Upgrading from ISC DHCP 3.0.5 to 4.1 or 4.2 appears to break dhcp-overload function

Patrick Trapp ptrapp at nex-tech.com
Mon Mar 10 20:46:49 UTC 2014

We have been running ISC DHCP 3.0.5 and trying to position ourselves for an upgrade to new 'hardware' and a new version of ISC DHCP. When we tried the upgrade, we had to back out because many of the clients failed to get addresses.

Long story short, we found that the server was not overloading the data for DHCPOFFERs that were made to certain networks. For the networks in question, we use option 82 to identify what pool the client's address should come from. It's been working this way for years. If the client making the request is not on a network utilizing option 82 (basically small test networks), the server overloads the DHCPOFFER as expected.

We changed only the server - new virtual server, new operating system, new ISC DHCP and saw it on both 4.1 and 4.2 releases of ISC DHCP. We have been unsuccessful finding documentation explaining the new behavior. My understanding is that overloading is not something that we can turn on, it's something the server handles on its own.

How do we/Can we get the new server to behave like the old one did? Is there a known issue with overloading when option 82 is involved or is that another red herring?

Thanks for taking the time to read the question.

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