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Multiple DHCP Servers and access

Posted on 2008-06-16
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Last Modified: 2012-08-14
we have multiple dhcp servers in our 2003 org, each backing up the other with exemptions. Occasionianlly a PC will grab an IP from our DHCP server on the other side the ocean, the scopes are identical but something is different, the PC can not access certain internal sites or servers.

our current work around is to restart the DHCP client service on the impacted workstations
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Question by:kf4ape
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by:grahammj
ID: 21796556
DHCP, by itself, can't be routed.  You could turn off your IP Helper address in your router configurations from those sites.

It can't access the local sites because I'm guessing the DNS servers are different between sites (that and/(or) the default gateway is different between sites).  
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by:kf4ape
ID: 21796579
the scopes are identical and if we turn off the IP Helper we loose our redunecy
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by:KCTS
ID: 21798513
The normal method is to use a split scope with the local server having 80% of the available leases and the remote server the other 20%. When a client requests a DHCP it does so via a broadcast, all DCHP servers that see the broadcast will offer an IP, the client will accept the first one to be offered. Normally this will be the closest DHCP server as it responds first. If the local DCHP server is busy then occasionally the remote DHCP server may get in first - this is to be expected and is the way in which DHCP works - You cannot to this any other way.
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by:kf4ape
ID: 21798850
KCTS,
I understand DHCP and how it works, and the 20/80 is not the prob...I could care less which server gives the IP...the prob is when the one that is across the ocean gives an IP, all the sudden it can not access servers, websites yet the scopes are identical...both are 2003 boxes
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by:ChiefIT
ID: 21819847
That's probably because the preferred DNS servers, that are handed down by your DHCP config, are not reachable by that client. Look at the client's ipconfig /all and see what the "preferred DNS servers" are for that client when this happens. If they are your overseas site's DNS servers, you know that is passed down from DHCP config on your overseas servers.

Have you thought about disabling the ability to tunnel DHCP to and from your overseas site?

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kf4ape earned 0 total points
ID: 21832230
ChiefIT - the scopes on both side of the pond are configured identical...we found out yesterday after calling MS, dell and OEM drivers arent the same for w2k boxes...
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