BGP experiment (1)

experiment ：

One . Topology

 

Two .1 To configure IP Address

 [r1-LoopBack0]ip add 1.1.1.1 32
[r1-GigabitEthernet0/0/2]ip add 11.1.1.1 24
[r1-GigabitEthernet0/0/1]ip add 12.1.1.1 24
[r2-LoopBack0]ip add 1.1.1.2 32
[r2-GigabitEthernet0/0/2]ip add 22.1.1.1 24
[r2-GigabitEthernet0/0/0]ip add 12.1.1.2 24

[r2-GigabitEthernet0/0/1]ip add 23.1.1.1 24
[r3-GigabitEthernet0/0/0]ip add 23.1.1.2 24
[r3-LoopBack0]ip add 1.1.1.3 32
[r3-GigabitEthernet0/0/2]ip add 33.1.1.1 24
[r3-GigabitEthernet0/0/1]ip add 34.1.1.1 24
[r4-GigabitEthernet0/0/0]ip add 34.1.1.2 24
[r4-LoopBack0]ip add 1.1.1.4 32
[r4-GigabitEthernet0/0/2]ip add 44.1.1.1 24
[r4-GigabitEthernet0/0/1]ip add 45.1.1.1 24
[r4-GigabitEthernet4/0/0]ip add 54.1.1.1 24
[r5-GigabitEthernet0/0/0]ip add 45.1.1.2 24
[r5-GigabitEthernet0/0/1]ip add 54.1.1.2 24
[r5-LoopBack0]ip add 5.5.5.5 24
[r5-GigabitEthernet0/0/2]ip add 55.1.1.1 24

2.AS2 Internal enable OSPF agreement

[r2]ospf 1 router-id 2.2.2.2
[r2-ospf-1-area-0.0.0.0]network 1.1.1.2 0.0.0.0
[r2-ospf-1-area-0.0.0.0]network 22.1.1.1 0.0.0.0
[[r2-ospf-1-area-0.0.0.0]network 23.1.1.1 0.0.0.0
[r3]ospf 1 router-id 3.3.3.3
[r3-ospf-1-area-0.0.0.0]network 23.1.1.2 0.0.0.0
[r3-ospf-1-area-0.0.0.0]network 34.1.1.1 0.0.0.0
[r3-ospf-1-area-0.0.0.0]network 1.1.1.3 0.0.0.0
[r3-ospf-1-area-0.0.0.0]network 33.1.1.1 0.0.0.0
[r4]ospf 1 
[r4]ospf 1 router-id 4.4.4.4
[r4-ospf-1-area-0.0.0.0]network 34.1.1.2 0.0.0.0
[r4-ospf-1-area-0.0.0.0]network 1.1.1.4 0.0.0.0
[r4-ospf-1-area-0.0.0.0]network 44.1.1.1 0.0.0.0

3. Conduct BGP To configure

[r1]bgp 1
[r1-bgp]router-id 1.1.1.1
[r1-bgp]peer 12.1.1.2 as-number 2
[r2]bgp 2
[r2-bgp]router-id 2.2.2.2
[r2-bgp]peer 12.1.1.1 as-number 1

Build a neighborhood
[r3]bgp 2
[r3-bgp]router-id 3.3.3.3 
[r3-bgp]peer 1.1.1.2 as-number 2
[r3-bgp]peer 1.1.1.4 as-number 2
[r3-bgp]peer 1.1.1.4 connect-interface l0
[r4]bgp 2
[r4-bgp]router-id 4.4.4.4
[r4-bgp]peer 1.1.1.3 as-number 2
[r4-bgp]peer 1.1.1.3 connect-interface l0

because BGP The prerequisite for building a neighbor is data level interoperability , therefore , You need to be in R4 Write the static route pointing to the opposite end loopback
[r4]ip route-static 5.5.5.0 24 45.1.1.2
[r4]bgp 2
[r4-bgp]peer 5.5.5.5 as-number 3
[r4-bgp]peer 5.5.5.5 connect-interface l0
[r4-bgp]peer 5.5.5.5 ebgp-max-hop 

because BGP The prerequisite for building a neighbor is data level interoperability , therefore , You need to be in R5 Write the static route pointing to the opposite end loopback
[r5]ip route-static 1.1.1.4 32 45.1.1.1
[r5]ip route-static 1.1.1.4 32 54.1.1.1
[r5]bgp 3
[r5-bgp]router-id 5.5.5.5
[r5-bgp]peer 1.1.1.4 as-number 2
[[r5-bgp]peer 1.1.1.4 connect-interface l0
[r5-bgp]peer 1.1.1.4 ebgp-max-hop 2

Check the neighborhood

 4. The loops of each router are announced in their respective BGP in

[r1]bgp 1
[r1-bgp]net
[r1-bgp]network 11.1.1.0 24

  because IGP The horizontal segmentation mechanism of ,IGP The route learned internally cannot be transmitted to the third router ,R2 and R4 We should also build neighbors , And because of AS-BY-AS Mechanism , The information transmitted internally will not change , Change the next hop when you need to configure delivery

[r2]bgp 2
[r2-bgp]peer 1.1.1.3 next-hop-local
[r2-bgp]peer 1.1.1.4 as-number 2
[r2-bgp]peer 1.1.1.4 connect-interface l0

[r2]bgp 2
[r2-bgp]peer 1.1.1.4 next-hop-local

[r4]bgp 2
[r4-bgp]peer 1.1.1.2 as-number 2
[r4-bgp]peer 1.1.1.2 connect-interface l0

[r4]bgp 2
[r4-bgp]peer 1.1.1.2 next-hop-local
[r4-bgp]peer 1.1.1.3 next-hop-local

[r5]bgp 3
[r5-bgp]network 55.1.1.0 24

test PC Communication between