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Static DHCP 2 MAC address fields

Discussion in 'Tomato Firmware' started by gijs73, Feb 24, 2010.

  1. gijs73

    gijs73 LI Guru Member

    Hi guys,

    I have noticed an issue with my tomato instillation.
    I am using 1.27

    When i try and set a static dhcp address i am given two fields to enter the MAC address

    If i try to make a static address by clicking the 'static' link on the device list the mac address is filled into the top mac address field leaving the bottom one full of 0's

    The static addresses work however i am pretty sure the second mac address field is not supposed to be there.

    I have tried re installing version 1.27, thorough NVRAM erase and holding in the reset button for a few seconds and then installing 1.27 however the second field remains.

    Here is a screenshot of what i am talking about
    Any ideas would be appreciated.

  2. Toastman

    Toastman Super Moderator Staff Member Member

    This is a new feature. It allows you to allocate, for instance, the same IP to both the LAN and Wireless card of a particular computer, depending which one is in use. Just ignore the second one if you don't have a use for it.
  3. gijs73

    gijs73 LI Guru Member

    Thanks for that Toastman, here i was thinking something had broken.

    I checked the changelog and didnt see any mention so thought it must have been something my end :doh:

    It is a good idea though :)

    Thanks again
  4. RonV

    RonV Network Guru Member

    Has anyone been able to get this feature to work? I have a Dell laptop D830 and set up Windows 7 and Dell's utilty to power off wireless when the ethernet port is plugged in. When I do this the ethernet port does configure with the DHCP configuration.

    I haven't pulled the logs yet on the router but I will update the post tonight when I try again.
  5. fineghal

    fineghal LI Guru Member

    When you're setting the static IP in tomato, you're simply reserving the given address for the given client.

    If you were to bring your connection up/down 100 times, it would always be given the same IP.

    This is useful because: DHCP is the default for pretty much everything, and you can assign a hostname for the machine to respond to. Glenda-lap.lan is much easier to remember than her static IP or having to look it up every time.

    Not being into Networking, I believe that you could set static IP and appropriate gateway/mask/dns etc. from the client, and assuming the router has DHCP running, the router will give you the requested IP. if it is not in use. I'm not really sure what would happen if you requested an IP that was in use, or an IP outside the router's own subnet.

    IE: Router DHCP range is, static IP request from client is

    Anyway, hope that helps a little bit.
  6. RonV

    RonV Network Guru Member

    Thanks for the reponse...yes I am well versed in the usage of static DHCP but my real issue is the the two fields for MAC values. If I put both the Ethernet port's MAC and the Wireless Adapter's MAC into the static DHCP configuration screen it should allow on or the other to have the same IP address depending on which is active.

    What I am finding out is say the wireless connect and gets the IP address for the lease time. Then when you dock the laptop and eithernet port goes active which disables the wireless. When this hapens the eithernet card does not get an IP address from the router. Windows 7 assignes it one of those generic safe addresses.

    I theory is that when the ethernet adapter goes active it bids for the DHCP address before the wireless has released it and the DHCP server on the router refueses the bid for the address.


    I was correct in my assumption. For some reason even in the wireless adapter goes disabled Windows 7 holds the address and when the bid comes back Windows 7 rejects it from the DHCP server:

    Address 192.168.xx.xx being plumbed for adapter 11 already exists

    Also there is a couple of posts on MS and another blog that talks about this:


    I guess I am SOL when trying to leverage this dual mac configuration :-(
  7. Toastman

    Toastman Super Moderator Staff Member Member

    Simple answer - don't use this "feature". It's a mess.

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