problem with DHCP and sysadmin

in Mac Software edited January 2014
Hi All,

OK, a quick question....I am at a major University, and the sysadmin has a strong dislike of Macs (I had to fight just to get t allowed on the network).

The problem is this - he claims that the Mac, in both OS 9 and OS X versions, "steals" IP addresses from other machines using DHCP. He also claims that this can and does happen even when the mac is not rebooting, but I would like to ignore that part of his claim for the moment, because that seems patently absurd.

So my question is this - DOES OS X behave badly on Windows-run DHCP servers? Please, I am NOT looking for "that guy is a jerk" etc, but am not saavy enough to know the particulars of DHCP networking in its various flavors (someone told me that this would not be a problem if the sysadmin either used a *nix box as the DHCP server or properly configured his Windows DHCP server, but my root question is simply IS this possible?)




  • Reply 1 of 3
    addisonaddison Posts: 1,185member
    If you are allocated a static ip address just use that. If not the DHCP server should not allocate an ip address that is already in use. Macs do renew their ip addresses peridocally, but on my network thay are always reallocated the same ip number, I don't know why. This should not effect other machines as I said it should allocate an ip address that is being used by another machine.
  • Reply 2 of 3
    gargoylegargoyle Posts: 660member
    taken direct from my MCSE course module that I did last week.

    By default, a dhcp client (your mac and the PC's) will shout for a dhcp server. The server will answer and say here I am, you can have this address. (Note, more than one DHCP server can answer at this time) The client then picks one, and tells that dhcp server I'd like this one. If no one else stole that address in the mean time (a few milliseconds) then the server sends you an acknowledgement. Your client sets up your TCP/IP with the info, and the server tags the address as being used.

    It is upto the server to keep track of used addresses.

    Renewals. Normally the default lease time for addresses given by a DHCP server is 8 days. After 4 days your client will ask for a renew. If successful, you go back upto the full 8 days. This is why if you use the network regularly, you will normally keep the same address.

    If you have not been able to contact the original DHCP server for a renew at 7 days, then your client tries a new broadcast to any server.

    At exactly 8 days, if you have not been able to contact any DHCP servers, your client should stop using the address immediately.

    Although this info I got specifically from a MS course, I think it applies to any DHCP client / server setup as its all based on the same standards.

    Hope this helps.
  • Reply 3 of 3
    scottscott Posts: 7,431member
    Not that it helps much but I use my Mac with DHCP at work (peecee shithole) and have no problems. One of the IS people thought my mac was the rouge computer on the network but a quick check of the IP showed it wasn't me.
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