Concept Guide

The optional parameters are:
• ge min-prefix-length: the minimum prex length to match (from 0 to 32).
• le max-prefix-length: the maximum prex length to match (from 0 to 32).
Example of Assigning Sequence Numbers to Filters
If you want to forward all routes that do not match the prex list criteria, congure a prex list lter to permit all routes (permit
0.0.0.0/0 le 32). The “permit all” lter must be the last lter in your prex list. To permit the default route only, enter permit
0.0.0.0/0.
The following example shows how the seq command orders the lters according to the sequence number assigned. In the example, lter
20 was congured before lter 15 and 12, but the show config command displays the lters in the correct order.
Dell(conf-nprefixl)#seq 20 permit 0.0.0.0/0 le 32
Dell(conf-nprefixl)#seq 12 deny 134.23.0.0 /16
Dell(conf-nprefixl)#seq 15 deny 120.23.14.0 /8 le 16
Dell(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
Dell(conf-nprefixl)#
NOTE: The last line in the prex list Juba contains a “permit all” statement. By including this line in a prex list, you specify that
all routes not matching any criteria in the prex list are forwarded.
To delete a lter, use the no seq sequence-number command in PREFIX LIST mode.
If you are creating a standard prex list with only one or two lters, you can let the system assign a sequence number based on the order in
which the lters are congured. The system assigns lters in multiples of ve.
Creating a Prex List Without a Sequence Number
To create a lter without a specied sequence number, use the following commands.
1 Create a prex list and assign it a unique name.
CONFIGURATION mode
ip prefix-list prefix-name
2 Create a prex list lter with a deny or permit action.
CONFIG-NPREFIXL mode
{deny | permit} ip-prefix [ge min-prefix-length] [le max-prefix-length]
The optional parameters are:
• ge min-prefix-length: is the minimum prex length to be matched (from 0 to 32).
• le max-prefix-length: is the maximum prex length to be matched (from 0 to 32).
Example of Creating a Filter with a Dell Networking OS-Assigned Sequence Numbers
The example shows a prex list in which the sequence numbers were assigned by the software. The lters were assigned sequence
numbers based on the order in which they were congured (for example, the rst lter was given the lowest sequence number). The show
config command in PREFIX LIST mode displays the two lters with the sequence numbers 5 and 10.
Dell(conf-nprefixl)#permit 123.23.0.0 /16
Dell(conf-nprefixl)#deny 133.24.56.0 /8
Dell(conf-nprefixl)#show conf
!
ip prefix-list awe
seq 5 permit 123.23.0.0/16
124
Access Control Lists (ACLs)