I have 2 routers with each connected to a different ISP. Between my two local routers is ibgp.
I went ahead and enabled "synchronization" because before I enabled that each router was advertising the adjacent routers /24 to the local ebgp peer via the ibgp learned route. After i enabled synchronization the ibgp learned route went away and the first router is now just advertising it's /24 and the second router is now just advertising the other /24...but now I cannot reach the second /24 from the internet (138.43.255.0/24)
Im not quite sure why even though the 138.43.255.0/24 is advertised out ISP2/Router2 that its not working. There is a live HSRP address at 138.43.255.254 that should be reachable. The corresponding 138.43.254.254 is also live on ISP1/Router1 and is reachable from the internet
When I access looking-glasses it seems that the 138.43.255.0/24 does not even show as a subnet in the table, but 138.43.254.0/24 does for ISP1
The configs are essentially mirrors of each other so it is unclear why the first /24 is fine but the second is not.
Configs below of both routers
local router 1:
router bgp 397304
synchronization
bgp log-neighbor-changes
bgp bestpath as-path multipath-relax
network 138.43.254.0 mask 255.255.255.0
neighbor External-PeerGroup peer-group
neighbor External-PeerGroup remote-as 577
neighbor External-PeerGroup password 7 xxxxxxxxxxxxxx
neighbor External-PeerGroup ebgp-multihop 2
neighbor External-PeerGroup update-source TenGigabitEthernet0/0/1
neighbor External-PeerGroup version 4
neighbor External-PeerGroup soft-reconfiguration inbound
neighbor External-PeerGroup filter-list 1 out
neighbor Internal-PeerGroup peer-group
neighbor Internal-PeerGroup remote-as 397304
neighbor Internal-PeerGroup update-source Loopback0
neighbor Internal-PeerGroup version 4
neighbor Internal-PeerGroup next-hop-self
neighbor Internal-PeerGroup soft-reconfiguration inbound
neighbor 10.98.2.229 peer-group External-PeerGroup
neighbor 216.208.172.174 peer-group Internal-PeerGroup
!
ip as-path access-list 1 permit ^$
-
#show ip bgp neighbors 10.98.2.229 advertised-routes
BGP table version is 16713661, local router ID is 216.208.172.173
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
*> 138.43.254.0/24 0.0.0.0 0 32768 i
Total number of prefixes 1
mtor1-ifs-rte01#show ip route static
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
10.0.0.0/30 is subnetted, 1 subnets
S 10.98.2.228 [1/0] via 216.208.172.161
138.43.0.0/16 is variably subnetted, 78 subnets, 6 masks
S 138.43.254.0/24 is directly connected, BDI254
!
interface BDI254
ip address 138.43.254.251 255.255.254.0
standby 1 ip 138.43.254.254
standby 1 priority 202
standby 1 preempt
standby 2 ip 138.43.255.254
standby 2 priority 201
standby 2 preempt
!
#####################################
local router 2:
router bgp 397304
synchronization
bgp log-neighbor-changes
bgp bestpath as-path multipath-relax
network 138.43.255.0 mask 255.255.255.0
neighbor External-PeerGroup peer-group
neighbor External-PeerGroup remote-as 852
neighbor External-PeerGroup password 7 xxxxxxxxx
neighbor External-PeerGroup version 4
neighbor External-PeerGroup soft-reconfiguration inbound
neighbor External-PeerGroup filter-list 1 out
neighbor Internal-PeerGroup peer-group
neighbor Internal-PeerGroup remote-as 397304
neighbor Internal-PeerGroup update-source Loopback0
neighbor Internal-PeerGroup version 4
neighbor Internal-PeerGroup next-hop-self
neighbor Internal-PeerGroup soft-reconfiguration inbound
neighbor 209.202.125.25 peer-group External-PeerGroup
neighbor 216.208.172.173 peer-group Internal-PeerGroup
!
ip as-path access-list 1 permit ^$
-
show ip bgp neighbors 209.202.125.25 advertised-routes
BGP table version is 5159590, local router ID is 216.208.172.174
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
*> 138.43.255.0/24 0.0.0.0 0 32768 i
Total number of prefixes 1
show ip route static
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
138.43.0.0/16 is variably subnetted, 78 subnets, 6 masks
S 138.43.255.0/24 is directly connected, BDI254
interface BDI254
ip address 138.43.255.252 255.255.254.0
standby 1 ip 138.43.254.254
standby 1 priority 201
standby 1 preempt
standby 2 ip 138.43.255.254
standby 2 priority 202
standby 2 preempt
!
