If some IS-IS routes are not preferred, configure conditions to filter IS-IS routes. Only IS-IS routes meeting the specified conditions can be added to an IP routing table.
Only routes in an IP routing table can be used to forward IP packets. An IS-IS route can take effect only after it has been added to an IP routing table.
If an IS-IS route does not need to be added to a routing table, configure a basic ACL, an IP prefix, or a routing policy to filter routes so that only IS-IS routes that meet the specified conditions can be added to an IP routing table. IS-IS routes that do not meet the specified conditions cannot be added to the IP routing table nor selected to forward IP packets.
The system view is displayed.
The IS-IS view is displayed.
Run any of the following commands as required:
Run filter-policy { acl-number | acl-name acl-name } import
IS-IS is configured to filter received routes.
Run quit
Return to the system view.
Run acl { name basic-acl-name { basic | [ basic ] number basic-acl-number } | [ number ] basic-acl-number } [ match-order { config | auto } ]
The basic ACL view is displayed.
Run rule [ rule-id ] [ name rule-name ] { deny | permit } [ fragment-type { fragment | non-fragment | non-subseq | fragment-subseq | fragment-spe-first } | source { source-ip-address { source-wildcard | 0 | src-netmask } | any } | time-range time-name | vpn-instance vpn-instance-name ] *
The rule for the basic ACL is configured.
When the rule command is run to configure rules for a named ACL, only the source address range specified by source and the time period specified by time-range are valid as the rules.
If the action specified in an ACL rule is permit, a route that matches the rule will be received or advertised by the system.
If the action specified in an ACL rule is deny, a route that matches the rule will not be received or advertised by the system.
If a route has not matched any ACL rules, the route will not be received or advertised by the system.
If an ACL does not contain any rules, all routes matching the route-policy that references the ACL will not be received or advertised by the system.
In the configuration order, the system first matches a route with a rule that has a smaller number and then matches the route with a rule with a larger number. Routes can be filtered using a blacklist or a whitelist:
Route filtering using a blacklist: Configure a rule with a smaller number and specify the action deny in this rule to filter out the unwanted routes. Then, configure another rule with a larger number in the same ACL and specify the action permit in this rule to receive or advertise the other routes.
Route filtering using a whitelist: Configure a rule with a smaller number and specify the action permit in this rule to permit the routes to be received or advertised by the system. Then, configure another rule with a larger number in the same ACL and specify the action deny in this rule to filter out unwanted routes.
Based on the IP prefix:
Run filter-policy ip-prefix ip-prefix-name import
Based on the route policy:
Run filter-policy route-policy route-policy-name import
The configuration is committed.