Ip route policy, Ip route policy overview, Ip prefix lists – Brocade Network OS Administrator’s Guide v4.1.1 User Manual
Page 561: Route maps, Ip prefix lists route maps
IP Route Policy
IP route policy overview
IP route policy controls how routes or IP subnets are transported from one subsystem to another
subsystem. The IP route policy may perform "permit" or "deny" actions so that matched routes may be
allowed or denied to the target subsystem accordingly. Additionally, IP route policy may also be used for
modify the characteristics of a matched route and IP subnet pair.
Two types of IP route policies are supported, prefix-list and route-map, as discussed in the following
sections
IP prefix lists
An IP prefix list is identified by its name. Each IP prefix list may consist of one or more instances. The
following is an example of IP prefix list,
switch# ip prefix-list test 1 deny 1.2.0.0/16 ge 17 le 30
switch# ip prefix-list test 2 permit 1.1.0.0/16
A matching condition of a prefix-list instance contains two portions: (1) an IP subnet prefix and(2) an
optional prefix (mask) length, where ge (greater than or equal to) is the lower limit of the mask length,
and le (less than or equal to) is the upper limit of the mask length. If no ge or le is given in an instance,
the exact match of subnet prefix length is needed.
In the example above, a route is considered a match for instance 1 if this route is inside subnet
1.2.0.0/16 and whose mask length is between 17 and 30. That is, route 1.2.1.0/24 matches but route
1.2.1.1/32 does not match because of the difference in mask length.
Similar to a route map, when finding a match, each prefix-list instance is looked at in the order specified
by its instance ID. The look-up terminates at the first match. A route that does not find a match in the
prefix list is denied.
At present, a prefix list is not used by itself. The IP prefix list can be used as part of route-map match
clauses. In this context, permit means “match” this pattern, and deny means “do not match this
pattern”.
Route maps
A route map is identified by its name. Each route map may consist of one or more instances. Each route
map instance may contain zero or more match clauses, and zero or more set clauses.
At present, a route map instance represents the largest granularity of configuration. That is, the end
user is required to add and delete route maps by means of its instance. For example, when removing a
route map, an end user is required to remove this route-map in all of its instances. A route map instance
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