Prerequisites for OSPFv3 Route Filtering Using Distribute-List
It is presumed that you have OSPF configured in your network.
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The OSPFv3 route filtering using distribute-list feature allows users to filter the incoming routes that are programmed in routing table, and the outgoing routes that are advertised.
It is presumed that you have OSPF configured in your network.
Users can define a route map to prevent OSPF routes from being added to the routing table. This filtering happens at the moment when OSPF is installing the route in the routing table. This feature has no effect on link-state advertisement (LSA) flooding.
This feature can be useful during redistribution if the user tags prefixes when they get redistributed on Autonomous System Boundary Routers (ASBRs) and later uses the tag to filter the prefixes from being installed in the routing table on other routers. The below mentioned options are available only for distribute-list filtering using route-map.
Users can assign tags to external routes when they are redistributed to OSPF. Then the user can deny or permit those routes in the OSPF domain by identifying that tag in the route-map and distribute-list in or distribute-list out commands.
In OSPF, the external routes could be Type 1 or Type 2. Users can create route maps to match either Type 1 or Type 2 and then use the distribute-list in command to filter certain prefixes. Also, route maps can identify internal routes (interarea and intra-area) and then those routes can be filtered.
When a match is done on the route source, the route source represents the OSPF Router ID of the LSA originator of the LSA in which the prefix is advertised.
When a match is done on the interface, the interface represents the outgoing interface for the route that OSPF is trying to install in the routing table.
When a match is done on the next hop, the next hop represents the next hop for the route that OSPF is trying to install in the routing table.
Note |
The distribute-list in command can be configured to prevent routes from being installed in the global Routing Information Base (RIB). Prior to the implementation of OSPF local RIB (for feature information on OSPF local RIB, see OSPFv2 Local RIB), OSPF would attempt to install a less preferred route (e.g. an inter-area route when the intra-area path is filtered). With OSPF local RIB, only the best route is considered (because this is the only route the local RIB maintains). There is no concept of a "second-best" OSPF route. For more information on the routing algorithm used by Cisco OSPF routers, please refer to RFC 2328. |
Command Mode: Address family mode (address-family ipv4 unicast). Following is the syntax:
[no] distribute-list [<access-list #> | <access-list name>] |
{prefix <name1> gateway <name2>} |
{prefix <name1>} | {gateway <name2>} |
{route-map name} in [<interface>]
[no] distribute-list [<access-list #> | <access-list name>] | [prefix <name>] out
[{ <routing-process> | <interface> }]
Interface: Incoming (used with Inbound filtering) or outgoing (used with outbound filtering) interface.
Routing-process: Source protocol for the route to be filtered.
Step 1 |
Configure OSPFv3.
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Step 2 |
Configure address-family ipv4 unicast.
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Step 3 |
Configure distribute list with the appropriate route-map.
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Step 1 |
Configure OSPFv3.
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Step 2 |
Configure address-family ipv4 unicast.
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Step 3 |
Defines prefix list to be used and the direction for the filter.
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Step 1 |
Configure OSPFv3.
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Step 2 |
Configure address-family ipv4 unicast.
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Step 3 |
Configure distribute list with the appropriate route-map.
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Mode: Address-family mode (address-family ipv6 unicast). Prefix-list and route-map are supported as filtering options. Following is the syntax:
[no] distribute-list prefix-list <name> in [<interface>]
[no] distribute-list route-map <name> in
[no] distribute-list prefix-list <name> out <routing-process>
Interface: Incoming (used with Inbound filtering) or outgoing (used with outbound filtering) interface.
Routing-process: Source protocol for the route to be filtered.
Step 1 |
Configure OSPFv3.
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Step 2 |
Configure address-family ipv6unicast.
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Step 3 |
Define route map.
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Step 1 |
Configure OSPFv3.
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Step 2 |
Configure address-family ipv6 unicast.
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Step 3 |
Define prefix list name.
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Step 4 |
Define filter incoming routing updates.
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Step 1 |
Configure OSPFv3.
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Step 2 |
Configure address-family ipv6 unicast.
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Step 3 |
Define prefix list name.
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Related Topic |
Document Title |
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OSPF commands |
Cisco IOS IP Routing: OSPF Command Reference |
MIBs |
MIBs Link |
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None |
To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs |
Title |
---|---|
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature. |
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Description |
Link |
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The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Feature Name |
Releases |
Feature Information |
---|---|---|
OSPFv3 Route Filtering Using Distribute-List |
Cisco IOS XE Denali 16.3.1 |
The route-map support for OSPFv3 route-filtering using distribute-list is supported. |
Feature Name |
Releases |
Feature Information |
---|---|---|
OSPFv3 Route Filtering Using Distribute-List |
Cisco IOS XE Release 17.4 |
This feature was introduced. |