Regarding dhcp server behavior

Eugene Grosbein eugen at
Sat Mar 23 10:01:01 UTC 2019

23.03.2019 16:41, Shweta Jogi wrote:

> What can be the reason behind such behavior?

When DHCP relay forwards original broadcast of DHCP client to DHCP server,
it modifies the request makeing it unicase and relay additionally inserts
one of its own IP addresses into the request with special DHCP attribute.

DHCP server processes request only if that IP of relay is "known" to the server,
e.g. the IP belongs to one of networks that the server must serve.
So, DHCP server will not process requests from arbitrary DHCP relay.

Just include network containing that IP of the relay to configuration of DHCP server:

subnet X.X.X.X netmask Y.Y.Y.Y {}

Then server needs not "listen" for broadcasts on extra interfaces.

This way you can even run DHCP server not listening on any interfaces at all,
if all requests go through relays only.

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