DHCP Relay Issues With Microsoft Surface Pro Docks and Junos
After deploying some new Juniper EX4600 core switches, my customer complained that he was experiencing about 45 seconds of delay in getting an IP address on a Surface Pro connected to a dock. The second time of connecting, it took about 8 seconds which was more acceptable. The 45 second delay came back every time they moved the Surface Pro to a new dock.
After ruling out a few things like Spanning Tree and LLDP, we isolated it down to the core switch. An older core switch elsewhere was configured for BootP Helper rather than DHCP relay, and clients connected to that did not have the problem.
Other devices didn’t exhibit the problem either – a Macbook was given an IP in the region of 4 seconds after connecting. The Surface Pro took 8 seconds consistently to connect when using a USB dongle. So the issue seemed to centre around the dock.
If you haven’t seen one of these before, they look like this – a black brick with some ports on it, supplied with power by another black brick:

The wire to the right of the image above ends in an edge connector that is plugged on to the Continue reading




