Cisco ASA DHCP Reservation (Solved)

KB ID 0001751

Problem

We have been asking for this for years! Even on my home network I’ve not been able to allocate an ASA DHCP reservation for my laptop and my MyCloud drive. I’ve been in discussions in forums with people who are convinced that putting a static ARP entry into the ASA would solve the problem (it doesn’t – I tested it extensively!)

ASA DHCP Reservation

But finally in version 9.13(1) we can now add a static DHCP reservation (MAC address to IP address).

ASA Static Reservation Confirmation

Create an ASA DHCP Reservation

Assuming you have DHCP already setup e.g.

!
dhcpd address 10.254.254.10-10.254.254.75 inside
dhcpd enable inside
!

Then simply add the reservation, you need to specify the MAC address as xxxx.xxxx.xxxx (that’s with full stops not colons), if in doubt, ping the existing IP address then execute a ‘show arp’ command to show you all the MAC addresses the firewall can see, so you can copy/paste it into the following command;

dhcpd reserve-address 10.254.254.50 38f9.d326.66cc inside

Quite why it took so long for Cisco to give us this basic function, I have no idea.

Related Articles, References, Credits, or External Links

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Author: PeteLong

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6 Comments

  1. what verson of ASA software you are running ? I do not see reserve-addresss syntax available.

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  2. This did work, but maybe it was 9.14 or 9.16 that this seems to have broken. My reservations don’t work anymore. Is anyone else seeing this?

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    • Upgraded to 9.16(3) and still have issues with DHCP reservations. All are in correctly and it is unreliable. Had to create my own DHCP server.

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      • The dhcp reservation issue should be fixed in 9.16(4)
        At least the release notes list CSCwb54791 as resolved.

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  3. I had a problem with the reserved address not being assigned, and the “workaround” from cisco support was to configure a static arp entry for the host, *in addition* to the dhcp reservation. After a couple of “clear dhcpd bind” and “clear arp” runs, the host eventually got the reserved address. Clunky, but that’s the nature of bugs.

    It may be related to
    https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwb54791

    Which cisco claims was fixed in ver. 9.18(1). Who knows….

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