Application Overview of IP prefix-list routing distribution

corresponding to the distribution of precise control routes, IP prefix-list has a good application.

Topology

R1--r2--r3

From R3 came the route to R2 as follows

172.16.192.0/24

172.16.193.0/24

172.16.199.248/29

R2 to R1 to do the filter output, 192.168.24.13 is the R1 address

R2

Router BGP 65183
No synchronization
BGP log-neighbor-changes
Neighbor 192.168.24.13 Remote-as 4809
Neighbor 192.168.24.13 Prefix-list Filter out

No auto-summary

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If you want to send R1 routing 172.16.192.0/20 after the R2 aggregation, the aggregation command does not apply to that method,

Then need

IP prefix-list Filter seq Permit 172.16.192.0/20

So that only through 172.16.192.0/20,

172.16.192.0/24

172.16.193.0/24

172.16.199.248/29

have been filtered out.

If you want to pass only

172.16.192.0/24

172.16.193.0/24

So

IP prefix-list Filter seq permit 172.16.192.0/20 ge-Le 24

GE is the smallest, le is the largest, if all is 24, it is 172.16.192.0/20 within the range of/24 routing, if the

172.16.192.0/24

172.16.193.0/24

Aggregate into

172.16.192.0/23

is not.

If you want to pass all the 172.16.192.0/20 range inside whatever the mask is, you should

IP prefix-list Filter seq permit 172.16.192.0/20 le 32

Such

172.16.192.0/24

172.16.193.0/24

172.16.199.248/29

Can all pass.

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