Qtech QSW-2800v2 Руководство пользователя онлайн [188/230] 481607

Qtech QSW-2800v2 Руководство пользователя онлайн [188/230] 481607
Chapter8 Reliability Configuration
8-6
outer root path cost is ERCD. The domain root is RRD. The inner root path
cost is IRCD. The designated bridge ID is D. The designated port ID is PD.
The ID of port receiving BPDU message is PB.
The priority of message received by PB port of bridge B from PD port of
bridge D is higher.
Based on the above assumptions, it will introduce the calculation method of the
priority vector as follow.
(1) Message Priority Vector
The message priority vector is the priority vector carried in the MSTP protocol
message. According to the assumption, The message priority vector received by
the PB port of bridge B is { RD : ERCD : RRD : IRCD : D : PD : PB }.
If the bridge B and bridge D are not in the same domain, the inner root path cost
is meaningless to bridge B and it will be set to be zero.
(2) Interface Priority Vector
In the initial condition, the port priority vector will make itself to be the root. The
port priority vector of PB port is
{ RB : ERCB : RRB : IRCB : B : PB : PB }.
The port priority vector is updated according to the message priority vector
received by port. If the message priority vector received by port is better than the
port priority vector, then the port priority vector is updated to be the message
priority vector. Otherwise, the port priority vector remains constant. Because the
message priority vector received by PB port is better tha the port priority vector,
the port priority is updated to be
{ RD : ERCD : RRD : IRCD : D : PD : PB }.
(3) Root Path Priority Vector
The root path priority vector is calculated by the port priority vector.
If the port priority vector is from the bridge of different domain, the outer root
path cost of the root path priority is the sum of the port path cost and the
outer root path cost of port priority vector. The domain root of root path
priority vector is the local bridge domain root. The inner root path cost is zero.
Supposing that the PB port path cost of bridge B is PCPB, the root path

Содержание

Скачать