Mellanox MLNX-OS User Manual for SX1018HP Ethernet Managed Blade Switch

Rev 2.10
Mellanox Technologies
429
Mellanox Technologies Confidential
5.5 Spanning Tree
The operation of Rapid Spanning Tree Protocol (RSTP) provides for rapid recovery of connectiv-
ity following the failure of a bridge/bridge port or a LAN.
The RSTP component avoids this
delay by calculating an alternate root port, and immediately switching over to the alternate port if
the root port becomes unavailable. Thus, using RSTP, the switch immediately brings the alternate
port to forwarding state, without the delays caused by the listening and learning states. The RSTP
component conforms to IEEE standard 802.1D 2004.
RSTP enhancements is a set of functions added to
increase the volume of RSTP in Mellanox
switches. It adds a set of capabilities related to the behavior of ports in different segments of the
network. For example: the required behavior of a port connected to a non-switch entity, such as
host, is to converge quickly, while the required behavior of a port connected to a switch entity is
to converge based on the RSTP parameters.
Additionally, it adds security issues on a port and switch basis, allowing the operator to deter-
mine the
state and role of a port or the entire switch should an abnormal event occur
. For exam-
ple: If a port is configured to be root-guard, the operator will
not allow it to become a root-port
under any circumstances, regardless of any BPDU that will have been received on the port.
5.5.1 Port Priority and Cost
When two ports on a switch are part of a loop, the STP port priority and port path cost configura-
tion determine which port on the switch is put in
the forwarding state and which port is put in the
blocking state.
To configure port priority use the following command:
switch (config interface etherent <inf>)# spanning-tree port-priority <0-240>
To configure port path cost use the following command:
switch (config interface etherent <inf>)# spanning-tree cost <1-200000000>
5.5.2 Port Type
Port type has the following configuration options:
• edge – is not assumed to be conver
ged by the RSTP learning/forwarding mechanism. It
converges to forwarding quickly.
• normal – is assumed to be connected to a switch, thus it tries to be converged by the
RSTP learning/forwarding. However, if it does not receive any BPDUs, it is operation-
ally moved to be edge.
• network – is
assumed to be connected to a switch. If it does not receive any BPDUs, it
is moved to discarding state.
Each of these configuration options is mutually exclusive.
Port type is configured using the command spanning-tr
e
e port type. It may be applied globally on
the switch (Config) level, which configures all switch interfaces. Another option is to configure
ports individually by entering the interface’s configuration mode.
It is recommended to configure the port type for all ports connected to hosts as edge
ports.