DHCP Relay Agent - Bad Checksum going out

[Gero Palacio]

Hi Everybody!

I'm currently designing a network and I would like to have a pair of DHCP
servers in failover mode, with relay agents in each subnet to retransmit
the DHCP messages.

*Setup*

* Version "4.2.4-7ubuntu12" of isc-dhcp-server, isc-dhcp-client &
isc-dhcp-relay
* Linux Mint 17
* Network emulated using CORE emulator
<http://www.nrl.navy.mil/itd/ncs/products/core> v4.6.

*Problem*

When a host sends a DHCP discovery, the message goes out the host's
interface with the correct checksum. But, when it's retransmitted by the
relay agent, the checksum is wrong. This means the DHCP server discards the
request and the host does not get an IP address. I found there's a similar
problem when using KVM for visualization (bug #930962
<https://bugs.launchpad.net/ubuntu/+source/isc-dhcp/+bug/930962>) but CORE
emulator uses Linux Containers and, as far as I understand, this should not
be a problem.

I know that a temporary solution would be deactivate checksum offloading,
but I don't feel comfortable with that solution and right now I don't have
the hardware to test it on a real environment.

Has anybody had a similar problem? Should updating to version 4.2.8 solve
this issue?

Thanks all for your help!
Have a good one,
Geronimo.
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