.30.0
network 192.54.40.0
neighbor 54.54.54.54 remote-as 65001
neighbor 54.54.54.54 update-source Loopback0
neighbor 58.58.58.58 remote-as 65001
neighbor 58.58.58.58 update-source Loopback0
!

Re: BGP reachability issue from different AS

R Manjunatha — Sun, 11 Sep 2022 15:43:16 GMT

I have attached the topology for your reference

Re: BGP reachability issue from different AS

MHM Cisco World — Wed, 14 Sep 2022 08:39:40 GMT

friend
go to destination router, do

show ip route

check if the source router LO is learn
if it learn then
use


ping x.x.x.x source y.y.y.y

this is BGP not ospf or eigrp.

Re: BGP reachability issue from different AS

R Manjunatha — Wed, 14 Sep 2022 06:21:29 GMT

This is destination R53 router

show ip route

and source R53 as per the topology.

Do I need to advertise loopback 0 IP address in BGP routes in all the routers?

R53 destination

R53# 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
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
O 10.10.49.0/24 [110/20] via 10.10.54.1, 01:43:34, Ethernet0/0
C 10.10.53.0/24 is directly connected, Ethernet0/1
L 10.10.53.2/32 is directly connected, Ethernet0/1
C 10.10.54.0/24 is directly connected, Ethernet0/0
L 10.10.54.2/32 is directly connected, Ethernet0/0
O 10.10.58.0/24 [110/20] via 10.10.53.1, 01:43:24, Ethernet0/1
49.0.0.0/32 is subnetted, 1 subnets
O 49.49.49.49 [110/21] via 10.10.54.1, 01:43:24, Ethernet0/0
[110/21] via 10.10.53.1, 01:43:24, Ethernet0/1
53.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 53.53.53.0/24 is directly connected, Loopback0
L 53.53.53.53/32 is directly connected, Loopback0
54.0.0.0/32 is subnetted, 1 subnets
O 54.54.54.54 [110/11] via 10.10.54.1, 01:43:34, Ethernet0/0
58.0.0.0/32 is subnetted, 1 subnets
O 58.58.58.58 [110/11] via 10.10.53.1, 01:43:24, Ethernet0/1
172.16.0.0/24 is subnetted, 2 subnets
B 172.16.1.0 [200/0] via 58.58.58.58, 01:42:21
B 172.16.3.0 [200/0] via 58.58.58.58, 01:42:40
B 192.50.10.0/24 [200/0] via 58.58.58.58, 01:42:21
B 192.50.20.0/24 [200/0] via 58.58.58.58, 01:42:21
B 192.50.30.0/24 [200/0] via 58.58.58.58, 01:42:21
B 192.50.40.0/24 [200/0] via 58.58.58.58, 01:42:21
192.53.10.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.53.10.0/24 is directly connected, Loopback1
L 192.53.10.1/32 is directly connected, Loopback1
192.53.20.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.53.20.0/24 is directly connected, Loopback2
L 192.53.20.2/32 is directly connected, Loopback2
192.53.30.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.53.30.0/24 is directly connected, Loopback3
L 192.53.30.3/32 is directly connected, Loopback3
192.53.40.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.53.40.0/24 is directly connected, Loopback4
L 192.53.40.4/32 is directly connected, Loopback4
B 192.54.10.0/24 [200/0] via 54.54.54.54, 01:42:40
B 192.54.20.0/24 [200/0] via 54.54.54.54, 01:42:40
B 192.54.30.0/24 [200/0] via 54.54.54.54, 01:42:40
B 192.54.40.0/24 [200/0] via 54.54.54.54, 01:42:40
B 192.55.10.0/24 [200/0] via 58.58.58.58, 01:41:50
B 192.55.20.0/24 [200/0] via 58.58.58.58, 01:41:50
B 192.55.30.0/24 [200/0] via 58.58.58.58, 01:41:50
B 192.55.40.0/24 [200/0] via 58.58.58.58, 01:41:50
B 192.56.10.0/24 [200/0] via 58.58.58.58, 01:42:21
B 192.56.20.0/24 [200/0] via 58.58.58.58, 01:42:21
B 192.56.30.0/24 [200/0] via 58.58.58.58, 01:42:21
B 192.56.40.0/24 [200/0] via 58.58.58.58, 01:42:21
B 192.58.10.0/24 [200/0] via 58.58.58.58, 01:42:40
B 192.58.20.0/24 [200/0] via 58.58.58.58, 01:42:40
B 192.58.30.0/24 [200/0] via 58.58.58.58, 01:42:40
B 192.58.40.0/24 [200/0] via 58.58.58.58, 01:42:40
B 192.59.10.0/24 [200/0] via 58.58.58.58, 01:42:40
B 192.59.20.0/24 [200/0] via 58.58.58.58, 01:42:40
B 192.59.30.0/24 [200/0] via 58.58.58.58, 01:42:40
B 192.59.40.0/24 [200/0] via 58.58.58.58, 01:42:40

