Westermo RedFox Series - Manual (Page 350)

Westermo OS Management Guide
Version 4.17.0-0
can be configured as an admin edge port.
Access ports and inter-switch ports
It is recommended that all ”inter-switch ports” (ports connecting
switches) are configured as ”non-edge ports” (admin edge disabled),
and that all ”access ports” (ports where hosts connect) are configured
as ”edge ports” (admin edge enabled).
For robustness purposes, all ports are set to ”no admin-edge” when
spanning tree is enabled. To improve performance on ”access ports”
(leading to hosts), these ports should be configured as ”admin-edge”.
When configured as admin edge the port will:
– be put in FORWARDING state quickly after system boot, and
– be kept in FORWARDING state during periods when the spanning tree
topology is changing.
An admin edge assumes the port leads to a host or a router (i.e., not another
bridge), and the port is therefore put in FORWARDING state without first ver-
ifying that the LAN is still loop free. The bridge will still send Hello Messages
on admin edge ports, and will react on any incoming Hello Messages as it
would on regular (non-”admin edge”) ports. Thus, even if loops may occur
via an admin edge port, the bridge will generally be able to receive the high-
priority RSTP messages, and cut the loop by putting the appropriate port in
BLOCKING.
The IEEE std 802.1D-2004 specifies restrictions on the Max age parameter with
respect to the Hello time and the Forward delay as shown below. This affects how
these parameters can be configured.
❼ M ge ≥ 2 ∗ (Heo tme + 1)
❼ M ge ≤ 2 ∗ (Forrd Dey − 1)
Note
Some of the RSTP/STP parameters (Max age, Hello time, and Forward Delay)
need to be set consistently throughout all bridges with the LAN infrastruc-
ture. Therefore, bridges inherit these parameter values from the current root
bridge, irrespective of the corresponding parameter setting in the bridge it-
self.
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