How to configure Prefix-List on Cisco Router

Can you explain how the below works

ip prefix-list  -for default route

ip prefix-list le 32 - for all routes


Hello Sims

Remember that unlike an access list, a prefix-list will give you a list of prefixes to match A prefix is composed of a network address with a subnet mask.

Let’s look at the second one first:

ip prefix-list le 32

This will give you a list of prefixes that are composed of and can have subnet masks ranging from 0 to 32. So:

So this essentially states that this prefix list matches all networks (signified by with any subnet mask (signified by le 32).

For the first one, this prefix list will match anything that has a subnet mask of /0. So only the default route will be matched. Any other network/subnet mask combination, such as for example, will not be matched.

I hope this has been helpful!


Hi Rene,

There is an option in IOS where multiple prefix-list can be matched with one statement.

As an example,

match ip address prefix-list satellite_default dmvpn_default

As indicated above satellite_default and dmvpn_default are separate prefix-list

Please explain how this works


1 Like

Hello Talha

When applying a match statement specifically for matching an IP address within a route map, you are able to specify more than one prefix list. Actually, you can specify even more than two. For example:

Router(config-route-map)#$dress prefix-list list1 list2 list3 list4 ?
  WORD  IP prefix-list name

You can see from the above output that after four lists have been entered, there is the option to add an additional one.

The IOS will attempt to match the IP address to the prefix lists in the order they are indicated.
In other words, it will interpret this as a single list that is composed of the concatenated prefix lists, and will go through the statements within those lists in order. Once a match is found, it will not look further.

You are able to do this with access lists as well. See the CLI output below:

Router(config-route-map)#match ip address ACL1 ACL2 ACL3 ACL4 ?
  <1-199>      IP access-list number
  <1300-2699>  IP access-list number (expanded range)
  WORD         IP access-list name

So this is not a characteristic of prefix lists, but of the match statements made within a route-map.

I hope this has been helpful!


1 Like


is it more appropriate to use the deny in a prefix list or in the route map?


ip prefix-list TEST seq 10 deny
ip prefix-list TEST seq 15 permit le 32

route-map TEST permit 10 
 match ip address prefix-list TEST


ip prefix-list TEST seq 10 permit

route-map TEST deny 10 
 match ip address prefix-list TEST
route-map TEST permit 20 

Thanks a lot.



1 Like

Hello Lukas

Both configurations should bring about the same results, and I believe both are acceptable. In my personal opinion, it is preferable to include the detail of what to permit and what to deny in the “lowest level entity” in the configuration. In this case, this would be the prefix list. In other words, since the route-map calls upon the prefix list to define traffic, the route-map is at a higher level of the configuration.

This makes it easier to modify in the future. All of the permit/deny combinations you want are found within the prefix-list, and you only have to edit this list in order to modify the behaviour. Otherwise, you may have to edit both the prefix-list and the route-map.

I hope this has been helpful!



Great answer :slight_smile: Thanks

1 Like

How can i calculate the range in binary ??.

ip prefix-list permit le 7
ip prefix-list permit ge 15

Hello Narad

Let’s take a look at the first prefix list. The address represented in binary is:


I included the dots for clarity. Now, the prefix list is essentially saying that this matches prefixes with the following characteristics:

  1. it matches all prefixes within the range
  2. it matches all prefixes that have a subnet mask less than 7

Looking at this in binary, it says that:

  1. It will match all prefixes that begin with 0111, that is the first four bits of the prefix. In other words it will match any prefix from 01110000.00000000.00000000.00000000 to 01111111.11111111.11111111.11111111. In decimal that is from to
  2. The prefix must also match any subnet mask less than 7.

You can also approach the second prefix-list in the same manner.

I hope this has been helpful!


Hi Dear, One question. how and why prefix list is more powerful than access list?

Hello Zahid

An access list can be used to define a specific range of IP addresses. A prefix list can be used to define a specific range of prefixes. Prefix lists include the subnet mask in their matching mechanisms.

For example, let’s say you want to define a list of prefixes that fall within the range of but have a subnet mask between /25 and /27. To do this with an access list, it would be quite complicated. With a prefix list, you only need a single line:

ip prefix-list MY_LIST permit ge 25 le 27

Remember that access lists will filter specific addresses, prefix lists will filter prefixes (which define a range of addresses since they include subnet masks).

I hope this has been helpful!


Thanks for the help dear

1 Like