KB.15.15

About Configuring UDLD

When configuring UDLD, keep the following considerations in mind:

• UDLD is configured on a per-port basis and must be enabled at both ends of the link. See the

note below for a list of HP switches that support UDLD.

• To configure UDLD on a trunk group, you must configure the feature on each port of the group

individually. Configuring UDLD on a trunk group's primary port enables the feature on that

port only.

• Dynamic trunking is not supported. If you want to configure a trunk group that contains ports

on which UDLD is enabled, you must remove the UDLD configuration from the ports. After you

create the trunk group, you can re-add the UDLD configuration.

NOTE: UDLD interoperates with the following HP switches: 2600, 2800, 3400, 3500, 4200,

5300, 5400, 6200, 6400, 6600, 8212, and 9300. Consult the release notes and current manuals

for required software versions.

When at least one port is UDLD-enabled, the switch will forward out UDLD packets that arrive on

non-UDLD-configured ports out of all other non-UDLD-configured ports in the same vlan. That is,

UDLD control packets will "pass through" a port that is not configured for UDLD. However, UDLD

packets will be dropped on any blocked ports that are not configured for UDLD.

About Uplink failure detection

Uplink Failure Detection (UFD) is a network path redundancy feature that works in conjunction with

NIC teaming functionality. UFD continuously monitors the link state of the ports configured as

links-to-monitor (LtM), and when these ports lose link with their partners, UFD will disable the set

of ports configured as links-to-disable (LtD.) When an uplink port goes down, UFD enables the

switch to auto-disable the specific downlinks connected to the NICs. This allows the NIC teaming

software to detect link failure on the primary NIC port and fail over to the secondary NIC in the

team.

NIC teams must be configured for switch redundancy when used with UFD, that is, the team spans

ports on both Switch A and Switch B. The switch automatically enables the downlink ports when

the uplink returns to service. For an example of teamed NICs in conjunction with UFD, see Figure 36

(page 108).) For an example of teamed NICs with a failed uplink, see Figure 37 (page 108).

NOTE: For UFD functionality to work as expected, the NIC teaming must be in Network Fault

Tolerance (NFT) mode.

About Uplink failure detection 107