How are DHCP addresses selected?

[Tom_Hall]

Hi - I have an ASUS RT-AC87U, running Merlin 378.53.
I only have a few devices, so I set my DHCP pool to start at 192.168.1.100, and I have left the Lease Time unchanged at 86400

I was expecting therefore to see my devices get IP addresses in the low .100's, but I'm seeing that some of my devices are getting .200 addresses eg. my Galaxy S4 mobile is 192.168.1.227

So, the question is: how are the DHCP addresses selected ?
It doesn't look like its Sequential - is it Random?

-Tom

 

[GSpock]

Hi,
I noticed something similar: my ip range is 192.168.20-50 and any new devices get systematically something above the range ..... randomly, apparently .....
GS
P.S. running Merlin 378.53

 

[mstombs]

See the dnsmasq documentation - candidate IP addresses are computed using a hash function on the device MAC address, this means the allocated IP address is 'sticky' and same devices tend to get same address even when not fixed as 'static'. dnsmasq will check IP address not in use or reserved before issuing. This process helps avoid problems if devices hibernate or go away then come back and try to reclaim the same IP address leading to conflicts.

There is a bug somewhere if auto allocated devices are not within the configured range - but static configured devices do not have to be.

 

[CooCooCaChoo]

DHCP addresses are assigned by calculation based on the NIC's MAC address unless statically assigned.