Basic configuration of BGP - establish peers and route announcements

The experimental requirements

IGP Configuration of  

Choose one first IGP The agreement guarantees AS2 Internal communication , Here the OSPF. Before that, complete all equipment IP To configure , Now I have been experienced for many days , I won't show more here .

In the face of R2、R3、R4 Conduct OSPF After the configuration , Check whether the routing table of each of them is supplemented

 

 

BGP Building peers  

Here we use the loopback interface to build neighbors , So first write a static route to ensure that the loopback interface can be connected

[R1]ip route-static 2.2.2.0 24 12.1.1.2

[R2]ip route-static 1.1.1.0 24 12.1.1.1

Test with both loops

 

Start building neighbors ---EBGP Between

R1

 

[R1]bgp 1
[R1-bgp]router-id 1.1.1.1
[R1-bgp]peer 2.2.2.2 as-number 2    （ Refers to opposite end ip Address and location as Number ）
[R1-bgp]peer 2.2.2.2 ebgp-max-hop 2（BGP Regulations EBGP All neighbors default BGP Data packets TTL The value is 1, This leads to the lack of hops in the loopback neighbor establishment service , So modify the skip count to enough , Set up here 2）
[R1-bgp]peer 2.2.2.2 connect-interface LoopBack 0 ( The target is the loopback interface )

R2

 

[R2]bgp 2
[R2-bgp]router-id 2.2.2.2
[R2-bgp]peer 1.1.1.1 as-number 1
[R2-bgp]peer 1.1.1.1 ebgp-max-hop 2
[R2-bgp]peer 1.1.1.1 connect-interface LoopBack 0

  After completion, you can see TCP Status of and neighbor table

You can see TCP Of 179 The port status has been  Established

R1 There are also R2

In the same way R2、R3、R4 Between each other  R4、R5 Mutual peer establishment , stay R2、R3、R4 There is no need to modify the number of hops

BGP Announcement of

With R1 For example

[R1]bgp 1
[R1-bgp]network 11.1.1.0 24

stay 2、3 View the routing table

 R2

R3

 

You can find R2 It is superior and R3 It's not good , This is because BGP Of AS-BY-AS Caused by  , To modify

[R2]bgp 2
[R2-bgp]peer 3.3.3.3 next-hop-local

take BGP Route transmission to neighbors 3.3.3.3 Modify the next hop attribute to local （2.2.2.2）

Check again at this time R3 The routing table for

 

  It can be found that it has become excellent

R4 To become excellent, you need to do the same , Similarly, it should be announced R5 When looping back, it needs to be in R4 Modify on

Last in R2、R3、R4 Declare their respective loops , Every loop can go to all AS Autonomous systems

test ： use R1 The loopback of ping R5 The loopback of