Usage Scenario

To change the AS_Path attribute of BGP routes BGP for selecting the optimal route, you can apply a routing policy containing the apply as-path command.

AS_Path is a private attribute of BGP and records all ASs that a route passes through from the local end to the destination address. Using the AS_Path attribute controls route selection and prevents routing loops. If multiple routes are destined for the same destination address, BGP compares the AS_Path lists of these routes and considers the route with the shortest AS_Path list as the optimal route.

Prerequisites

The apply as-path command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, it affects BGP route selection.

Running the apply as-path command changes the path through which network traffic passes. Use this command only when you are familiar with the network topology and impact of the command on services.

Usage Scenario

The apply backup-interface command is used in IP FRR scenarios to configure a backup outbound interface for a route. After IP FRR is enabled, data traffic can be quickly switched to the backup outbound interface if the primary link fails.

Prerequisites

The route-policy command must be used before the apply backup-interface command.

if-match clauses can be used to configure matching rules such as IP prefix lists, and ACLs before a backup outbound interface is configured.

Follow-up Procedure

Reference a configured route-policy in the ip frr (system view) command or the ip frr (VPN instance view) command to configure IP FRR on a public network or VPN.

The apply backup-interface command is usually used together with the apply backup-nexthop command.

For P2P links, a backup next hop is not necessary. For non-P2P links, a backup next hop is necessary.

Usage Scenario

The apply backup-nexthop command is used to configure a backup next hop for a route in IP FRR and VPN FRR scenarios. After IP FRR is enabled, data traffic can be quickly switched to the backup next hop if the primary link fails.

Prerequisites

The route-policy command has been run before the apply backup-nexthop command.

if-match clauses can be used to set matching rules such as interfaces, IP prefix lists, and ACLs before a backup next hop is configured.

Follow-up Procedure

The configured route-policy can be used in the ip frr (system view) command or the ip frr (VPN instance view) command that is run to configure IP FRR for a public or private network. It can also be used in the vpn frr command that is run to enable VPN FRR.

In a VPN FRR scenario, you only need to run the apply backup-nexthop command to configure a backup next hop.

In an IP FRR scenario, you need to run both the apply backup-nexthop and apply backup-interface commands.

On a P2P link, a backup next hop may not be set. On a non-P2P link, the apply backup-nexthop command must be run to configure a backup next hop.

Usage Scenario

When a large and complex network is deployed, traffic flows of different types, such as voice, video, and data, need to be managed separately, with different bandwidth and delays assigned to these traffic flows. In this case, class-based QoS needs to be configured and complex traffic classification needs to be performed. The apply behavior command is used to associate filtered route with a specific traffic behavior.

Prerequisites

Before running the apply behavior behavior-name command, you need to create a traffic behavior.

Meanwhile, certain matching conditions need to be configured to classify routes, such as the AS-Path lost, community attribute list, address prefix list, and route cost.

Precautions

The apply behavior command is mutually exclusive with the apply ip-precedence command and the apply qos-local-id command, and only one of these commands can be configured on a node of a routing policy. For example, if the apply behavior command is configured in the view created by the route-policy test permit node 10 command, configuring the apply qos-local-id command replaces apply behavior command.

Usage Scenario

To delete the community attributes, you can run the ip community-filter command several times to configure community attributes one by one, and apply the routing policy containing the apply comm-filter delete command to delete these community attributes.

The community attribute is a private attribute of BGP. The apply comm-filter delete command takes effect only for BGP routes.

Prerequisites

The apply comm-filter delete command can be used only after the route-policy command is used.

Precautions

After routes meet the filtering conditions, the specified community attributes of these routes are deleted.

1. When the delete operation is configured on a specified community attribute list, only one community attribute can be configured for the specified community attribute list. To delete multiple community attributes, you need to configure multiple community attribute lists. For example, if community attribute list 1 is used to delete 100:100 200:200 from the community attribute 100:100 200:200 carried in a route, you need to perform the following configurations on community attribute list 1:

   [Huawei] ip community-filter 1 permit 100:100

   [Huawei] ip community-filter 1 permit 200:200

   [Huawei] display ip community-filter

   Community filter Number: 1
   permit 100:100
   permit 200:200

   [Huawei] route-policy RP1 permit node 10

   [Huawei-route-policy] apply comm-filter 1 delete

   If multiple community attributes are configured in the same community filter, the apply comm-filter delete command cannot delete these community attributes. To delete the community attributes, you can run the ip community-filter command several times to configure community attributes one by one, and apply the routing policy containing the apply comm-filter delete command to delete these community attributes. For example, the following command cannot delete the community attribute 100:100 200:200 of the route:

   [Huawei] ip community-filter 1 permit 100:100 200:200

   [Huawei] display ip community-filter

   Community filter Number: 1
   permit 100:100 200:200

   [Huawei] route-policy RP1 permit node 10

   [Huawei-route-policy] apply comm-filter 1 delete

2. When the apply community and apply comm-filter delete commands are run on the same node in a routing policy, the system performs the delete operation before the set operation regardless of the sequence in which the two commands are run.

