H3C S7500 Series Ethernet Switches Command Manual

Command Manual – MSTP
H3C S7500 Series Ethernet Switches Chapter 1
MSTP Configuration Commands
1-28
View
Ethernet port view
Parameters
None
Description
Use the stp loop-protection command to enable the loop guard function on the
current port.
Use the undo stp loop-protection command to restore the loop guard function to the
default state on the current port.
By default, the loop guard function is disabled.
A switch maintains the states of the root port and other blocked ports by receiving and
processing BPDUs from the upstream switch. These BPDUs may get lost because of
network congestions and link failures. If a switch does not receive BPDUs from the
upstream switch for a certain period, the switch selects a new root port; the original root
port becomes a designated port; and the blocked ports transit to forwarding state. This
may cause loops in the network.
The loop guard function suppresses loops. With this function enabled, if link
congestions or link failures happen, a root port becomes a designated port, and the port
state becomes discarding. The blocked port also becomes designated port and the port
state becomes discarding (that is, the blocked ports do not forward packets), and
thereby loops can be prevented in the network.
Examples
# Enable the loop guard function on Ethernet 2/0/1.
<H3C> system-view
System View: return to User View with Ctrl+Z.
[H3C] interface Ethernet2/0/1
[H3C-Ethernet2/0/1] stp loop-protection
1.1.27 stp max-hops
Syntax
stp max-hops hops
undo stp max-hops
View
System view