Routing Information Filters - 3Com 7700 Configuration Manual

Routing Information
Filters
to enrich its routing knowledge. While importing the routing information, it must
import only the information that meets its conditions.
To implement the routing policy, you must define a set of rules by specifying the
characteristics of the routing information to be filtered. You can set the rules
based on such attributes as destination address and source address of the
information. The rules can be set in advance and then used in the routing policy to
advertise, receive, and import the route information.
The Switch 7700 supports four kinds of filters, route-policy, acl, ip-prefix, and
community-list. The following sections introduce these filters:
Route Policy
■
ACL
■
IP Prefix
■
Community List
■
Route Policy
A route map is used for matching some attributes in given routing information
and the attributes of the information will be set if the conditions are satisfied.
A route map can include multiple nodes. Each node is a unit for match testing,
and the nodes are matched in a sequence-number-based order. Each node
includes a set of if-match and apply clauses. The if-match clauses define the
matching rules and the matching objects are attributes of routing information. The
comparison of if-match clauses for a node uses a series of Boolean and
statements. As a result, a match is found if all the matching conditions specified by
the if-match clauses are satisfied. The apply clause specifies the actions that are
performed after the node match test, concerning the attribute settings of the
route information.
The comparison of different nodes in a route policy uses a Boolean or statement.
The system examines the nodes in the route policy in sequence. Once the route is
permitted by a single node in the route policy, the route passes the matching test
of the route policy without attempting the test of the next node.
ACL
The access control list (ACL) used by the route policy can be divided into three
types: advanced ACL, basic ACL, and interface ACL.
Basic ACL is usually used for routing information filtering, . When the user defines
the ACL, the user defines the range of an IP address or subnet for the destination
network segment address or the next-hop address of the routing information. If
an advanced ACL is used, perform the matching operation by the specified source
address range.
IP Prefix
The function of the ip-prefix is similar to that of the acl, but it is more flexible and
easier for users to understand. When the ip-prefix is applied to routing
information filtering, its matching objects are the destination address information,
domain of the routing information. In addition, in the ip-prefix, you can specify the
IP Routing Policy 99