Extreme Networks ExtremeWare XOS 11.1, Manual

Page: 191 / 496

Routing Policies
ExtremeWare XOS 11.1 Concepts Guide
191
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.