|Document revision:||1.2 (Wed Mar 24 12:31:52 GMT 2004)|
Prefix lists are used to filter routes received from or sent to other routers.
SpecificationsPackages required: routing
License required: Level1
Submenu level: /routing prefix-list
Hardware usage: Not significant
Filtering by prefix list involves matching the prefixes of routes with those listed in the prefix list. When there is a match, the route is used. The prefix lists are used when specifying the BGP peers under /routing bgp peer or RIP interfaces under /routing rip interface.
To match a prefix-list entry, a route should have its prefix (i.e. destination address) matching prefix property of the entry, and it should have the length of its prefix (i.e. mask of destination address) matching prefix-length property of the entry.
SetupSubmenu level: /routing prefix-list
Property Descriptionname (name; default: "") - a name for the prefix list default-action (accept | reject; default: accept) - default action for all members of the list
An empty prefix list matches all prefixes
To add a cybernet list that rejects the routes by default:
[admin@MikroTik] routing prefix-list> add name=cybernet default-action=reject [admin@MikroTik] routing prefix-list> print # NAME DEFAULT-ACTION 0 cybernet reject [admin@MikroTik] routing prefix-list>
Prefix List RulesSubmenu level: /routing prefix-list list <listname>
Property Descriptionprefix (IP address mask; default: 0.0.0.0/0) - network prefix to match prefix-length (integer; default: 0-32) - length (range) of the network prefix in bits action (accept | reject; default: accept) - action to perform on list member
There are two different values to match - prefix (i.e. destination address of the route applying the network mask) and prefix length. Prefix length matches network mask of the received route.
For example, if prefix=172.16.0.0/16 and prefix-length=16-24, then received route for 172.16.24.0/24 will match, but route for 172.16.24.0/25 will not.
To accept the routes to the 172.16.0.0/16 network and any of it's subnetworks that has their network mask between 16 and 24:
[admin@MikroTik] routing prefix-list> list cybernet [admin@MikroTik] routing prefix-list list cybernet> add prefix=172.16.0.0/16 \ \... prefix-length=16-24 [admin@MikroTik] routing prefix-list list cybernet> print # PREFIX PREFIX-LENGTH ACTION 0 172.16.0.0/16 16-24 accept [admin@MikroTik] routing prefix-list list cybernet>