HP 200 Series Services And Applications page 95

Bridging Service
Source-Routing Bridging
Configurable Hop-Count Reduction Algorithm
In a source-routing bridging environment, a frame is generally limited to
seven bridge hops. This standard source-routing algorithm counts one hop
per intervening bridge and imposes a limit of seven hops from source-
routing source to source-routing destination. A special HP alternative source-
routing-bridging algorithm called hop count reduction bypasses this limit by
providing an infinite hop capability. This algorithm offers the advantage of
supporting larger diameter networks than were previously possible.
The Hop Count Reduction parameter determines which algorithm is used.
(See the Hop Count Reduction parameter description in the configuration
reference documentation supplied with your router.) The standard source-
routing algorithm is in effect by default. Thus, to allow an infinite number of
hops, set Hop Count Reduction to Yes. But if your network never needs
more than seven hops, it is recommended that you leave this parameter set
to the default No.
Note that, when used with certain network topologies, the hop count
reduction algorithm generates extra explorer frame traffic and multiple
redundant route responses. In certain topologies, such redundant traffic may
be insignificant. In others, end nodes and/or the bridging router may
experience difficulty in detecting loops or routes.
N o t e
Unless the network diameter is greater than seven hops, it is recom-
mended that the hop count reduction algorithm be configured off, so
that the standard seven-hop source-routing algorithm is used. This
minimizes router selection paths and redundant explorer traffic. In
topologies requiring hop-count reduction, you should make efforts to
reduce physical loops around the bridge.
Do not configure the hop count reduction algorithm with source route
translational bridging (TRNSB).
2-43