dhcp relay from multiple switches

Mark Starling Mark.Starling at oa.com.au
Tue Jul 11 23:45:27 UTC 2017

It is not NAKing due to being authoritative. It is NAKing because it has an active lease for IP address 1 given to device Y switch 1 port 6 and gets a DHCPREQUEST for IP address 1 from device Y on switch 2 port 26. So device details don't match the lease. This is reasonable behaviour, I just wish there was a way to stop it.

Anyway I have a workaround. My DHCP server is given multiple IP addresses on the same interface and each switch relays to a different address. Then I run multiple instances of dhcpd each listening to a different address and with pools only for 1 switch (non authoritative). Works reliably so I'm happy.

For any Googlers, you need to configure a unique pid and lease file for each instance and in my case disable apparmour for dhcpd (this is an apparmour bug in ubuntu 16.04).

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