What is Static Mapping?

Hi jalil,

That is correct. A statically mapped IP in the DHCP server can be assigned to another client. Best practice is to assign the IP outside of the regular DHCP range and it will map correctly.

Bit different from the Windows Server implementation I normally work with where a 'reservation' is assigned to an IP/MAC pair and the IP is removed from the rest of the DHCP pool.

A statically mapped IP in the DHCP server can be assigned to another client. Best practice is to assign the IP outside of the regular DHCP range and it will map correctly.

So why select the DHCP Server and Range when creating a static map?

Because the DHCP server hands out the IP adresses for the static mappings.

Because the DHCP server hands out the IP adresses for the static mappings.

For what purpose, can't Static Mapping work without DHCP?

No. Static Mapping is intended to allow DHCP clients to always get the same IP each time they request a renewal of their IP. If you want to assign a static IP to a device without DHCP, you have to configure the device itself to use a static IP address.

Example is something like a network enabled projection screen that moves between offices. Because it floats, it has to have DHCP enabled, but because the software at each office has a hard coded IP, the projector has to always get the same IP at each office. A static mapping at each office allows the projector to get the same IP each time it's at a specific office. Otherwise you'd have to teach the end user how to program the static IP into the device at each office, there's bound to be a mix-up somewhere and the inevitable support call. Leave DHCP on but statically mapped. Saves everyone some headaches.

When placing Sophos firewalls to replace non-Sophos firewalls, duplicating Static Mapping is an issue. Creating entries for static maps to already existing DHCP reservations  pop-ups an error stating only addresses within the DHCP Pool will be allowed. A work-around was "Make Static" within DHCP Lease table. But that creates havoc with devices acquiring new IP Address.

How could that be addressed?

Unlike Windows DHCP server, the one in the UTM does not use "Reservations."  In the UTM, you must be careful to assign fixed IPs outside the range of IPs assigned by DHCP.  Does that answer your question?

Cheers - Bob