Configuring
Using the above topology we will configure a single homed eBGP. Download lab here.
On ISP1:
router bgp 101 no synchronization bgp log-neighbor-changes neighbor 192.1.100.2 remote-as 3 no auto-summary !
On ENT1:
router bgp 3 no synchronization bgp log-neighbor-changes network 192.0.101.0 network 192.0.102.0 neighbor 192.1.100.1 remote-as 101 no auto-summary !
All that is left is to use OSPFv2 to distribute routes from FIREWALL to ENT1.
Verifying
To verify just use the following “show” commands.
ISP1#show ip bgp neighbors
BGP neighbor is 192.1.100.2, remote AS 3, external link
BGP version 4, remote router ID 192.1.100.2
BGP state = Established, up for 00:00:42
Last read 00:00:42, last write 00:00:42, hold time is 180, keepalive interval is 60 seconds
... <rest of output deleted>
ISP1#show ip route
Codes: 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
Gateway of last resort is not set
B 192.0.102.0/24 [20/2] via 192.1.100.2, 00:00:50
C 192.1.100.0/24 is directly connected, GigabitEthernet0/0
B 192.0.101.0/24 [20/2] via 192.1.100.2, 00:00:50
ISP1#show ip protocols
Routing Protocol is "bgp 101"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
IGP synchronization is disabled
Automatic route summarization is disabled
Neighbor(s):
Address FiltIn FiltOut DistIn DistOut Weight RouteMap
192.1.100.2
Maximum path: 1
Routing Information Sources:
Gateway Distance Last Update
192.1.100.2 20 00:01:24
Distance: external 20 internal 200 local 200
ISP1#
Perform the same “show” commands on ENT1 to verify association.
Using a ping and traceroute command can check the Layer 3 connectivity for the entire path:
SERV1> ping 192.1.100.1 84 bytes from 192.1.100.1 icmp_seq=1 ttl=253 time=40.158 ms 84 bytes from 192.1.100.1 icmp_seq=2 ttl=253 time=21.494 ms 84 bytes from 192.1.100.1 icmp_seq=3 ttl=253 time=27.591 ms 84 bytes from 192.1.100.1 icmp_seq=4 ttl=253 time=22.309 ms 84 bytes from 192.1.100.1 icmp_seq=5 ttl=253 time=23.390 ms SERV1> trace 192.1.100.1 trace to 192.1.100.1, 8 hops max, press Ctrl+C to stop 1 192.0.101.1 2.539 ms 9.359 ms 9.216 ms 2 10.0.0.1 19.470 ms 20.039 ms 19.656 ms 3 *192.1.100.1 39.910 ms (ICMP type:3, code:3, Destination port unreachable) * SERV1>
Note the exam topics to not mention troubleshooting. Just configuring and verifying….