R61 source

R61#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
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 7 subnets, 2 masks
O 10.10.48.0/24 [110/20] via 10.10.61.1, 01:45:28, Ethernet0/0
B 10.10.49.0/24 [200/0] via 48.48.48.48, 01:44:36
O 10.10.52.0/24 [110/40] via 10.10.61.1, 01:45:18, Ethernet0/0
B 10.10.54.0/24 [200/0] via 48.48.48.48, 01:44:16
O 10.10.60.0/24 [110/30] via 10.10.61.1, 01:45:28, Ethernet0/0
C 10.10.61.0/24 is directly connected, Ethernet0/0
L 10.10.61.2/32 is directly connected, Ethernet0/0
48.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
B 48.48.48.0/24 [200/0] via 48.48.48.48, 00:56:07
O 48.48.48.48/32 [110/11] via 10.10.61.1, 01:45:48, Ethernet0/0
49.0.0.0/24 is subnetted, 1 subnets
B 49.49.49.0 [200/0] via 48.48.48.48, 00:54:35
52.0.0.0/32 is subnetted, 1 subnets
O 52.52.52.52 [110/31] via 10.10.61.1, 01:45:18, Ethernet0/0
60.0.0.0/32 is subnetted, 1 subnets
O 60.60.60.60 [110/21] via 10.10.61.1, 01:45:28, Ethernet0/0
61.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 61.61.61.0/24 is directly connected, Loopback0
L 61.61.61.61/32 is directly connected, Loopback0
172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks
B 172.16.1.0/24 [200/0] via 52.52.52.52, 01:44:36
B 172.16.2.0/24 [200/0] via 48.48.48.48, 01:44:36
B 172.16.3.0/24 [200/0] via 52.52.52.52, 01:44:36
C 172.16.85.0/24 is directly connected, Ethernet0/2
L 172.16.85.2/32 is directly connected, Ethernet0/2
B 192.48.10.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.48.20.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.48.30.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.48.40.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.49.10.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.49.20.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.49.30.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.49.40.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.50.10.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.50.20.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.50.30.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.50.40.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.52.10.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.52.20.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.52.30.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.52.40.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.53.10.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.53.20.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.53.30.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.53.40.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.54.10.0/24 [200/0] via 48.48.48.48, 01:44:16
B 192.54.20.0/24 [200/0] via 48.48.48.48, 01:44:16
B 192.54.30.0/24 [200/0] via 48.48.48.48, 01:44:16
B 192.54.40.0/24 [200/0] via 48.48.48.48, 01:44:16
B 192.55.10.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.55.20.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.55.30.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.55.40.0/24 [200/0] via 52.52.52.52, 01:44:23
B 192.56.10.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.56.20.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.56.30.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.56.40.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.58.10.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.58.20.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.58.30.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.58.40.0/24 [200/0] via 48.48.48.48, 01:44:36
B 192.59.10.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.59.20.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.59.30.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.59.40.0/24 [200/0] via 52.52.52.52, 01:44:36
B 192.60.10.0/24 [200/0] via 60.60.60.60, 01:44:36
B 192.60.20.0/24 [200/0] via 60.60.60.60, 01:44:36
B 192.60.30.0/24 [200/0] via 60.60.60.60, 01:44:36
B 192.60.40.0/24 [200/0] via 60.60.60.60, 01:44:36
192.61.10.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.61.10.0/24 is directly connected, Loopback1
L 192.61.10.1/32 is directly connected, Loopback1
192.61.20.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.61.20.0/24 is directly connected, Loopback2
L 192.61.20.2/32 is directly connected, Loopback2
192.61.30.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.61.30.0/24 is directly connected, Loopback3
L 192.61.30.3/32 is directly connected, Loopback3
192.61.40.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.61.40.0/24 is directly connected, Loopback4
L 192.61.40.4/32 is directly connected, Loopback4
B 192.168.50.0/24 [200/0] via 60.60.60.60, 01:44:36
R61#

