Description: | Symptom:
Cat3650 running 3.6.2ae. Using converged access for wireless. We had one 3650 as MC and 4 3650 as MA in our setup. However, I believe this will be able to be reproduced with just one switch.
DHCPv6 solicit frame (IPv6 multicast) are sent from a wired devices (AP or WYSE terminal in our case) on an access port in VLAN25. The same frame is sent out of the switch uplink and to other access ports in VLAN25 15 times. As the frame traverses the next switch that is in the same state, each frame gets multiplied 15 times again causing a storm of DHCPv6 frames. In our case, this storm was causing the interface on the ISR to have a bunch of overruns and go into a hung state.
Conditions:
When you put a WLAN into VLAN25 the switch sets the rcpPortMap register to 1 for that VLAN. This is fine when a WLAN is still on VLAN25. However, when you change the WLAN to a different VLAN than 25 from the CLI, it is not setting the rcpPortMap back to 0 for VLAN25 and it is causing the replication of the frames. You can see the rcpPortMap setting by running the following commands:
show platform vlan 25 show platform fwd-asic register read register_name AqmRepDestMapTable-25
Workaround:
Workaround #1:
The command below will set the register back to 0 for the VLAN with MVID 7.
show platform fwd-asic register write register_name AqmRepDestMapTable-25 module 0 field rcpPortMap value 0x0
Run this command to verify the setting was applied.
show platform fwd-asic register read register_name AqmRepDestMapTable-25
After doing this, you will see the frame replication stops happening.
Workaround #2:
Reboot the switch. After a reboot, it will initialize the rcpPortMap correctly.
Workaround #3:
Put a WLAN into the VLAN that has the rcpPortMap set incorrectly. Even if the WLAN is shut down, it will not replicate the frames on the wired network anymore.
2015-07-03 02:41XXCTS_SRStatusCE Pending Workaround => Customer Updated
Further Problem Description:
each frame gets multiplied 15 times again causing a storm of DHCPv6 frames
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