   [Huawei] display route-policy

   Route-policy : 123a

     permit : 10

   Match clauses:

   Apply clauses: a

   apply community 999:9 additive

   apply comm-filter 1 delete

   The following command output shows that community attribute 111:1 of the corresponding BGP route is deleted and community attribute 999:9 is added.

   [Huawei] display ip community-filter

   Community filter Number: 1 

   permit 111:1 

   permit 999:9

Usage Scenario

To identify the BGP routes, you can apply a routing policy containing the apply community command to configure the community attribute of matched BGP routes.

The community attribute is a private attribute of BGP. It simplifies the application of routing policies and facilitates route maintenance and management. A community is a set of destination addresses with the same characteristics. These addresses have no physical boundary and are independent of their ASs. They share one or multiple community attributes, which can be changed or set by running the apply community command.

Prerequisites

The apply community command can be used only after the route-policy command is used.

Precautions

If the apply community command is configured in a routing policy, the community attributes of the BGP routes that match the routing policy are changed according to the configurations in the routing policy.

Assume that the original community name of a BGP route is 30. If this BGP route matches a certain routing policy, the AS number is replaced or added on the basis of the routing policy. For example:

• If the apply community 100 command is run, the community name is changed to 100.
• If the apply community 100 150 command is run, the community name is changed to 100 or 150. That is, the BGP route belongs to two communities.
• If the apply community 100 150 additive command is run, the community name is changed to 30, 100 or 150. That is, the BGP route belongs to three communities.
• If the apply community none command is run, the community attribute of the BGP route is deleted.

Usage Scenario

To change the cost of routes for selecting the optimal route, you can apply a routing policy containing the apply cost command.

Prerequisites

The apply cost command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, it affects route selection.

The costs of imported routes are independent of the routing policy after the undo apply cost command is used to cancel the configuration of route costs.

Usage Scenario

To change the cost type of routes for selecting the optimal route, you can apply a routing policy containing the apply cost-type command.

Prerequisites

The apply cost-type command can be used only after the route-policy command is used.

Precautions

The priority of the apply cost-type clause is higher than that of the apply cost clause, which affects route selection when a routing policy takes effect.

Precautions

Different operations are performed when the apply cost-type internal command is applied to IS-IS routes and BGP routes:

• When the apply cost-type internal command is applied to IS-IS routes:

  Routes are configured as IS-IS internal routes.

• When the apply cost-type internal command is applied to BGP routes:

  When a router advertises a route learned from an IBGP peer to an EBGP peer, if the apply cost-type internal command is run, the router sets the MED value of the route to be advertised to the EBGP peer as the IGP cost of the next hop of the route.

Precautions

Different operations are performed when the apply cost-type internal command is applied to IS-IS routes and BGP routes:

• When the apply cost-type internal command is applied to IS-IS routes:

  Routes are configured as IS-IS internal routes.

• When the apply cost-type internal command is applied to BGP routes:

  When a router advertises a route learned from an IBGP peer to an EBGP peer, if the apply cost-type internal command is run, the router sets the MED value of the route to be advertised to the EBGP peer as the IGP cost of the next hop of the route.

Usage Scenario

The apply dampening command, which is mostly used in BGP, is used to prevent frequent route dampening from affecting routers on the network.

You can configure different route dampening parameters for different nodes in the same routing policy. When route flapping occurs, BGP can use different route dampening parameters to suppress the routes that match the routing policy.

Procedure

If the apply dampening command is run multiple times, the latest configuration overwrites the previous one.

Configuration Impact

If the apply dampening command is run, each time route flapping occurs, BGP adds a certain penalty value to this route.

Precautions

The parameters in this command do not have default values and must be set. The values of reuse, suppress, and ceiling are listed in ascending order: reuse < suppress <ceiling. According to the formula, MaxSuppressTime = half-life-reach x 60 x (ln (ceiling/reuse)/ln (2)), routes are unsuppressed if the value of MaxSuppressTime is less than 1. Therefore, the value of the ceiling/reuse must be great enough so that the value of MaxSuppressTime can be greater than or equal to 1.

Usage Scenario

When controlling inter-AS VPN route receiving and advertising, apply the routing policy that contains the apply extcommunity command to change the RT extended community attribute of matched routes. Currently, only the RT extended community attribute is supported. This command cannot specify an extended community attribute for public routes.

