By nwagbostella ·
I have a dlink DIR 615 rouer which i have been using on company network of over 50 computers. Recently all the computers on dhcp disconnected from the database server without warning, on checking the systems i found out that none of the dhcp computers could see each other or server. Only the those on static could do that. They can still connect to the internet but cannot print or work on network. I have reset the router but the problem persists. Please help me.


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So to clarify

by robo_dev In reply to NETWORK PROBLEM

when it fails, those PCs on DHCP:

have a valid address, mask, and gateway?
cannot ping the router?
cannot ping each other?

IS the database server on the same network as these PCs and router?

if so, then the router and/or DHCP server is not a real point of failure for the system.

What sort of Ethernet switches are used for these PCs?

How are the switches connected to each other?

Is there any chance a rogue DHCP server has been installed, such as a WLAN access point?

Not being able to print or work on the LAN sounds like a broadcast storm. Microsoft SMB protocol is a broadcast-based protocol, and a network error condition (e.g. topology loop, misconfigured switch, failing adapter) can cause a storm condition.

I would get an Ethernet hub and install the WireShark tool on a laptop...this can let you capture and analyze what's going on on the LAN.

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maybe theres another DHCP server online?

by markp24 In reply to NETWORK PROBLEM

Whats the ip address of the systems that are supposed to be using dhcp, (when you do an ipconfig on them what do you get for dhcp server and gateway address, are they correct?

basically i have the same ideas as robodev.

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Network Problem

by nwagbostella In reply to NETWORK PROBLEM

There is anotner dhcp server on the network, dlink wlan AP whose dhcp systems are see themselves as well as static systems. Yes the database server is on the same network but on static ip while others who cannot see each other are on dhcp.
The ips for both static and dhcp systems are correct. But while the static systems can see themselves the dhcp cannot. These systems are connected to three different 24ports switches which are looped together in a star topology.

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Do you run a domian?

by Spitfire_Sysop In reply to NETWORK PROBLEM

Usually if you run a windows domain you want the DC to be the only one broadcasting DHCP. So you would turn off DHCP on all routers and APs so you could control all of the IP addressing in one place on your server.

In order to ping the DHCP server from a computer that is set to get it's IP address automatically you could configure it with static data just to test connectivity and then try to pull the settings again by switching it back to automatic.

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What have you done already?

by ThatITGuyTy In reply to NETWORK PROBLEM

I'm interested in what you have done already to remedy the problem. Have you deduced the issue to your router or another connectivity device? What routing protocol are you using on your network? Is the speed on your links to your router and switches the same or set to autonegotiate? Do you have or did you recently implement VLANs or ACLs on your network?

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Solve the problem one step at a time

by jrussell_75423 In reply to NETWORK PROBLEM

If nobody is hitting the server you have nothing to lose by borrowing it's network connection for a second or two. Pull that network cable and hang your laptop or similar there that has a fixed IP. Can you hit that from otjer locations? If so, you know the hardware is not wonky. Now, set the server to a fixed IP. Everybody should be able to find it once the routers have learned the path, and youll always know at least one way to make the boss happy and make things work through the business day.

Like the other folks, I strongly suggest you only have one router handing out addresses. If the whole network is on one subnet ... you can make this happen by adding everything back to the network one item at a time. as you do this, using DHCP, let the router in the middle at the server hand out the addresses, but before you leave, go in and change the address on the machine from DHCP to fixed, using whatever address the router gave out as you know that address is valid. 50 machines is a lot, but not unachievable. By the time youre halfway through youll see the way its going, and likely be able to put the address scheme together foryourserlf. And verify that whatever hidden items -like the boss' buffalo - are on the appropriate subnet.

Yes it is a lot of work but it will solve a lot of problems now before they get worse. And with a good network map now solidly in your drawer you can always find a way to help the boss hit the server - and it's always all about the money, so he will be happier with that than with NObody hitting it... it's a patch, but it works.

Get off the DHCP for small networks. Clean up the tables. Use good subnet schemes. Keep your antivirus running. Stop sneakernet problems. Monitor your incoiong logs.

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