PXE boot failing within VLAN's

Unanswered Question
Oct 7th, 2009

Hi all.

Strange issue with PXE boot.


3750 Series running (C3750-IPSERVICESK9-M), Version 12.2(50)SE3.


VLAN1 = High school data

VLAN208 = Middle school data

VLAN209 = Elem school data

IP helpers for both PXE server and DHCP server in all vlans with PIM enabled.

IP routing is enabled.

Switches in Mid/Elem buildings are Cisco 2960G-24 and 48's with Portfast enabled.

PXE server is on vlan 1 (High School)


If we are connected to vlan 1 in High school or assign a port to vlan 1 in other buildings, PXE boot works with all our models of dell desktops, 170L, GX750, 760's.


If we are connected to VLAN 208 or 209 in other buildings, DHCP info is receive but, fails to find server with all PC's and nothing is registered in the PXE server log. WAIT FOR IT!! for the exception of the Dell Optiplex 760 series. Those work flawlessly in any port, on any 2960G switch, in any VLAN.

So, One points to a problem with the VLAN's but, the Dell 760's seem to point to a PC problem.


I have this problem too.
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iyde Thu, 10/08/2009 - 08:18


Strange, yes.

I see that you have tried to configure VLAN 208 and 209 on ports directly on the 3750. Do you also have the problem if you connect a PC directly to those test ports?

As for the links to other buildings (g1/0/25 and g1/0/26, respectively) I see that they are not configured alike. One has VLAN 209 as native VLAN and runs as trunk. The other has VLAN 208 as access VLAN but is set up as trunk - this link is then trunking with VLAN 1 as native VLAN and the access VLAN config is ignored. Not sure that it has anything to do with your problem but as it looks a little peculiar I just thought I'd mention it.

Also, I see a lot of secondary networks on VLAN208 - I would suggest to split them up in more separate VLANs.


Michael Sales Thu, 10/08/2009 - 08:29


Unfortunately, the person who installed the vlan 208 was not thinking straight. I plan on getting back there during a school downtime to set 208 as Native trunk, do it right, and remove those secondary's. Those ranges aren't used anymore anyway. otherwise, we have tested with ports assigned on 1, 208, and 209 at the core and still the same outcome.

I'm still trying to figure out why the PC's pickup multiple gateway IP addresses. There are at least 2 gateways with the switch IP addresses being one or two of them, then the correct gateway is listed last.


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