HP Fiber-Optic Hub Plus User's Guide download pdf (Page 65)

Backup Links

Description

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 Fiber-Optic Hub Plus offers 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), is responsible for

monitoring the link. It sends IEEE 802.2 Test packets to the remote hub (hub B in the

illustration) 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 reenabled.

When the primary link is repaired, you must reenable the primary port. It is not reenabled

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.

“primary” link

“backup” link

(normally inactive)

hub A

“monitoring

hub”

hub B

“remote hub”

802.2 test packets

802.2 response packets

Backup Links E-1

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HP Fiber-Optic Hub Plus User's Guide Page 65