Re: BGP reachability issue from different AS

MHM Cisco World — Sun, 11 Sep 2022 17:10:38 GMT

if the Lo only use to as BGP update source then no need
do traceroute with source and find where the packet is stop.

Re: BGP reachability issue from different AS

R Manjunatha — Wed, 14 Sep 2022 08:42:25 GMT

its taking path R60 not reaching to R49

R61#traceroute 192.53.10.1
Type escape sequence to abort.
Tracing the route to 192.53.10.1
VRF info: (vrf in name/id, vrf out name/id)
1 10.10.61.1 1 msec 1 msec 1 msec
2 10.10.48.2 1 msec 2 msec 2 msec
3 10.10.60.2 2 msec 3 msec 2 msec
4 * * *
5 * * *
6 * * *
7 *

Re: BGP reachability issue from different AS

MHM Cisco World — Sun, 11 Sep 2022 17:31:24 GMT

and that why the connection failed go to 10.10.60.2 and check the path to destination go to which router and check that router is the prefix is in RIB or not.

Re: BGP reachability issue from different AS

Harold Ritter — Wed, 14 Sep 2022 08:43:19 GMT

Hi @R Manjunatha ,

It is normal that traceroute it is not going to R49, but rather to R60, as the BGP path being learnt for 192.53.10.0/24 on R61 is via R52:

*>i 192.53.10.0 52.52.52.52 0 100 0 65003 65001 i

The reason for that is that R53 only advertises its local route to R54 and R58, which explains why the only path available in AS65002 is via AS65003. You are missing the following configuration on R53:

router bgp 65001

neighbor 49.49.49.49 remote-as 65001

neighbor 49.49.49.49 update-source Loopback0

Also, it would be a good idea to specify the source address when performing a traceroute or ping, as by default R61 will use 10.10.61.2, which is not propagated in BGP. For instance, this causes the traceroute you provided to break on R56, which has no idea how to get to 10.10.61.2. The source address you specify should be from a prefix propagated via BGP.

Regards,

Re: BGP reachability issue from different AS

Harold Ritter — Sun, 11 Sep 2022 19:07:44 GMT

Hi @MHM Cisco World ,

The traceroute breaks on R56 because the source address was not specified and R56 has not idea how to reach 10.10.61.2, which is the source address used by R61 by default.

Regards,

Re: BGP reachability issue from different AS

paul driver — Wed, 14 Sep 2022 08:45:20 GMT

Hello
looks like you have a full ibgp mesh, as such depending how old your rtr IOS is, you need to turn off synchronization and auto summarization, plus make sure you have full IGP route table for all loopbacks and physical links within the ibgp mesh.


router xxx
no auto-summary
no synchronization

Re: BGP reachability issue from different AS

R Manjunatha — Mon, 12 Sep 2022 08:58:11 GMT

Thanks, Harold

I got it. I have one question.

Is there any best practice that without using source address while ping or traceroute, if I advertise local interface

Re: BGP reachability issue from different AS

MHM Cisco World — Mon, 12 Sep 2022 09:40:09 GMT

using ping or tracroute without source can be with only one step
redistribute the prefix learn from BGP into IGP in each AS.
this make all router know all prefix.

Re: BGP reachability issue from different AS

R Manjunatha — Mon, 12 Sep 2022 11:44:43 GMT

Yes...

but I believe that is not a good idea in a production network.

Re: BGP reachability issue from different AS

MHM Cisco World — Mon, 12 Sep 2022 12:05:27 GMT

OK, I will ask you something, why we need iBGP inside AS (except iBGP of edge router interconnect )??

Re: BGP reachability issue from different AS

Harold Ritter — Mon, 12 Sep 2022 12:44:50 GMT

Hi @R Manjunatha ,

Advertising your interface addresses would not be best practice. In most real life scenario, all you need to advertise is a handful of prefixes from one AS to the other. Specifying the source address to test connectivity is very common.

