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I have a Ethernet printer which should be running behind a Raspi which is connected via WiFi to the rest of the network. Network wise this is working fine, but I have issues with the ISC DHCP server using the following /etc/dhcp/dhcpd.conf:

subnet 10.0.50.0 netmask 255.255.255.224 {
    range 10.0.50.10 10.0.50.15;
}
host printer {
  hardware ethernet aa:bb:cc:dd:ee:ff;
  fixed-address 10.0.50.10;
}

Without the explicit mac address, I still ran into issues where 10.0.50.11 (or others) where assigned to the printer.

Question Is there a better way to ensure that only one - and always the same - IP address is provided by my DHCP?

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  • Put the host inside the subnet scope and do not use a fixed address from the range. Also, you don't have to specify a dynamic range if you don't need to use one.
    – forcefsck
    Mar 18, 2016 at 20:33

1 Answer 1

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As a general rule, I tend to keep ephemeral addresses and fixed addresses separate. For example, I have a basic network using 192.168.0.110-199 for clients, and then everything up to 109 is available for static - including those assigned by DHCP. (The strange numbers here are because I'd already declared that network printers would all get IPs in the 101-109 range.) So the config looks something like this:

subnet 192.168.0.0 netmask 255.255.255.0 {
  range 192.168.0.110 192.168.0.199;
  option routers 192.168.0.10;
  # thresholdrpg.com
  option static-routes 64.253.105.42 192.168.0.11;
}
host yosemite {
   hardware ethernet aa:bb:cc:dd:ee:ff;
   fixed-address 192.168.0.14;
}
host hippo {
   hardware ethernet 00:11:22:33:44:55;
   fixed-address 192.168.0.103;
}

dhcpd is quite happy to give out addresses that aren't in the 'range', though of course still within the subnet. In your case:

subnet 10.0.50.0 netmask 255.255.255.224 {
    range 10.0.50.12 10.0.50.15;
}

There's now no way that any other client will be given .10 or .11; only an explicit "host" block will set that.

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