Tag Archives: Huawei S9300

I have busy time now and a frequency of updating my blog is not such as I would expect. Sorry for that. I hope it should be better soon.

But today I would like to ask you a simple riddle.

Let’s assume that we have S9300 switch and a fragment of its configuration:

#
observe-port 1 interface Ethernet0/0/1
#
acl number 3000
rule 5 deny ip source 89.168.24.0 0.0.0.255
rule 10 deny ip source 91.10.10.0 0.0.0.255
rule 15 permit ip
#
traffic classifier riddle operator and
if-match acl 3000
#
traffic behavior riddle
mirroring to observe-port 1
statistic enable
#
traffic policy riddle
classifier riddle behavior riddle
#
interface Ethernet0/0/10
traffic-policy riddle inbound

Topology Change (TC) packets are sent when MSTP-enabled interface in a network flaps. If a physical interface frequently alternates between Up and Down, the MSTP status of the device in the network becomes unsteady. As a result, a large number of TC messages are generated, ARP entries are frequently deleted and services are interrupted.

How to find the source of TC packets?

Let’s look at the log, generated on one of the switches in a network. Let’s take Huawei S9300 switch as an example:

Dec 19 2012 11:32:56+10:00 S9300 %%01MSTP/6/RECEIVE_MSTITC(l)[40922]:MSTP received BPDU with TC, MSTP process 0 instance 0, port name is GigabitEthernet6/0/0.

What can we find in this log?

The most important for us is the port number on which the switch received TC packet, in this case interface GE6/0/0. To troubleshoot this problem we have to go to the next switch, connected to interface GE6/0/0 and check logs of that switch. If the neighbouring switch receives TC packets as well, we have to do further troubleshooting. If we find in the logs that MSTP-enabled interface is flapping, we can consider that this interface is the source of the TC packet. If this interface is still flapping, just make it down, to avoid unsteady behaviour.