default-route-advertise(IS-IS)

Function

The default-route-advertise command configures the IS-IS routers to generate default route.

The undo default-route-advertise command cancels the configuration.

By default, the IS-IS routers do not generate default route.

Format

undo default-route-advertise

Parameters

Parameter	Description	Value
always	Indicates that default routes are advertised unconditionally, that is, the router can advertise the default route with the next hop as itself.	-
match default	If the default route generated by other routing protocols or other IS-IS processes exists in the routing table, the default route is advertised in the LSP. If the default route is deleted from the routing table, the default route is not advertised in the LSP.	-
route-policy route-policy-name	Specifies the name of the routing policy. If external routes match the routing policy, the default route is advertised in the LSP. The routing policy specified in the default-route-advertise command does not affect the import of external routes by IS-IS.	The name is a string of 1 to 40 case-sensitive characters, with spaces not supported. When double quotation marks are used around the string, spaces are allowed in the string.
cost cost	Specifies the cost of the default route.	The value varies with the cost style. When the cost style is narrow, narrow-compatible or compatible, the value ranges from 0 to 63. When the cost-style is wide or wide-compatible, the value ranges from 0 to 4261412864.
tag tag	Specifies the tag value of the advertised default route. The advertised LSPs contain the administrative tag value only when the IS-IS cost style is wide, wide-compatible, or compatible.	The value is an integer ranging from 1 to 4294967295.
level-1	Sets the level as Level-1.	-
level-2	Sets the level as Level-2.	-
level-1-2	Sets the level as Level-1-2.	-
avoid-learning	Indicates that the default routes to be advertised cannot be the routes learnt by the IS-IS process and then added to the routing table. If the learnt default routes are in active state in the forwarding table, disable this default route.	-

If no level is specified, the level of the default route is Level-2.

Views

IS-IS view, IS-IS topology view, or IS-IS IPv6 topology view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

When IS-IS and other routing protocols are running on a network, use either of the following methods to allow the traffic within the IS-IS domain to be transmitted to other routing domains:

Configure a boundary router in the IS-IS domain to advertise default routes to the IS-IS domain.
Configure a boundary router in the IS-IS domain to import routes from the other routing domains to the IS-IS domain.

The first method is simpler, because the routers in the IS-IS domain do not need to learn routes imported form the other routing protocols.

The default-route-advertise command is used to configure an IS-IS router to advertise default routes to the routers within an IS-IS domain.

Prerequisites

IS-IS processes have been enabled.

Configuration Impact

After this command is run on an IS-IS router, all traffic in an IS-IS domain will be forwarded by this IS-IS router to a destination outside the domain. Compared with configuring a static default route on each router in an IS-IS domain, running this command simplifies configurations, because this command only needs to be run on a boundary router in the IS-IS domain. In addition, you can specify different parameters to allow default routes to be advertised in different ways.

Precautions

You can specify always to allow default routers to be advertised in any case.

You can specify route-policy route-policy-name in the command. After this parameter is specified, a boundary router in the IS-IS domain will advertise default routes to the domain only when the routing table on the boundary router has external routes matching the routing policy. If the routing table on the boundary router does not have specific external routes due to link failures, the boundary router will not advertise default routes to the IS-IS domain, preventing unreachable routes.

This command can be run on an IS-IS router of any level.

If this command is run on a Level-1 router, the router advertises default routes only to the Level-1 area.

Creating a route-policy before it is referenced is recommended. By default, nonexistent route-policies cannot be referenced using the command. If the route-policy nonexistent-config-check disable command is run in the system view and a nonexistent route-policy is referenced using the current command, an ABR advertises the default route to the IS-IS domain as long as the local routing table contains external routes.

Example

# Set the current router to advertise the default IPv4 route , which matches the route-policy named filter, and set the cost to 15.

<sysname> system-view

[sysname] isis

[sysname-isis-1] default-route-advertise route-policy filter cost 15

# Configure the router in a topology instance named red to advertise the IPv4 default routes matching a route-policy named filter, and set the cost of the IPv4 default routes to 15.

<sysname> system-view

[sysname] isis 1

[sysname-isis-1] topology red topology-id 10

[sysname-isis-1-topology-red] default-route-advertise route-policy filter cost 15