Configuring Prefix Lists for BGP Filtering
You do not need to specify a sequence number when removing a configuration entry. Show commands include
the sequence numbers in their output.
Before using a prefix list in a command, you must set up the prefix list.
Procedure
PurposeCommand or Action
Enters the global configuration mode.configure terminal
Example:
Device# configure terminal
Step 1
Creates a prefix list with an optional sequence
number to deny or permit access for matching
ip prefix-list list-name [seq seq-value] deny
| permit network/len [ge ge-value] [le le-value]
Step 2
conditions. You must enter at least one permit or
deny clause.
Example:
Device(config)# ip prefix-list BLUE
permit 172.16.1.0/24
•
network/len is the network number and
length (in bits) of the network mask.
•
(Optional) ge and le values specify the range
of the prefix length to be matched.The
specified ge-value and le-value must satisfy
this condition: len < ge-value < le-value <
32
(Optional) Adds an entry to a prefix list, and assign
a sequence number to the entry.
ip prefix-list list-name seq seq-value deny |
permit network/len [ge ge-value] [le le-value]
Example:
Device(config)# ip prefix-list BLUE seq
10 permit 172.24.1.0/24
Step 3
Returns to privileged EXEC mode.end
Example:
Device(config)# end
Step 4
Verifies the configuration by displaying
information about a prefix list or prefix list entries.
show ip prefix list [detail | summary] name
[network/len] [seq seq-num] [longer]
[first-match]
Step 5
Example:
Device# show ip prefix list summary
test
Routing Configuration Guide, Cisco IOS XE Everest 16.6.x (Catalyst 9500 Switches)
135
Configuring IP Unicast Routing
Configuring Prefix Lists for BGP Filtering
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