Cisco Switching - Issues with distribution switches during a core switch outage
Posted on 2013-06-20
I have (2) Cisco 3750 switches in a stack configuration functioning as a CORE switch. The configuration of these switches have about 10 VLAN's on them, and layer 3 routing is enabled with the switches functioning as the default gateway for devices on all VLANs.
I have about 18 switches uplinking to these core switches (Cisco 3560G switches) using a 2 port etherchannel link for each uplink with 1 port going to 1 switch in the stack, and the other port going to the 2nd switch in the stack. This was to maximize redundancy should one of the core switches in the stack go down.
The core is setup as a VTP server, with all other switches as VTP clients. VTP Pruning is ON. VTP version is (1).
I recently had an issue where one of the switches in the core stack completely went down (NO POWER). When this happened, everything should have gone from (2) links in the etherchannel group to (1) and everything should have continued. This DID happen, but when everything came back up, some switches did not negotiate their etherchannel link correctly and all connectivity was lost until we removed (1) of the (2) etherchannel uplinks or rebooted the switch (the distribution switch, not the core).
What could the issue be here? I'm able to reproduce this as well if we intentionally take on of the core stacked switches offline.
What does everyone think?