Prerequisites

The apply extcommunity command can be used only after the route-policy command is used.

Precautions

When the routing policy that contains the action is used in the BGP view, BGP IPv4 unicast address view, or BGP IPv6 unicast address view, the action does not take effect.

When a routing policy takes effect, it affects inter-AS VPN route receiving and advertising.

If the keyword additive is not set in the apply extcommunity command, the original extended community attribute is replaced.

Usage Scenario

On a Tunnel-encap-ext network, to specify the Color extcommunity attribute for BGP routes, run the apply extcommunity color command on a PE. After this configuration is performed, the BGP routes to be advertised carry the Color extcommunity attribute, which identifies the PE. The Color extcommunity attribute is used to generate tunnel encapsulation information, so that the PE forwards the packets to a tunnel.

Prerequisites

A route-policy has been configured using the route-policy command.

Configuration Impact

If a route matches the filtering rules of a specified route-policy, the Color extcommunity attribute will be applied to the route.

Precautions

If additive is not specified in the apply extcommunity color command, the newly configured Color extcommunity attribute overwrites the previous one.

The Color extcommunity attribute for BGP routes can be specified only in a VPN import route-policy, VPN export route-policy, or EVPN export route-policy. The attribute cannot be specified in an EVPN import route-policy.

Usage Scenario

To change the next hop address of BGP routes for selecting the optimal route, you can apply a routing policy containing the apply ip-address next-hop command.

The next hop address of a BGP route is set using the policy in the following situations:

• IBGP: Configure the import or export policy for the IBGP peer. If the next hop address configured in the routing policy is unreachable, the IBGP peer adds the corresponding route to the BGP routing table. However, this route is invalid.

• EBGP: Configure the import policy for the EBGP peer. If an export policy is configured, the route destined for the EBGP peer is discarded because the next hop address is unreachable.

Prerequisites

The apply ip-address next-hop command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, it affects BGP route selection.

When a routing policy is specified in the import-route and network commands, the apply ip-address next-hop clause in the routing policy does not take effect.

Usage Scenario

The apply ipv6 next-hop command configures an IPv6 next hop address for a BGP route.

In BGP, the next hop address of a route can be set through the route-policy in the following situations:

• IBGP

  For an IBGP peer, the configured inbound and outbound policies can take effect. If the next hop address configured in the policy is unreachable, the IBGP peer still adds the route to the BGP routing table, but the route is not valid.

• EBGP

  For an EBGP peer, when the policy is used to modify the next hop address of a route, the inbound policy is configured. If the outbound policy is configured, the route is discarded because its next hop is unreachable.

Prerequisites

The apply ipv6 next-hop command can be used only after the route-policy command is used.

After a BGP route matches a route-policy, you can change the IPv6 next hop address of the BGP route.

When a route-policy is being applied in the import-route and network commands, the apply ipv6 next-hop clause in the route-policy does not take effect.

Usage Scenario

After receiving routes, a BGP route receiver matches the attributes of the BGP routes based on the import route-policy, sets the IP precedence, delivers the BGP routes together with the associated QoS parameters, and applies QoS traffic policies to the classified data. In this case, the BGP route receiver can apply QoS policies to the data sent to the destination network segment based on the IP precedence. This applies QoS policies in BGP.

Prerequisites

The apply ip-precedence command can be used only after the route-policy command is used.

Configuration Impact

If a route matches a route-policy, you can change the value of the Precedence field in the IP header. The Precedence field is the first three bits of the Type of Service (ToS) field in the IP header.

Precautions

If an integer is used to specify ip-precedence, the precedence is saved as an integer in the configuration file. If a keyword is used to specify ip-precedence, the precedence is saved as a keyword in the configuration file.

Usage Scenario

A large number of external routes can be imported to IS-IS, which causes extra burdens on IS-IS-enabled devices. To solve this problem, run the apply isis command to set the level of the routes to be imported to IS-IS.

Prerequisites

The apply isis command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, it affects route receiving and advertising in IS-IS.

Usage Scenario

The Local-Pref attribute is a private attribute of BGP. The apply local-preference command sets only the local preference for BGP routes. The Local_Pref attribute is used to determine the optimal route when traffic leaves an AS. When a BGP router obtains multiple routes to the same destination address but with different next hops through IBGP peers, the route with the largest Local_Pref value is selected.

Prerequisites

The apply local-preference command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, it affects BGP route selection.

The Local_Pref attribute applies to the routing within an AS rather than be advertised to the outside of the AS. In this case, the apply local-preference command does not take effect when EBGP neighbor relationships are set up.

