filter-fec-in

Configures LDP inbound or outbound FEC filtering to filter inbound label bindings on a MPLS router.

Syntax

filter-fec-in prefix-list-name
no filter-fec-in prefix-list-name

Command Default

By default, LDP distributes all FECs that are learned locally or from LDP neighbors to all other LDP neighbors.

Parameters

prefix-list-name
Specifies the prefix-list name.

Modes

MPLS LDP configuration mode

Usage Guidelines

Use the no form of this command to remove the FEC filtering configuration.

LDP inbound-FEC filtering allows the control the amount of memory and CPU processing involved in installing and advertising label bindings not used for forwarding. It also serves as a tool to avoid DOS attack. For inbound FEC filter, consider the following:
  • The FECs filtered by the LDP inbound-FEC filter do not install in the forwarding plane or advertise to the upstream neighbors. The FEC remains in the retained state.
  • The LDP inbound-FEC filter are changed directly without deleting the one previously configured. The change automatically applies and triggers the filtering of inbound FECs.
  • Changes to a referenced prefix-list automatically applies to LDP inbound-FEC filtering. This triggers filtering by way of the new configuration, filtering any existing FECs which violate the filter.
  • To allow multiple route filter updates, the device waits for default 10 seconds before notifying the application of the filter change. The time for notification is configurable.
  • When the LDP inbound-FEC filter is not configured, LDP does not filter any inbound FECs.
  • By default, when the prefix-list referenced by the LDP inbound-FEC filter has no configuration, it is an implicit deny. All inbound FECs are filtered out and retained. The behavior is the same when the prefix list is deleted after setting it in the inbound FEC filter configuration. This behavior is consistent with other protocols which use device filters and also with the use of the advertise-fec command for LDP route injection.
  • Inbound FEC filtering is applicable only for Layer 3 FECs and not for VC FECs. Inbound FEC filtering is not applicable for Layer 2 VPNs.

MPLS is supported on the Extreme 8820, SLX 9740, SLX 9640, and SLX 9540 devices only.

Examples

The following example configures the LDP inbound-FEC filter. 

device# configure terminal
device(config)# ip prefix-list list-abc permit 10.20.20.0/24
device(config)# router mpls
device(config-router-mpls)# ldp
device(config-router-mpls-ldp)# filter-fec-in list-abc
9038039-00 Rev AA