protocol involved, but these policies are sometimes more efficient and easier to implement than access
lists.
Routing policies can also modify and filter routing information received and advertised by a switch.
The following sections apply to creating and using policies:
Routing Policy File Syntax on page 191
●
Policy Match Conditions on page 192
■
Policy Action Statements on page 194
■
Policy Examples on page 195
●
Routing Policy File Syntax
The policy file contains one or more policy rule entries. Each routing policy entry consists of:
A policy entry rule name, unique within the same policy.
●
Zero or one match type. If no type is specified, the match type is all, so all match conditions must be
●
satisfied.
Zero or more match conditions. If no match condition is specified, every condition matches.
●
Zero or more actions. If no action is specified, the packet is permitted by default.
●
Each policy entry in the file uses the following syntax:
entry <routingrulename>{
if <match-type> {
<match-conditions>;
} then {
<action>;
}
}
Here is an example of a policy entry:
entry ip_entry {
if match any {
nlri
10.203.134.0/24;
nlri
10.204.134.0/24;
} then {
next-hop
192.168.174.92;
origin
egp;
}
}
Policy entries are evaluated in order, from the beginning of the file to the end, as follows:
If a match occurs, the action in the then statement is taken:
●
if the action contains an explicit permit or deny, the evaluation process terminates.
■
if the action does not contain an explicit permit or deny, then the action is an implicit permit, and
■
the evaluation process terminates.
If a match does not occur, then the next policy entry is evaluated.
●
If no match has occurred after evaluating all policy entries, the default action is deny.
●
ExtremeWare XOS 11.1 Concepts Guide
Routing Policies
191