After the apply local-preference command is run in a route-policy or its configuration is changed, route updates are triggered.

Usage Scenario

In the scenario where inter-AS VPN Option C or Carrier Support Carrier (CSC) is deployed, you can use the apply mpls-label command to allocate labels to public routes.

Prerequisites

The apply mpls-label command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, it allocates MPLS labels to public routes.

Usage Scenario

To change the Origin attribute of routes for selecting the optimal route, you can apply a routing policy containing the apply origin command. The Origin attribute is a private attribute of BGP and defines the origin of a route.

Prerequisites

The apply origin command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, it affects BGP route selection.

Usage Scenario

The apply ospf command can be used to specify the OSPF backbone area or NSSA area to which routes are imported. This can prevent OSPF from importing too many external routes, which brings heavy burden on OSPF devices.

Prerequisites

The apply ospf command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, routes are imported to the specified OSPF area.

Usage Scenario

To change the preference of routes for selecting the optimal route, you can apply a routing policy containing the apply preference command.

Prerequisites

The apply preference command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, it affects route selection.

Usage Scenario

To change the preferred value of BGP routes for selecting the optimal route, you can apply a routing policy containing the apply preferred-value command.

Prerequisites

The apply preferred-value command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, it affects BGP route selection.

The preferred value of a route indicates the weight of the route in BGP routing. The preferred value is not a standard RFC-defined attribute and is valid only on local devices. The preferred value is inapplicable to export policies of BGP.

Usage Scenario

The QoS local ID is a local identifier of QoS. In actual applications, you can set the QoS local ID in the route-policy, and add the command that matches the QoS local ID in the QoS policy. The QoS local ID set in the route-policy is delivered to the FIB table. During packet forwarding, the system obtains the QoS local ID from the FIB table and applies the related QoS policy according to the QoS local ID.

Configuration Impact

The apply qos-local-id command is mutually exclusive with the apply behavior and apply ip-precedence commands, and only one of these commands can be configured on a node of a routing policy. For example, if the apply qos-local-id command is configured in the view created by the route-policy test permit node 10 command, configuring the apply ip-precedence command replaces apply qos-local-id command.

Usage Scenario

To identify the routes, you can apply a routing policy containing the apply tag command to add the same tag to the matched routes.

Prerequisites

The apply tag command can be used only after the route-policy command is used.

Precautions

When a routing policy takes effect, routes will be matched by routing policies related to the tag.

BGP routes do not support tags. The apply tag command sets the tag for only IGP routes.

Usage Scenario

On a Tunnel-encap-ext network, if the VN ID of VPN-out on the Hub device differs from the VN ID of a PE, you can run the apply vn-id command on the RR to change the VN ID of EVPN routes in the export route-policy to be the same as the VN ID of VPN-out. This ensures that traffic is routed through the Hub-CE link.

Precautions

This command takes effect only in EVPN export route-policies and VPN import route-policies.

Usage Scenario

The description command can be used to configure a description for a created route-policy. If many route-policies have been configured, configuring descriptions for the policies will facilitate policy management.

Prerequisites

A route-policy has been created by using route-policy command.

Usage Scenario

The AS_Path attribute is a BGP-specific attribute. An AS_Path filter is used to filter BGP routes.

Precautions

Usage Scenario

The community attribute is a BGP-specific attribute. A community filter is used to filter BGP routes.

Precautions

Usage Scenario

Usage Scenario

The extended community attribute is a BGP-specific attribute. An extended community filter is used to filter VPN routes.

Precautions

Usage Scenario

Precautions

Before collecting the number of routes that do or do not match the route-policy in an IPv4 prefix list within a certain period, run the reset ip ip-prefix command to clear existing statistics.

If The specified filter list does not exist is displayed in the command output, the specified IPv4 prefix list failed to be configured. To re-configure it, run the ip ip-prefix command in the system view.

Usage Scenario

Precautions

Before collecting the number of routes that do or do not match the route-policy in an IPv6 prefix list within a certain period, run the reset ip ipv6-prefix command to clear existing statistics.

Usage Scenario

The RD attribute is carried in VPN routes. An RD filter is used to filter VPN routes.

Precautions

To the configuration of the Route-Policy, run display route-policy command.

Usage Scenario

The relationship among the matching rules of nodes in the same route-policy is OR. Specifically, if a route matches a node, it matches the route-policy and is no longer matched against other nodes. If you want the route to be matched against two or more nodes, run the goto next-node [ node ] command so that the route is further matched against a specified node after the route matches the current node.

If node is not specified in the command, the route will be further matched against the next node of the current node by default.

If the node specified in the command does not exist, the route will be further matched against the next node of the specified node by default. If the next node of the specified node does not exist either, the route fails to match the route-policy, and no apply clause will be applied to the route.

