Client got wrong gateway

Simon Hobson dhcp1 at
Fri Feb 24 08:07:16 UTC 2017

Rui Mao <maorui2k at> wrote:

> I installed a Ubuntu 16.04 and configured isc-dhcp-server 4.3.3 as DHCP/BOOTp server. But the iPXE didn't got correct gateway from it.
> The DHCP server is, and the client is in another VLAN which gateway is
> I captured Ethernet packages by tcpdump, and also used a Windows Server 2012 for comparison. It seems ISC-DHCP-Server sent a wrong gateway.
> Is this a configuration issue or a bug of ISC-DHCP-Server?

It's a configuration issue - and a known "gotcha" !

Move your class statements out of the subnet declarations - regardless of where you define them, they are global in scope (ditto for host statements). So a client can match a class even if you **think** you've defined it only for a specific subnet. When this happens, the client gets options inherited from the class in the other subnet - and a side effect is getting (in this case) the router option from a different subnet.

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