Shulou(Shulou.com)06/01 Report--

1. As-path routing analysis

Attribute

Spread range

Default value

Priority value direction

Note: weight this router this router is 32768, other routers 0 large value priority INCISCO private

Local preferenceAS Internal 100th: border router, advertised to IBGP neighbors, telling how to leave this AS large value priority OUT

No short priority IN and OUT between As pathAS

How to modify the As path value:

Method 1: modify the As path value in the OUT direction, for example

Ip prefix-list 1 seq 5 permit 33.33.33.0/24

Route-map AS permit 10

Match ip address prefix-list 1

Set as-path prepend 2 2 2

Route-map AS permit 20

Router bgp 3

Neighbor 23.1.1.2 route-map AS out

Method 2: modify the As path value in the IN direction, for example

2. Experimental topology

3. Basic configuration

R1 configuration

Interface Loopback0

Ip address 1.1.1.1 255.255.255.0

Interface Serial0/0

Ip address 13.1.1.1 255.255.255.0

Interface Serial0/1

Ip address 14.1.1.1 255.255.255.0

Router ospf 110

Router-id 1.1.1.1

Log-adjacency-changes

Network 1.1.1.0 0.0.0.255 area 0

Network 14.1.1.0 0.0.0.255 area 0

Router bgp 4

No synchronization

Bgp router-id 1.1.1.1

Neighbor 4.4.4.4 remote-as 4

Neighbor 4.4.4.4 update-source Loopback0

Neighbor 4.4.4.4 next-hop-self

Neighbor 13.1.1.3 remote-as 3

No auto-summary

R2 configuration

Interface Loopback0

Ip address 2.2.2.2 255.255.255.0

Interface Serial0/1

Ip address 23.1.1.2 255.255.255.0

Interface FastEthernet1/0

Ip address 24.1.1.2 255.255.255.0

Router ospf 110

Router-id 2.2.2.2

Network 2.2.2.0 0.0.0.255 area 0

Network 24.1.1.0 0.0.0.255 area 0

Router bgp 4

No synchronization

Bgp router-id 2.2.2.2

Neighbor 4.4.4.4 remote-as 4

Neighbor 4.4.4.4 update-source Loopback0

Neighbor 4.4.4.4 next-hop-self

Neighbor 23.1.1.3 remote-as 3

No auto-summary

R3 configuration

Interface Loopback0

Ip address 3.3.3.3 255.255.255.0

Interface Loopback1

Ip address 33.33.33.33 255.255.255.0

Interface Serial0/0

Ip address 13.1.1.3 255.255.255.0

Interface Serial0/1

Ip address 23.1.1.3 255.255.255.0router bgp 3

No synchronization

Bgp router-id 3.3.3.3

Network 3.3.3.0 mask 255.255.255.0

Network 33.33.33.0 mask 255.255.255.0

Neighbor 13.1.1.1 remote-as 4

Neighbor 23.1.1.2 remote-as 4

No auto-summary

R4 configuration

Interface Loopback0

Ip address 4.4.4.4 255.255.255.0

Interface Serial0/1

Ip address 14.1.1.4 255.255.255.0

Interface FastEthernet1/0

Ip address 24.1.1.4 255.255.255.0

Router ospf 110

Router-id 4.4.4.4

Network 4.4.4.0 0.0.0.255 area 0

Network 14.1.1.0 0.0.0.255 area 0

Network 24.1.1.0 0.0.0.255 area 0

Router bgp 4

No synchronization

Bgp router-id 4.4.4.4

Neighbor 1.1.1.1 remote-as 4

Neighbor 1.1.1.1 update-source Loopback0

Neighbor 2.2.2.2 remote-as 4

Neighbor 2.2.2.2 update-source Loopback0

No auto-summary

4. Default routing

According to the eighth rule of BGP routing principle, R4 reaches 3.3.3.0 pick 24 and 33.33.33 pick 24 all pass through R2.

5. Modify the As path value in the OUT direction

R4 to 3.3.3.0Compact 24 and 33.33.330Universe 24 all pass through R2. We change the As path value to make R4 reach 3.3.3.0Universe 24 through R2 and 33.33.33.0Universe 24 through R1.

R3 configuration

Ip prefix-list 1 seq 5 permit 33.33.33.0/24

Route-map AS permit 10

Match ip address prefix-list 1

Set as-path prepend 2 2 2

Route-map AS permit 20

Router bgp 3

Neighbor 23.1.1.2 route-map AS out

6. Modify the As path value in the IN direction

R4 to 3.3.3.0Compact 24 and 33.33.330Universe 24 all pass through R2. We change the As path value to make R4 reach 3.3.3.0Universe 24 through R2 and 33.33.33.0Universe 24 through R1.

R2 configuration

Ip prefix-list 1 seq 5 permit 33.33.33.0/24

Route-map AS permit 10

Match ip address prefix-list 1

Set as-path prepend 2 2 2

Route-map AS permit 20

Router bgp 4

Neighbor 23.1.1.3 route-map AS in

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