Precautions

If the goto next-node command is run in the route-policy view and a route matches all the specified nodes, the apply clauses of these nodes will be applied to the route.

If the route fails to match one node, the route is matched against the next node until it succeeds in matching a node, and then the apply clauses of the nodes that the route matches will be applied to the route. If the route fails to match all nodes, no apply clauses will be applied to the route.

If the goto next-node command is run for multiple nodes, and QoS policy propagation on BGP (QPPB) policies are configured for these nodes using one or more of the apply ip-precedence, apply qos-local-id, apply behavior, and apply traffic-index commands, only the configuration of the last node takes effect.

In the same route-policy, a maximum of 50 nodes can be specified using the command.

In the same route-policy, if this command is configured to match routes against multiple nodes, a maximum of 10 AS numbers, 16 RT extended community attributes, 16 color extended community attributes, and 36 community attributes can be added to the routes that match the nodes; if multiple community filters are used in the same route-policy to delete community attributes from the routes that match filtering conditions, only the first community filter takes effect.

Usage Scenario

You can run the if-match acl command to set a matching rule based on the ACL to match IPv4 prefixes.

Prerequisites

The if-match acl command can be used only after the route-policy command is used.

Precautions

The routing policy matches routes using the ACL. Routes that match the ACL will be checked by other if-match clauses of this node. Routes that do not match the ACL will be checked by the next node.

An ACL name is a character string that starts with a letter. For example, 2a is an invalid ACL name.

The if-match acl command and the if-match ip-prefix command are mutually exclusive. If you run the if-match ip-prefix command after running the if-match acl command, the configuration of the if-match ip-prefix command overrides the configuration of the if-match acl command.

For a named ACL, when the rule command is used to configure a filtering rule, the filtering rule is effective only with the source address range that is specified by the source parameter and with the time period that is specified by the time-range parameter.

Usage Scenario

The AS_Path attribute is the private attribute of BGP. The if-match as-path-filter command is applicable to only BGP routes. The ip as-path-filter command must be used to define an AS_Path filter so that the matching rule based on this AS_Path filter can take effect. For example:

• If the if-match as-path-filter 1 command is used but AS_Path filter 1 is not configured, all routes are permitted, that is, all routes match the matching rule.
• If the if-match as-path-filter 1 command after the ip as-path-filter 1 permit *20 command is used, the BGP routes with the AS_Path attribute being 20 are permitted.

Multiple if-match as-path-filter clauses can be specified. The relationship between if-match as-path-filter clauses is "OR". The relationship between if-match clauses is "AND".

Prerequisites

Before running the if-match as-path-filter command, run the ip as-path-filter command to configure an AS_Path filter.

Precautions

The routing policy matches routes using the AS-Path filter. Routes that match the AS-Path filter will be checked by other if-match clauses of this node. Routes that do not match the AS-Path filter will be checked by the next node.

A maximum of 16 AS_Path filters can be specified. The relationship between these AS_Path filters is OR. Specifically, if a route matches one of these AS_Path filters, it matches the matching rules of the command.

Usage Scenario

Extended community attributes help flexibly control a route-policy. To enable a node to filter routes based on an extcommunity filter, run the if-match extcommunity-list command. This configuration sets a matching rule that is based on the extcommunity filter. The action specified by the apply clause can be performed to change certain route attributes only when the routing information matches the matching rule.

The if-match extcommunity-list command must be used together with the ip extcommunity-list command. For example:

• If the if-match extcommunity-list color aa command is run but the extcommunity-filter color aa command is not run, all the routes are permitted.
• If both the if-match extcommunity-list color aa command and the ip extcommunity-list color basic aa permit 10 command are run, routes with the Color value being 10 are permitted.

Configuration Impact

Routes are filtered based on extcommunity attributes. Those with the specified extcommunity attributes are permitted and those without the specified extcommunity attributes are denied.

Usage Scenario

The community attribute is a private attribute of BGP. The if-match community-filter command is applicable to only BGP routes. The ip community-filter command must be used to define a community filter so that the matching rule based on this community filter can take effect. For example:

• If the if-match community-filter 1 command is used but community filter 1 is not configured, all routes are permitted, that is, all routes can match the matching rule.
• If the if-match community-filter 1 command is used after the ip community-filter 1 permit 1:1 command is used, the BGP routes with the community attribute being 1:1 are permitted.

Multiple if-match community-filter clauses can be specified. The relationship between if-match community-filter clauses is "OR". The relationship between if-match clauses is "AND".

Prerequisites

Before using the if-match community-filter command, you must use the ip community-filter command to configure a community filter.

