Reference Guide

examines each prefix list entry to determine if the route’s prefix matches that of the entry. An empty or
nonexistent prefix list permits all prefixes. An implicit deny is assume if a given prefix does not match
any entries of a prefix list. Once a match or deny occurs the router does not go through the rest of the
list. A prefix list may be used within a route map to match a route’s prefix using the match ip
address command (see match ip address on page 537).
Up to 128 prefix lists may be configured. The maximum number of statements allowed in prefix list is 64.
Default No prefix lists are configured by default. When neither the ge nor the le option is configured, the
destination prefix must match the network/length exactly. If the ge option is configured without
the le option, any prefix with a network mask greater than or equal to the ge value is considered
a match. Similarly, if the le option is configured without the ge option, a prefix with a network
mask less than or equal to the le value is considered a match.
Format ip prefix-list list-name {[seq number] {permit | deny}
network/length [ge length] [le length] | renumber renumber-
interval first-statement-number}
Mode Global Configuration
Parameter Description
list-name
The text name of the prefix list. Up to 32 characters.
seq number
(Optional) The sequence number for this prefix list statement. Prefix list statements are
ordered from lowest sequence number to highest and applied in that order. If you do not
specify a sequence number, the system will automatically select a sequence number five
larger than the last sequence number in the list. Two statements may not be configured with
the same sequence number. The value ranges from 1 to 4,294,967,294.
permit Permit routes whose destination prefix matches the statement.
deny Deny routes whose destination prefix matches the statement.
network/
length
Specifies the match criteria for routes being compared to the prefix list statement. The
network can be any valid IP prefix. The length is any IPv4 prefix length from 0 to 32.
ge length (Optional) If this option is configured, then a prefix is only considered a match if its network
mask length is greater than or equal to this value. This value must be longer than the network
length and less than or equal to 32.
le length (Optional) If this option is configured, then a prefix is only considered a match if its network
mask length is less than or equal to this value. This value must be longer than the ge length
and less than or equal to 32.
renumber (Optional) Provides the option to renumber the sequence numbers of the IP prefix list
statements with a given interval starting from a particular sequence number. The valid range
for renumber-interval is 1–100, and the valid range for first-statement-number is 1–1000.
The following example configures a prefix list that allows routes with one of two specific destination
prefixes, 172.20.0.0/16 and 192.168.1.0/24:
(Extreme 220) (Routing)(config)# ip prefix-list apple seq 10 permit 172.20.0.0/16
(Extreme 220) (Routing)(config)# ip prefix-list apple seq 20 permit 192.168.10/24
The following example disallows only the default route.
(Extreme 220) (Routing)(config)# ip prefix-list orange deny 0.0.0.0/0
(Extreme 220) (Routing)(config)# ip prefix-list orange permit 0.0.0.0/0 ge 1
Routing Commands
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