Regards,

Re: BGP reachability issue from different AS

R Manjunatha — Wed, 14 Sep 2022 06:27:27 GMT

now I am clear about BGP routes ...

I need some help in redistributing BGP to eigrp , i can able to ping from R61 to eigrp routers R43, R47 and R86 similarly I could not able to ping those networks from R60, R50 and R53 different AS .

I attached topology for your reference

R61

interface Loopback0
ip address 61.61.61.61 255.255.255.0
!
interface Loopback1
ip address 192.61.10.1 255.255.255.0
!
interface Loopback2
ip address 192.61.20.2 255.255.255.0
!
interface Loopback3
ip address 192.61.30.3 255.255.255.0
!
interface Loopback4
ip address 192.61.40.4 255.255.255.0
!
interface Ethernet0/0
ip address 10.10.61.2 255.255.255.0
duplex auto
!
interface Ethernet0/1
ip address 10.10.52.1 255.255.255.0
duplex auto
!
interface Ethernet0/2
ip address 172.16.85.2 255.255.255.0
duplex auto
!
interface Ethernet0/3
no ip address
shutdown
duplex auto
!
interface Ethernet1/0
no ip address
shutdown
duplex auto
!
interface Ethernet1/1
no ip address
shutdown
duplex auto
!
interface Ethernet1/2
no ip address
shutdown
duplex auto
!
interface Ethernet1/3
no ip address
shutdown
duplex auto
!
!
router eigrp 100
network 172.16.85.0 0.0.0.255
redistribute bgp 65002 metric 10000 10 255 255 1500
!
router ospf 1
router-id 61.61.61.61
network 10.10.48.0 0.0.0.255 area 0
network 10.10.61.0 0.0.0.255 area 0
network 61.61.61.0 0.0.0.255 area 0
!
router bgp 65002
bgp log-neighbor-changes
network 61.61.61.0 mask 255.255.255.0
network 172.16.85.0 mask 255.255.255.0
network 192.61.10.0
network 192.61.20.0
network 192.61.30.0
network 192.61.40.0
redistribute eigrp 100
neighbor 48.48.48.48 remote-as 65002
neighbor 48.48.48.48 update-source Loopback0
neighbor 48.48.48.48 next-hop-self
neighbor 52.52.52.52 remote-as 65002
neighbor 52.52.52.52 update-source Loopback0
neighbor 52.52.52.52 next-hop-self
neighbor 60.60.60.60 remote-as 65002
neighbor 60.60.60.60 update-source Loopback0
neighbor 60.60.60.60 next-hop-self

R85

interface Loopback1
ip address 192.85.10.1 255.255.255.0
!
interface Loopback2
ip address 192.85.20.1 255.255.255.0
!
interface Loopback3
ip address 192.85.30.1 255.255.255.0
!
interface Loopback4
ip address 192.85.40.1 255.255.255.0
!
interface Ethernet0/0
ip address 10.10.85.2 255.255.255.0
duplex auto
!
interface Ethernet0/1
ip address 10.10.86.1 255.255.255.0
duplex auto
!
interface Ethernet0/2
ip address 10.10.10.1 255.255.255.0
duplex auto
!
interface Ethernet0/3
ip address 172.16.85.1 255.255.255.0
duplex auto
!
interface Ethernet1/0
ip address 10.10.120.1 255.255.255.0
duplex auto
!
interface Ethernet1/1
no ip address
shutdown
duplex auto
!
interface Ethernet1/2
no ip address
shutdown
duplex auto
!
interface Ethernet1/3
no ip address
shutdown
duplex auto
!
!
router eigrp 100
network 10.10.10.0 0.0.0.255
network 10.10.85.0 0.0.0.255
network 10.10.86.0 0.0.0.255
network 10.10.120.0 0.0.0.255
network 172.16.85.0 0.0.0.255
network 192.85.10.0
network 192.85.20.0
network 192.85.30.0
network 192.85.40.0




