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DHCP Clients / server do not see each other - 3 NIC environment - SBS 2003

Posted on 2004-09-07
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Last Modified: 2010-03-18
Server is running Microsoft Small Business Server 2003 & I converted from a single NIC to multiple NICs since the initial setup. I have DHCP running & scoped (green arrow), but nothing downstream is seeing the server (or vice versa). Problem is very similar to what was experienced by
http://www.experts-exchange.com/Networking/Microsoft_Network/Q_21087777.html
but I'm hoping to avoid the reinstall.

Current architecture is...

Cayman DSL modem - gateway IP (75.10.200.101, subnet 255.255.255.248) (fictitious address for demo)
(5 static addresses available - DHCP off in Cayman)
Static address range 75.10.200.102-106
Single Cable from Cayman to 5 port switch with cables from there to NIC card A & NIC card B
75.10.200.102 assigned in Windows to NIC card A
75.10.200.103 assigned in Windows to NIC card B
NIC card C assigned static address of 10.0.100.0 - subnet 255.0.0.0
DHCP enabled for domain.local
Cable from NIC card C goes to 8 port switch with network printer and several machines plugged into it.

None of them can ping the server or obtain an IP address from it. I verified the switch worked by pinging the printer's 169.x.x.x APIPA address.

Any Ideas??
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Question by:nchurricane
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Assisted Solution

by:cfairley
cfairley earned 50 total points
ID: 12005476
Is the link speed setting for NIC C set to "auto".  If it is, you can try changing it to a defined setting that is accepted by the switch.  I had an issue yesterday with one of my DHCP servers with multiple NICs.  The switch was set to "auto negotiate the speed" and the NIC was set to "auto" and would not give out addresses through that NIC.
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adamdrayer earned 450 total points
ID: 12006822

your NIC-C has an address of 10.0.100.0, right?  first of all, you should never assign a NIC with an address that ends with 0.  That might be the problem right there.  Second, make sure that the DHCP scope you are serving is in 10.x.x.x, but the server IP is resevered.  DHCP doesn't work if the server and clients are on different subnets.

Now, type "route print" at a command prompt.  It should tell you where it is sending packets destined for 10.x.x.x  The thing to notice is the Interface #.  If it is not routing packets destined for 10.x.x.x, then it's not going to work.  type ipconfig do determine the interface# of nic-C , then type this:
route -p add 10.0.0.0 mask 255.0.0.0 IF <3>
(assuming your NIC-C is labeled as interface 3 when you type ipconfig)
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Author Comment

by:nchurricane
ID: 12007212
Thanks for the quick feedback. I had the same problem with x.x.x.1 addresses (as I did with the 10.0.100.0) so I don't think that's it & I reset the scope to match the range each time I tried a different IP for the Server Local Connection.

It does look like may be a routing issue, but I've changed the config to get my users back up and may have already blown that away in the process. I will try some of this in a test environment when I get a chance.

In the meantime, do you see any fundamental security or other flaws with this workaround design...
Turn off SBS 2003 DHCP Server

Use 3 of static IPs as follows:
1 - SBS 2003 server for Web Site (NIC A)
2 - SBS 2003 server for Remote Access/VPN/Intranet (NIC B)
3 - NAT DHCP Router to switch with all LAN machines/printers  - Connect NIC C to obtain IP address from router (so that local machines can access server resources)

Thanks
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Author Comment

by:nchurricane
ID: 12013181
To those who may follow...It turns out that there were two intermittent shorts in my patch panel that were the cause of both communication difficulties & slow internet access. It finally failed completely this morning (making it easier to find). While I haven't had the chance to retest the DHCP server yet, I suspect that was the ultimate cause of the failure.
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Expert Comment

by:adamdrayer
ID: 12013185
wow.  that's great you figured it out.  Sorry I couldn't help you troubleshoot it more.  Thanks for the points.
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Expert Comment

by:cfairley
ID: 12014760
Ditto!
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