The if-match community-filter command can be used only after a route-policy is configured by using the route-policy command.

Precautions

The routing policy matches routes using the community filter. Routes that match the community filter will be checked by other if-match clauses of this node. Routes that do not match the community filter will be checked by the next node.

A maximum of 16 community filters can be configured in the if-match community-filter command.

The parameter whole-match is valid only for its front community filter number. If multiple community filters are specified in the if-match community-filter command and packets are required to completely match each filter, you need to specify the parameter whole-match behind each community filter and it is valid to only the basic community filter.

The name of a community filter cannot be all numerals.

Usage Scenario

You can use the if-match cost command to configure a node to filter routes based on the route costs. After such a matching rule is configured, you can apply the apply clauses to change the attributes of the routes that match the matching rule.

Prerequisites

The if-match cost command can be used only after the route-policy command is used.

Precautions

The routing policy matches routes based on the route cost. Routes that match the route cost will be checked by other if-match clauses of this node. Routes that do not match the route cost will be checked by the next node.

Usage Scenario

The extended community attributes help flexibly control the routing policy. You can use the if-match extcommunity-filter command to configure a node to filter routes based on the extended community filter.

The if-match extcommunity-filter command is applicable to only BGP routes and must work in conjunction with the ip extcommunity-filter command. For example:

• If the if-match extcommunity-filter 1 command is used but the extended community filter 1 is not configured, all routes are permitted, that is, all routes can match the matching rule.
• If the if-match extcommunity-filter 1 command is used after the ip extcommunity-filter 1 permit rt 1:1 command is used, the BGP routes with the extended community attribute being 1:1 are permitted.

Multiple if-match extcommunity-filter clauses can be specified. The relationship between if-match extcommunity-filter clauses is "OR". The relationship between if-match clauses is "AND".

Prerequisites

Before using the if-match extcommunity-filter command, you must use the ip extcommunity-filter command to configure an extended community filter.

Precautions

The routing policy matches routes using the extended community filter. Routes that match the extended community filter will be checked by other if-match clauses of this node. Routes that do not match the extended community filter will be checked by the next node.

A maximum of 16 extended community filters can be configured in the if-match extcommunity-filter command. The relationship between these AS_Path filters is OR. Specifically, if a route matches one of these AS_Path filters, it matches the matching rules of the command.

Usage Scenario

An extcommunity filter can be used as a matching condition in a route-policy.

The relationship between the rules configured in an extcommunity list is OR.

For example, a Color extcommunity list can be configured in either of the following formats, and the filtering result is the same.

Format 1:

ip extcommunity-list color basic aa permit 10 20

Format 2:

ip extcommunity-list color basic aa permit 10

ip extcommunity-list color basic aa permit 20

To delete the extcommunity filter of a single node, run the undo ip extcommunity-list command.

To view the detailed configuration of an extcommunity filter, run the display ip extcommunity-list command.

Follow-up Procedure

Run the route-policy-change notify-delay command to set a delay for the RM module to instruct the protocols to re-apply the route-policy after the route-policy changes.

Configuration Impact

The ip extcommunity-list command is used to filter routes based on the Color attribute. The routes that hit the if-match clause are permitted and the unmatched routes are denied.

Precautions

By default, an extended community filter works in deny mode. Specifically, a route that has not been permitted in a filtering is denied by this extcommunity filter. If all matching rules in an extcommunity filter work in deny mode, all routes are denied by the filter. To prevent this problem, configure one matching rule in permit mode after one or multiple matching rules in deny mode so that the routes except for those denied by the preceding matching rules are permitted by the filter.

Usage Scenario

The if-match interface command is used to filter routes based on the outbound interfaces.

A maximum of 16 outbound interfaces can be configured in this command.

If a node contains multiple if-match interface clauses, the relationship between the if-match interface clauses is OR. If a node contains both if-match interface clauses and other if-match clauses with different matching rules, the relationship between the if-match interface clauses and other if-match clauses is AND. For example, if a node contains if-match interface 10ge1/0/1, if-match interface 10ge1/0/2, and if-match acl 2000 clauses, if-match interface 10ge1/0/1 and if-match interface 10ge1/0/2 are ORed, whereas if-match interface 10ge1/0/1 and if-match acl 2000 are ANDed.

Prerequisites

The if-match interface command can be used only after the route-policy command is used.

Precautions

The routing policy matches routes based on outbound interface information. Routes that match the outbound interface information will be checked by other if-match clauses of this node. Routes that do not match the outbound interface information will be checked by the next node.

Usage Scenario

An ACL or IP prefix must be configured before running the if-match ip command so that the matching rule can take effect. For example:

• If the if-match ip next-hop ip-prefix aa command is used but the IP prefix aa is not configured, all routes are permitted, that is, all routes match the matching rule. This rule also applies to ACL.

