3Com 4007, Release Note

Page: 16 / 128

16 C
HAPTER
2: R
ELEASE
H
IGHLIGHTS
Accelerated
Address Aging
For all Layer 2 Switching Modules in Release 3.0.5, a third option has
been added to the
bridge spanningTree stpState
menu called
agingOnly
(other options are
enable
and
disable
).
Purpose If you select the
agingOnly
option, the Spanning Tree Protocol (STP) is
disabled on the module but the address table’s aging interval will change
(becomes shorter) whenever the module detects that one of its links has
gone down. The objective is to flush addresses as quickly as possible.
Although STP is not operating on the module, this temporary, alternate
aging process draws upon a couple of the STP parameter values. These
can be system defaults or customized values.
How It Works Under normal operating conditions, the Layer 2 module uses the aging
interval value that you set in the
bridge agingTime
command. However,
with the
agingOnly
option selected, whenever a module detects that one
of its links has gone down, the aging interval temporarily changes to the
value that you set in the
bridge spanningTree stpForwardDelay
option. Usually, this interval is much shorter than the
bridge agingTime
and thus addresses age more quickly. After a period of time equal to
bridge spanningTree stpForwardDelay
+
bridge spanningTree
stpMaxAge
seconds has transpired, a module then reverts to using the
value in
bridge agingTime
as the aging interval.
Essentially, the
agingOnly
option mimics the action that STP takes when
ports go down, but does so without having STP enabled on the module.
The accelerated aging process affects all addresses in the Layer 2
module’s address table; it is not limited to the addresses that are
associated with the down port.
This feature was not implemented on Layer 3 modules because it was not
needed. Whether STP is enabled or disabled, whenever a port has gone
down or is disabled, Layer 3 modules immediately flush all addresses that
are associated with that specific port.