[Dnsmasq-discuss] Issue with circuit-id matching on dhcp requests

[Simon Kelley]

The very first step is to set the --log-dhcp option and look at the 
logs, that should give you clues as to what is happening and more 
information to supply here if it doesn't make sense to you.

Cheers,

Simon.

On 10.05.2026 10:25, Max Boon wrote:
> Hello,
> 
> I have a bunch of switches that have previously been supplied with IP 
> addresses using isc-dhcpd that I am now replacing with dnsmasq. There is 
> an address range for automatically assigned IP's and the rest with 
> static host assignments, all in the same /24 subnet.
> 
> The static assignments are assigned using option 82 circuit-id to set a 
> tag which is then matched in the dhcp-host declaration. For the most 
> part I have managed to get it working, but I have noticed something in 
> my logs which I am not sure is a bug or just my general lack of 
> understanding...
> 
> Basically, if a DHCP inform packet comes in, the circuit-id gets 
> matched, and a corresponding ack gets sent by the server. However, if a 
> DHCP request comes in, the server doesn't seem to be able to match the 
> circuit ID at all and responds with "/dnsmasq-dhcp[5631]: no address 
> range available for DHCP request via eth0/*"*
> 
> I have confirmed using tshark that the incoming DHCP request packet 
> contains a circuit-id that matches an assigned dhcp-host entry.
> 
> My dnsmasq.conf has only the following range:
> 
> dhcp-range=172.16.127.16,172.16.127.49,255.255.255.0,12h
> 
> I have a seperate .conf containing the static entries, repeated like so:
> 
> dhcp-circuitid=set:lag_103_1309_91,lag-103:1309.91
> dhcp-host=net:lag_103_1309_91,172.16.127.141,Switch1
> dhcp-option=net:lag_103_1309_91,12,Switch1
> 
> dhcp-circuitid=set:lag_104_1408_93,lag-104:1408.93
> dhcp-host=net:lag_104_1408_93,172.16.127.139,Switch2
> dhcp-option=net:lag_104_1408_93,12,Switch1
> 
> Best Regards,
> 
> Max
> 
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