I happen to experience some strange behaviour.
Last week I bought an HP printer, with ethernet port.
When I connect the printer to any port of my RB2011 (tried multiple cables and upgraded to ROS 6.35.2 during testing) the printer will not receive an IP from my DHCP server. Also when I configure an IP address manually, the printer is unreachable.
I also have a mAP. I configured both ethernet interfaces of this mAP and the wireless as member of the same bridge and locked the wireless interface as station to my RB2011 wireless AP.
Then my printer does receive an IP address, and also the static configured IP is functional.
Does anybody have an explanation for this?

{added info}
What I see happening is that the DHCP server (running on my RB2011) is offering an IP address, but nothing happens.
When the mAP is in between, the offer is turned into bound almost instantaneously.

PS. my mAP is running 6.34.4, for that matter.

Is your ethernet port in the bridge or slave port member where your dhcp server is ?

Are all ethernet ports set to auto configuration?

@darkprocess:
Yes, all are member of the same bridge.

@pe1chl:
All set to auto.

I thought it could be related to gbit capable interfaces, since the mAP only has fast ethernet ports. I only tested the gbit interfaces of the RB2011.

And when you connect the printer to the RB2011 in the non-working state, what does the ethernet interface info
tell about the negotiation result?
Also try to put the printer on a 100 Mbit port when it fails to negotiate on the gigabit ports.

If I connect the printer to a 100Mbit port, it works!
When connecting to a Gbit port, the Routerboard stated the negotiation was done and speed is set to 100 Mbit.
That is ok, since the printer doesn't have a Gbit interface. I couldn't find any setting in the printer to force to any speed, but forcing the Routerboard to 100Mbit didn't change a thing. Also disabling the advertisement of Gbit makes no difference.
I have another Routerboard with Gbit interfaces that I will try (RB750GL).
Keep you posted!

Just my $0.02's worth here - if the printer only has a 10/100 interface on it, why waste a gigabit port of the 2011 if the 10/100 ports work well?
(I mean, I agree that it should be possible to connect the printer to whatever port you like, and the 2011 shouldn't be so finnicky, but if you have plenty of available ports..... )

Side note here - it seems like the gigabit ports in devices like the 2011 and the 1100AH commonly have issues connecting to certain devices. It was common to have the cablemodem / dsl modem / cisco switch connected to ether6 as wan, for instance.