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What is Static Mapping?

In DHCP > IPv4 Lease Table > Make Static, and regarding:
DHCP Server
DHCP Range
IPv4 Address

If I set the "IPv4 Address" to a value in the "DHCP Range", Can the "DHCP Server" offer this address to other devices?

Is this correct?
Static Mapping = Always assign an IP Address to specific MAC addresses and Prevent the DHCP Server from assigning it to other devices even if it is in the DHCP Range?


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  • 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.
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  • 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.
Children

  • 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?
  • 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

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA