DHCP server: have static IP on one subnet, dynamic IP on another subnet

RouterOS General
1

I have the following configuration:

/interface set [ find default-name=ether1 ] name="wan"
/interface set [ find default-name=ether7 ] name="physical-lan"

/interface bridge add name=lan
/interface bridge port add bridge=lan interface=physical-lan
/interface bridge port add bridge=lan interface=ether2
/interface bridge port add bridge=lan interface=ether3
/interface bridge port add bridge=lan interface=ether4
/interface bridge port add bridge=lan interface=ether5
/interface bridge port add bridge=lan interface=ether6
/interface bridge port add bridge=lan interface=combo1

/ip address add address=192.168.1.254/24 interface=lan network=192.168.1.0

/interface vlan add interface=physical-lan name=wifi-guest vlan-id=200
/ip address add address=192.168.200.254/24 interface=wifi-guest

/ip dhcp-server config set store-leases-disk 24h
/ip pool add name=dhcp-lan ranges=192.168.1.50-192.168.1.150
/ip pool add name=dhcp-wifi-guest ranges=192.168.200.50-192.168.200.150

/ip dhcp-server add address-pool=dhcp-lan disabled=no interface=lan name=dhcp-lan lease-time=1h
/ip dhcp-server add address-pool=dhcp-wifi-guest disabled=no interface=wifi-guest name=dhcp-wifi-guest lease-time=1h
    
/ip dhcp-server network add address=192.168.1.0/24 netmask=24 gateway=192.168.1.254 dns-server=192.168.1.254 domain=lan
/ip dhcp-server network add address=192.168.200.0/24 netmask=24 gateway=192.168.200.254 dns-server=192.168.200.254 domain=lan

I also have a static lease for a laptop on dhcp-lan:

/ip dhcp-server lease add address=192.168.1.1   mac-address=<redacted> comment="laptop"

That all works fine. Laptop can get on the lan using a wifi connection and gets the 1.1 static IP. Guest devices can get on wifi-guest, and they are assigned a 200 dynamic IP. However, when laptop gets on wifi-guest (using wifi so same MAC address as when on lan), it cannot get a 200 address. It hangs for a while and then is eventually assigned 192.168.1.1, which can’t do anything on wifi-guest. Why doesn’t it assign a 200 address when laptop gets on wifi-guest?

2

on the lease you have to restrict the assignment to the (1.x) specific dhcp instance, now I don’t remember by hart the command .. but you’ll find easily

3

I haven’t found anything in the docs that indicate you can do that.

4

Make sure this is set to the name of your DHCP server instance for the subnet that the address is on - ‘dhcp-lan’ in your case - so that

/ip dhcp-server lease add address=192.168.1.1 mac-address=<redacted> comment="laptop"

becomes

/ip dhcp-server lease add address=192.168.1.1 mac-address=<redacted> comment="laptop" server=dhcp-lan

That way the router won’t try to hand out the reserved address unless the DHCP request comes in on the correct server/interface.

5

ok, exactly as @aholmes says :smiley:

6

That’s what I get for reading the documentation instead of looking at the GUI (I’m doing my config in a script). The docs have the “server” property listed as read only. Anyway, I added it and all is well. Thanks!