DHCP Discover Failure in a Port-Channel

1. Introduction

Yesterday we stumbled over an absolutely curious phenomenon in association with the DHCP
process and a port-channel. With a port-channel the DHCP discovery process fails.
Our network design is like cisco enterprise environment commended. There are an
access-layer -> distribution layer -> core layer (in direction to the core).
Everything works fine from the beginning from SW1 and SW2. DHCP discovery is
no problem and works fine. On switch 1-3 we have dhcp snooping operational.
The dhcp snooping trust settings are set to the uplinks and respectively to the port-channels.

Continue Reading →