R60

interface Loopback0
ip address 60.60.60.60 255.255.255.0
!
interface Loopback1
ip address 192.60.10.1 255.255.255.0
!
interface Loopback2
ip address 192.60.20.2 255.255.255.0
!
interface Loopback3
ip address 192.60.30.3 255.255.255.0
!
interface Loopback4
ip address 192.60.40.4 255.255.255.0
!
interface Ethernet0/0
ip address 10.10.48.2 255.255.255.0
duplex auto
!
interface Ethernet0/1
ip address 10.10.60.1 255.255.255.0
duplex auto
!
interface Ethernet0/2
ip address dhcp
duplex auto
!
interface Ethernet0/3
no ip address
shutdown
duplex auto
!
interface Ethernet1/0
no ip address
shutdown
duplex auto
!
interface Ethernet1/1
no ip address
shutdown
duplex auto
!
interface Ethernet1/2
no ip address
shutdown
duplex auto
!
interface Ethernet1/3
no ip address
shutdown
duplex auto
!
router ospf 1
router-id 60.60.0.60
network 10.10.48.0 0.0.0.255 area 0
network 10.10.60.0 0.0.0.255 area 0
network 60.60.60.0 0.0.0.255 area 0
!
router bgp 65002
bgp log-neighbor-changes
network 60.60.60.0 mask 255.255.255.0
network 192.60.10.0
network 192.60.20.0
network 192.60.30.0
network 192.60.40.0
network 192.168.50.0
neighbor 48.48.48.48 remote-as 65002
neighbor 48.48.48.48 update-source Loopback0
neighbor 52.52.52.52 remote-as 65002
neighbor 52.52.52.52 update-source Loopback0
neighbor 61.61.61.61 remote-as 65002
neighbor 61.61.61.61 update-source Loopback0

I am getting the routes 

R60#sh ip bgp | se 192.43.10.0
*>i 192.43.10.0 61.61.61.61 435200 100 0 ?
R60#sh ip bgp | se 192.47.10.0
*>i 192.47.10.0 61.61.61.61 435200 100 0 ?
R60#sh ip bgp | se 192.86.10.0
*>i 192.86.10.0 61.61.61.61 460800 100 0 ?
R60#

ping failed

R60#ping 192.43.10.1 so
R60#ping 192.43.10.1 source 60.60.60.60
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.43.10.1, timeout is 2 seconds:
Packet sent with a source address of 60.60.60.60
.....
Success rate is 0 percent (0/5)
R60#trace192.43.10.1 source 60.60.60.60
R60#trace 192.43.10.1 source 60.60.60.60
Type escape sequence to abort.
Tracing the route to 192.43.10.1
VRF info: (vrf in name/id, vrf out name/id)
1 10.10.48.1 1 msec 2 msec 1 msec
2 10.10.61.2 2 msec 16 msec 1 msec
3 * * *
4

Re: BGP reachability issue from different AS

R Manjunatha — Mon, 12 Sep 2022 14:08:47 GMT

It’s intended to provide coherent internal connections within an autonomous system while external BGP (eBGP) forms connections between autonomous systems.

we can run OSPF (or EIGRP) within AS and use redistribution between BGP and OSPF. but what if had a full internet routing table? 5000 prefixes . IGPs like OSPF or EIGRP are not able to handle that many prefixes so you’ll need BGP for this.

Re: BGP reachability issue from different AS

Harold Ritter — Wed, 14 Sep 2022 06:28:10 GMT

Hi @R Manjunatha ,

It looks like the traceroute breaks on R85. Can you provide a

show ip route 60.60.60.60

from R85.

Regards,

Re: BGP reachability issue from different AS

MHM Cisco World — Mon, 12 Sep 2022 14:21:17 GMT

full internet is end in Edge router,
inside your AS you need only default route.

I am talking about the SP Core.
but any way I will make small lab show you how you can deal with reachability.

Re: BGP reachability issue from different AS

MHM Cisco World — Mon, 12 Sep 2022 14:45:00 GMT

this is small lab,
all router inside AS-100 with ospf 10 know that any prefix in AS-200 with OSPF 20 is reach via eBGP s3/0 IP
all router inside AS-200 with ospf 20 know that any prefix in AS-100 with OSPF 10 is reach via eBGP s3/0 IP

you can see that in R2 I ping 6.6.6.6 (Lo in R6) wihtout use source because I know that R6 know the R2 IP.
what we need
redistribute OSPF-into-BGP in one site and other site BGP-into-OSPF