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154 | IP Access Control Lists (ACL), Prefix Lists, and Route-maps
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The following list includes the configuration tasks for prefix lists:
• Configure a prefix list on page 154
• Use a prefix list for route redistribution on page 156
For a complete listing of all commands related to prefix lists, refer to the
FTOS Command Line Interface
Reference document.
Configure a prefix list
To configure a prefix list, use these commands in the following sequence, starting in the
CONFIGURATION mode:
If you want to forward all routes that do not match the prefix list criteria, you must configure a prefix list
filter to permit all routes (
permit 0.0.0.0/0 le 32). The “permit all” filter should be the last filter in your
prefix list. To permit the default route only, enter
permit 0.0.0.0/0.
Figure 8-13 illustrates how the
seq command orders the filters according to the sequence number assigned.
In the example, filter 20 was configured before filter 15 and 12, but the
show config command displays
the filters in the correct order.
Figure 8-13. Command Example: seq
Note the last line in the prefix list Juba contains a “permit all” statement. By including this line in a prefix
list, you specify that all routes not matching any criteria in the prefix list are forwarded.
To delete a filter, use the
no seq sequence-number command in the PREFIX LIST mode.
Step Command Syntax Command Mode Purpose
1 ip prefix-list prefix-name CONFIGURATION Create a prefix list and assign it a unique
name.
You are in the PREFIX LIST mode.
2
seq sequence-number {deny |
permit} ip-prefix [ge
min-prefix-length] [le
max-prefix-length]
CONFIG-NPREFIXL Create a prefix list with a sequence number
and a deny or permit action. The optional
parameters are:
• ge min-prefix-length: is the minimum
prefix length to be matched (0 to 32).
• le max-prefix-length: is the maximum
prefix length to be matched (0 to 32).
FTOS(conf-nprefixl)#seq 20 permit 0.0.0.0/0 le 32
FTOS(conf-nprefixl)#seq 12 deny 134.23.0.0 /16
FTOS(conf-nprefixl)#seq 15 deny 120.23.14.0 /8 le 16
FTOS(conf-nprefixl)#show config
!
ip prefix-list juba
seq 12 deny 134.23.0.0/16
seq 15 deny 120.0.0.0/8 le 16
seq 20 permit 0.0.0.0/0 le 32
FTOS(conf-nprefixl)#