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Backup Links
This chapter describes how to use Backup Links on the hub. Topics described
include:
how backup links work
examples of backup links
configuring a backup link
identifying a backup link
indications of backup link activation
reactivating the primary link
How Backup Links Work
In some network configurations a critical link exists, for example between
two workgroups that regularly share or exchange data over the network. To
maintain the integrity of such a critical link, the HP Hub-16M offer a backup
link feature. A backup link is a separate cable run between two hubs that is
automatically enabled if the connection designated as the primary link fails.
The hub on which the redundant link is configured (hub A in the illustration—
the "Monitoring Hub"), is responsible for monitoring the link. It sends IEEE
802.2 Test packets to the hub at the other end of the link (hub B in the
illustration—the "Remote Hub") and looks for response packets from that
hub. If the response packets fail to come back, the primary link is considered
as having failed and the backup link, which had not been carrying any traffic,
is enabled automatically. If the primary link does fail, it is automatically
disabled until it can be repaired and re-enabled.
When the primary link is repaired, you must re-enable the primary port. It is
not re-enabled automatically. When the primary port is enabled, the backup
port is automatically disabled and returned to backup mode. See "Reactivating
the Primary Link" later in this appendix.
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