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Port blocked by STP let 1 VLAN passed ...

Cisco SOGET
Level 1
Level 1

Hello

I have a problem with a stack 3750. A port blocked by STP let traffic passed for a VLAN (only one !).

If simebody have an idea ...

Laurent Malandain

1 Reply 1

Amit Singh
Cisco Employee
Cisco Employee

The issue what you are seeing might be unicast flooding on the switch.

 
You can read up on unicast flooding caused by assymetric routing here:
Asymmetric Routing and HSRP (Excessive Flooding of Unicast Traffic in Network with Routers That Run HSRP)
http://www.cisco.com/en/US/customer/tech/tk648/tk362/technologies_tech_note09186a0080094afd.shtml#t8

To combat this issue, you will need to configure the ARP timeout value less than the CAM aging time.

eg.
Router(config)#int vlan 2
Router(config-if)#arp timeout 240

HTH,
Cheers,
-amit singh
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