IP Helper Mystery
Posted: 24 Jan 2014 05:47
Hi,
I have an OmiSwitch 6850 set up as the Core Layer 3 switch. It has an IP Helper configured to send DHCP requests from VLAN 200 (Clients) to VLAN 100 (Infrastructure).
Everything works fine except with one type of device, a Meraki access point. The switch does not appear to pass the DHCP Discover Request through to the DHCP Server.
I've confirmed with Wireshark that the DHCP Discover frame is never passed to the DHCP server although it works for every other laptop, desktop, thin client... The only difference I can see between the DHCP Requests is the size of the frame. A Meraki seems to have a 346 byte frame, while every other device has the standard 342. See attached.
Anyone have any idea what could be causing this? Could the switch be dropping the frame due to the larger size? I assume the switch knows it's a DHCP frame based on the source/destination UDP port numbers and not the frame size.
Meraki Capture: HP/Dell Capture: Thanks for any help.
I have an OmiSwitch 6850 set up as the Core Layer 3 switch. It has an IP Helper configured to send DHCP requests from VLAN 200 (Clients) to VLAN 100 (Infrastructure).
Everything works fine except with one type of device, a Meraki access point. The switch does not appear to pass the DHCP Discover Request through to the DHCP Server.
I've confirmed with Wireshark that the DHCP Discover frame is never passed to the DHCP server although it works for every other laptop, desktop, thin client... The only difference I can see between the DHCP Requests is the size of the frame. A Meraki seems to have a 346 byte frame, while every other device has the standard 342. See attached.
Anyone have any idea what could be causing this? Could the switch be dropping the frame due to the larger size? I assume the switch knows it's a DHCP frame based on the source/destination UDP port numbers and not the frame size.
Meraki Capture: HP/Dell Capture: Thanks for any help.