• If the if-match ip next-hop ip-prefix aa and ip ip-prefix aa permit 10.1.1.1 32 commands are used, the routes with the next hop being 10.1.1.1 is permitted. This rule also applies to ACL.

Prerequisites

The if-match ip command can be used only after the route-policy command is used.

Before running the if-match ip command, configure an ACL or an IP prefix.

Precautions

The routing policy matches routes based on the next hop address or source address. Routes that match the next hop address or source address will be checked by other if-match clauses of this node. Routes that do not match the next hop address or source address will be checked by the next node.

If the next hop address or source address of a route is 0.0.0.0, the system considers the mask length of the route as 0 to match the filtering rules by default.

If the next hop address or source address of a route to be filtered is not 0.0.0.0, by default, the system considers the mask length as 32 and matches the route.

When you run the rule command to configure a filtering rule in a named ACL, only the source and time-range parameters are valid for the filtering rule.

Usage Scenario

The routing policy matches routes using the IP prefix list. Routes are either permitted or denied.

The ip ip-prefix command must be used so that the matching rule can take effect. For example:

• If the if-match ip-prefix aa command is used but the IP prefix aa is not configured, all routes are permitted, that is, all routes match the matching rule.
• If the if-match ip-prefix aa and ip ip-prefix aa permit 10.1.1.1 32 commands are used, the routes with the IP prefix being 10.1.1.1 and mask being 32 are permitted.

Prerequisites

The if-match ip-prefix command can be used only after the route-policy command is used.

Precautions

The routing policy matches routes based on IP prefix information. Routes that match the IP prefix information will be checked by other if-match clauses of this node. Routes that do not match the IP prefix information will be checked by the next node.

The if-match acl and if-match ip-prefix commands cannot be used together in the same node of a routing policy, because the latest configuration will override the previous one.

Usage Scenario

The ip ipv6-prefix command must be used to configure an IPv6 prefix so that the matching rule (based on the destination addresses, next hop addresses, or source addresses of IPv6 routes) configured through the if-match ipv6 command can take effect. Otherwise, all routes are permitted.

Prerequisites

The if-match ipv6 command can be used only after the route-policy command is used.

Before using the if-match ipv6 command, you must use the ip ipv6-prefix command to configure an IPv6 prefix.

Configuration Impact

When you filter routes based on the destination addresses, next hop addresses, or source addresses of IPv6 routes, the routes that match the matching rule are permitted and the routes that do not match the matching rule are denied.

If the next hop address or source address of a route to be filtered is 0::0, by default, the system matches the route considering that its mask length is 0.

If the next hop address or source address of a route to be filtered is not 0::0, by default, the system matches the route and considers its mask length as 128.

Creating an IPv6 prefix list before it is referenced is recommended. If a nonexistent IPv6 prefix list is referenced using the command, all routes match the IPv6 prefix list.

Usage Scenario

In the scenario where inter-AS VPN Option C or Carrier Support Carrier (CSC) is deployed, you can use the if-match mpls-label command to allocate labels to public routes.

Prerequisites

The if-match mpls-label command can be used only after the route-policy command is used.

Precautions

The routing policy matches routes based on the MPLS label. Routes that match the MPLS label will be checked by other if-match clauses of this node. Routes that do not match the MPLS label will be checked by the next node.

Usage Scenario

The if-match rd-filter command and the ip rd-filter command work together to filter routes based on RD attributes. For example:

• If if-match rd-filter 1 is configured, but rd-filter 1 is not configured, then all current routes will be permitted.

• If if-match rd-filter 1 is configured, and ip rd-filter 1 permit 1:1 has been configured, then routes with RD 1:1 will be permitted.

Prerequisites

The if-match rd-filter command must be run after the route-policy command is run.

Precautions

The routing policy matches routes using the RD filter. Routes that match the RD filter will be checked by other if-match clauses of this node. Routes that do not match the RD filter will be checked by the next node.

Usage Scenario

You can run the if-match route-type command to filter OSPF or IS-IS routes based on the route type.

Multiple if-match route-type clauses can be specified. The relationship between if-match route-type clauses is "OR". The relationship between if-match clauses is "AND".

Prerequisites

The if-match route-type command can be used only after the route-policy command is used.

Precautions

The routing policy matches routes based on the route type. Routes that match the route type will be checked by other if-match clauses of this node. Routes that do not match the route type will be checked by the next node.

