[Dnsmasq-discuss] dnsmasq - dhcp unicast or multicast

[Simon Röblreiter]

Hello, dnsmasq-community!


I ran into a strange situation today.
I was configuring a virtual mikrotik router (routerOS)
to request a specific IP from my provider.

I did a series of tests in my local network.
When I checked the traces I was capturing, I noticed,
that routerOS was sending multiple dhcp-discover packets
in a burst-like manner and dnsmasq responded multiple times.
I suggest that is intended behaviour in order to ensure
the fastest possible completion of the handshake.

What puzzled me, was the fact, that each frame of the
communication was a broadcast.
Shouldn't each device send unicast frames as soon as
it knows the mac-address of the other device?

To be able to compare against something, i also traced
the dhcp-handshake of my smartphone (Galaxy S2 / cyanogenmod13)
to the same server.

You can view screenshots of the two traces through the following link:
(I wanted to attach them to the mail, but there's a size limit of 40KB.
@mod: Sorry for the repost. Didn't know that.)

https://www.gasslfeld.at/showcase/dnsmasq/

The cyanogenmod-handshake is doubled because I switched
the wifi on and off two times.
Both traces were captured with tshark directly on the machine
running dnsmasq (OS=ubilinux).

Any suggestions?


Thanks in advance!
Simon Röblreiter