BGP Lab - Neighbor Peering and static route injection.

scenario : Let's say Enterprise-1 is connecting to ISP-1 using dual homed design. There are two link which connect to the same ISP. Both link are always alive acting redundancies for each other.

Internal Routers of Enterprise-1, like IE-1 are connecting to their border router E1. In this case i'm using static routes inside the enterprise. If i use other dynamic route like OSPF or etc.., i have to configure "route redistributing" at E1.

And use a loopback interface as update source, and configure eBGP multihop with a dual BGP peer, which reduce the amount of overhead, while giving the same higher availability.

This is the Routing Table of Enterprise Router I-E1.

I-E1#sh ip route

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

i - IS-IS, 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 192.168.100.2 to network 0.0.0.0

192.168.100.0/30 is subnetted, 1 subnets

C 192.168.100.0 is directly connected, FastEthernet0/0

S* 0.0.0.0/0 [1/0] via 192.168.100.2 !! Default Static Route to E1

What I’m trying to do here is just try to set a default route, which saying that any packets which coming to I-E1 will go out to inner interface of Border Enterprise Router E1. Let’s say a packet come in, which want to go to ISP router ISP-1 that I-E1 don’t know. Then I-E1 will send all these into 192.168.100.2 of E1. From here, E1 will take care the rest of its journey by using its Routing table. Here is E1 routing table.

E1#sh ip route

Gateway of last resort is 0.0.0.0 to network 0.0.0.0

1.0.0.0/32 is subnetted, 1 subnets

C 1.1.1.1 is directly connected, Loopback0

2.0.0.0/32 is subnetted, 1 subnets

S 2.2.2.2 [1/0] via 192.168.1.2 !! This is the static route to use loopback interface.

[1/0] via 10.1.1.2

S 192.168.99.0/24 [1/0] via 192.168.100.1

C 10.0.0.0/8 is directly connected, FastEthernet2/0

C 192.168.1.0/24 is directly connected, FastEthernet1/0

192.168.100.0/30 is subnetted, 1 subnets

C 192.168.100.0 is directly connected, FastEthernet6/0

S* 0.0.0.0/0 is directly connected, Loopback0 !! This is default static route all packet via loopback

And, I tried to inject 192.168.100/24 and 192.168.99.0/24, which are internal subnets of Enterprise to advertise out in BGP message of E1. So ISP-1 will receive the route and know how to reach inner subnets or Enterprise.

ISP-1#sh ip route

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

i - IS-IS, 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

1.0.0.0/32 is subnetted, 1 subnets

S 1.1.1.1 [1/0] via 192.168.1.1

[1/0] via 10.1.1.1

2.0.0.0/32 is subnetted, 1 subnets

C 2.2.2.2 is directly connected, Loopback0

B 192.168.99.0/24 [20/0] via 1.1.1.1, 00:03:28

C 10.0.0.0/8 is directly connected, FastEthernet2/0

C 192.168.1.0/24 is directly connected, FastEthernet1/0

B 192.168.100.0/24 [20/0] via 1.1.1.1, 00:03:28

ISP-1#ping 192.168.100.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.100.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 64/94/140 ms

Vice visa,

I-E1#ping 2.2.2.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 172/240/300 ms