Protectio
n
Function
Scenario Principle
Loop
protection
On an RSTP network, a
switching device maintains
the states of the root port and
blocked ports based on RST
BPDUs received from the
upstream switching device.
If the ports cannot receive
RST BPDUs from the
upstream switching device
because of link congestion or
unidirectional link failures,
the switching device re-selects
a root port. Then, the previous
root port becomes a
designated port and the
blocked ports change to the
Forwarding state. As a result,
loops may occur on the
network.
Loop protection can be enabled on the root
and alternate port of a switching device. If
the root port or alternate port does not
receive any RST BPDUs from the
upstream switching device for a specific
period of time, the switching device can
send a notification to the NMS. (The root
port enters the Discarding state in this
case.) The blocked port remains in the
Blocking state and does not forward
packets, preventing loops on the network.
The root port or alternate port restores the
Forwarding state after receiving new RST
BPDUs.
NOTE
Loop protection takes effect only on the root
port and alternate ports.
TC
BPDU
attack
defense
A switching device deletes its
MAC address entries and ARP
entries after receiving TC
BPDUs. If an attacker sends a
large number of bogus TC
BPDUs to the switching
device in a short time, the
device frequently deletes
MAC address entries and ARP
entries. This increases the load
of the switching device and
threatens network stability.
After enabling TC BPDU attack defense
on a switching device, you can set the
number of times the device processes TC
BPDUs within a given time. If the number
of TC BPDUs that the switching device
receives within the given time exceeds the
specified threshold, the switching device
processes only the specified number of TC
BPDUs. Excess TC BPDUs are processed
by the switching device as a whole after
the specified period expires. This function
prevents the switching device from
frequently deleting its MAC address
entries and ARP entries.
6.2.6 RSTP Technology Details
The Proposal/Agreement mechanism enables a designated port to enter the Forwarding state
quickly. As shown in Figure 6-12, root bridge S1 establishes a link with S2. On S2, p2 is an
alternate port; p3 is a designated port and is in the Forwarding state; p4 is an edge port.
Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
6 STP/RSTP Configuration
Issue 01 (2014-11-30) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
185
To Next Page
Loading...
