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IP address woes...

By rob_annable ·
Hi everyone, I am desktop support for a small company in the UK. I ahve noticed that when turning machines on that havent been on for a few weeks the IP addresses get snaffled by other machines and the status is "limited or no connectivity". This isnt just on one machine by the way it has happened lots fo times...
I have tried doing ipconfig /release and renew as well as rebooting the machine several times, tried repairing the connection by right clicking on it and choosing "repair" and also ipconfig /flushdns as well as doing a gpupdate /force. All cables and stuff are connected fine and this occurs on laptops and pcs scattered all around our offices. All cables are fine and everythign in the patch panel is fine. The network activity LEDs on the NIC and patch panel both light up. Anything I might have missed?

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Instead of using the Auto Detect option

by OH Smeg In reply to IP address woes...

For IP Addresses you need to set these manually so that this can not happen. Depending on the OS in use here the procedures vary in setting Static IP Addressing but the help files on the individual machines will tell you how it is done.

Col

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Or you could do reservations.

by bart777 In reply to Instead of using the Auto ...

Might be better than having to set static on each PC.

Give each MAC address it own reserved IP in DHCP. That way when the lease expires no other PC can grab it. This can all be done from the DHCP console on your server.

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Setup

by wesley.chin In reply to IP address woes...

What is the setup for the connection? I have seen this on occasion, often with wireless connections. Wireless is dependent a great deal on the configuration of the building, as well as placement of the router/access point, and to some degree the positioning of the antennae.

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What can happen with both WLAN clients as well as 'sleeping PCs'

by robo_dev In reply to Setup

Is that they enter the network with a duplicate IP address, and the Windows TCP/IP stack is too dumb to figure this out.

The 'best' sledgehammer solution is to do DHCP reservations for WLAN clients, as somebody else pointed out.

It sometimes helps on PCs to make sure that the Windows power settings are set not to power-off the network adapter when asleep.

It also helps to make sure the NIC drivers and BIOS are all updated.

My experience is that el-cheapo network adapters tend to have these sorts of problems with power management.

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What is providing DHCP?

by tnuke In reply to IP address woes...

Look at your DHCP server for the answers to this one. It is probably getting hung. We had a similiar problem with a Cisco PIX serving DHCP when the volume was higher than what it designed for. In our case, we had a Windows Server and enabled the DHCP on it and disabled it on the hardware device (PIX). This even happened in a shared environment because the failover of the hardware device did not want to recognize there was other DCHP servers on the network and it simply squashed the request of the PC.

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Good point...and those rogue DHCP servers can wreak havoc

by robo_dev In reply to What is providing DHCP?

One time a salesman did a demo in a conference room and plugged his netgear router into the corporate LAN.

It's DHCP server assigned 192.168.0.x addresses to about 30 workstations at Corporate HQ, including the secretrary to the company CEO!!

Believe it or not this (insert word here) salesman was selling network security software!!!

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