[Dnsmasq-discuss] Netboot drops DNSMasq DHCP offer

Conrad Kostecki ck+dnsmasq at bl4ckb0x.de
Thu Apr 4 18:42:17 BST 2019


Hi Simon,

Am 04.04.2019 16:10:32, "Simon Kelley" <simon at thekelleys.org.uk> 
schrieb:

>How are you producing the dnsmasq captures? on the host running dnsmasq,
>or elsewhere on the network?

Both captures were produced on that machine, which runs the DHCP server.
This means, on the non working setup, this is my linux router.
The fritzbox also does offer a capture on its interfaces itself.

Captures where done with tcpdump on port 67+68.

>The DHCP is asking for, and getting, broadcast replies (ie to
>255.255.255.255) It's just possible that : 1) no other DHCP clients
>you've used ask for this
What do you mean by this? Sorry, but I didn't understand this.

>  2) the firewall configuration on the host
>running dnsmasq blocks packets with destination 255.255.255.255.
I can rule this out. If I take the same network cable, which I used for 
Netboot, but instead, connect my modern ThinkPad X260, DHCP works just 
perfectly fine.
I did also give now a try and connected directly the Netboot machine to 
an interface directly on the machine, which hosts DNSMasq.
So I think, I can rule out at least the hardware side here.

Conrad




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