Reference Guide

BAckup (HP 28688B and HP 28699A Only)
To configure one of the hub’s ports for dedicated use in a backup (redundant)
link to another hub.
The HP EtherTwist Hub Plus and Hub Plus/48 allow you to use any two of their network
ports for a link to another hub in your network. The backup link normally carries no
traffic, but it is automatically activated if the primary link fails. Note that any of the ports
can be the backup port to any other port.
When you enter the Backup command, you are prompted for these values:
Backup Port The port used for the backup link. Enter the port ID (see the Port
command description for the port IDs). Or, enter 0 if you wish to
remove an existing backup link configuration.
Primary Port The port used for the primary link. Enter the port ID.
Remote Station
Address
The 12-digit hexadecimal station address of the hub at the remote
end of the critical link.
Seconds Between
Test Packets
How often you want the hub to send an IEEE 802.2 Test packet
to the remote hub over the primary link.
Consecutive Failures The number of consecutive Test packet response failures that will
trigger activation of the backup link. For example, enter 5 to
activate the backup link on the fifth failure.
The hub monitors the primary link by sending IEEE 802.2 Test packets at the specified
frequency to the specified remote hub. If “n” consecutive Response packets are not
returned from the remote hub, the primary port is disabled and the backup port is enabled.
When the primary link is repaired, you must reenable the primary port. It is not
automatically reenabled. When the primary port is reenabled, the backup port is disabled
automatically and returned to backup mode. See “Reactivating the Primary Link” in
appendix E, “Backup Links”.
Appendix E contains more information on backup links, including requirements,
limitations, and sample topologies.
Operation 3-3