For the same node in a routing policy, if two if-match route-type clauses are the same, the latter if-match route-type will not override the previous if-match route-type. After the latter clause is configured, both clauses take effect simultaneously. The relationship between if-match route-type clauses is "OR". That is, the actions defined by apply clauses can be performed on a route as long as the route meets one of the matching rules. For example, if both the if-match route-type is-is-level-1 and if-match route-type external-type1or2 commands are configured on the same node of a route policy, both IS-IS Level-1 routes and OSPF external routes can match the route policy.

external-type1or2 refers to external-type1 or external-type2. For the same node in a route policy, configuring both the if-match route-type external-type1 and if-match route-type external-type2 is equivalent to configuring the if-match route-type external-type1or2 command. The two operations generate the same configuration file.

Similarly, nssa-external-type1or2 refers to nssa-external-type1 or nssa-external-type2. For the same node in a route policy, configuring both the if-match route-type nssa-external-type1 and if-match route-type nssa-external-type2 commands is equivalent to configuring the if-match route-type nssa-external-type1or2 command. The two operations generate the same configuration file.

Usage Scenario

You can run the if-match tag command to filter routes based on the tags.

Prerequisites

The if-match tag command can be used only after the route-policy command is used.

Precautions

The routing policy matches routes based on the route tag. Routes that match the route tag will be checked by other if-match clauses of this node. Routes that do not match the route tag will be checked by the next node.

Usage Scenario

An AS_Path filter uses the regular expression to define matching rules. After an AS_Path filter is set, the RM module immediately instructs each protocol to apply the filter by default.

The AS_Path attribute is a private attribute of BGP, and is used to filter BGP routes.

• The filter can be directly applied by using a command such as peer as-path-filter.

• The filter can be used as a matching condition of a routing policy by using a command such as if-match as-path-filter zz.

Configuration Impact

Multiple rules, permit or deny, can be specified in an AS_Path filter. The relationship between theses rules is "OR". This means that if a route meets one of the matching rules, the route matches the AS_Path filter.

By default, AS_Path filters work in deny mode. If all matching rules in a filter are configured to work in deny mode, all routes are denied by the filter; to prevent this problem, configure one matching rule in permit mode after one or multiple matching rules in deny mode so that the routes except for those denied by preceding matching rules are permitted by the filter.

Follow-up Procedure

To view detailed configurations of the AS_Path filter, run the display ip as-path-filter command.

Usage Scenario

The community attribute is a private attribute of BGP, and can be used only to filter BGP routes. The community attribute can be used as a matching rule of a routing policy by using the ip community-filter and if-match community-filter commands together.

Precautions

Only the community number or known community attribute can be specified for a basic community filter. The regular expression can be used as a matching rule in an advanced community filter.

• The ip community-filter basic comm-filter-name command or the ip community-filter basic-comm-filter-num command can be used to configure a basic community filter. basic comm-filter-name specifies the name of a basic community filter, and the name cannot be all digits. A maximum of 20 community numbers can be configured in one command. basic-comm-filter-num specifies only the basic community filter with the number ranging from 1 to 99. A maximum of 20 community numbers can be configured in one command.

• The ip community-filter advanced comm-filter-name command or the ip community-filter adv-comm-filter-num command can be used to configure an advanced community filter. advanced comm-filter-name specifies the name of an advanced community filter, and the name cannot be all digits. adv-comm-filter-num specifies only the advanced community filter with the number ranging from 100 to 199.

The relationship between the rules of the community filter is "AND". This is different from the RD filter. This is because each route has only one RD but can have multiple communities.

For example, the community filters in the following formats have different matching results:

ip community-filter 1 permit 100:1 200:1 300:1

ip community-filter 1 permit 100:1

ip community-filter 1 permit 200:1 300:1

In the preceding configuration of the community filter, the community defined in each rule must be a sub-set of route communities so that the rule can be matched.

The apply comm-filter delete command run in the Route-Policy view deletes the specified community attribute from routes. An ip community-filter command can be used to specify community attributes but one such command specifies only one community attribute each time. To delete more than one community attribute, run the ip community-filter command multiple times. If multiple community attributes are specified in one filter, none of them can be deleted. For information about examples, see apply comm-filter delete.

A community filter must have been configured using the ip community-filter command before the filter is referenced by another command using comm-filter-num or comm-filter-name.

A community filter cannot be deleted using the undo ip community-filter command when it is being referenced using comm-filter-num or comm-filter-name. To delete the community filter, cancel the reference configuration first.

By default, Community filters work in deny mode. If all matching rules in a filter are configured to work in deny mode, all routes are denied by the filter; to prevent this problem, configure one matching rule in permit mode after one or multiple matching rules in deny mode so that the routes except for those denied by preceding matching rules are permitted by the filter.

Follow-up Procedure

Run the display ip community-filter command to view detailed configuration for the community filter.