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DHCP issues netgear

Community Veteran
Posts: 1,985
Thanks: 5
Fixes: 3
Registered: 01-08-2007

DHCP issues netgear

Posted a little about this, in the bb and routers section, with regards to my line issue, but I think its more appropriate here....
I have a Netgear DG834PN rangemax router, which has been working fine up until now.  Recently its stopped recognising my HTC wildfire S, in the attached devices settings, although the router gives it an IP, and it surfs the net with no issues.  The problems start when I start another PC on the network, and it on occasion gives out the same address, so then I get an address conflict on the network, and the new device cant access the internet.  I have tried an IPCONFIG release and renew, but it keeps getting the already in use IP.  I have got around the issue by configuring the router to give reserved IPs to specific MAC addresses, but I feel the real issue is the problem with the duplicate IPs, and the android phone not being recognised.
The router has the most up to date firmware.
Anyone any ideas.....
4 REPLIES
VileReynard
Seasoned Pro
Posts: 10,976
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Registered: 01-09-2007

Re: DHCP issues netgear

I do this as a matter of course - if I want to access another computer it's much easier to use a name, rather than an ip address.
I also duplicate this info in the hosts file of each computer.
In fact, I'd really just prefer to use static addresses...  Smiley

Community Veteran
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Registered: 14-07-2009

Re: DHCP issues netgear

I also have a Netgear DG834PN.   It went through a phase where the wired Ethernet connection to my desktop  would occasionally hang, forcing me to restart the router.  The internet connection remained up, as did wireless connections and I could still make a new wireless connection whilst the wired connection was hung.  But I have not had this issue lately.
There is always a bit of an issue with DHCP and devices going to sleep which I think is generic.  If a device is sleeping then the router may not be able to communicate with it so after a while assumes it has gone.  The router may then re-use its address if a new device is then connected.  When the sleeping device wakes up, it wakes up with its old address and there will be a conflict.  My tablet device tends to do this and after I wake it up I often have to drop and reconnect the wireless connection to get it back online.  I had always assumed this was a generic issue, although come to think of it, a DHCP assignment algorithm that worked its way sequentially through the entire address pool would be better than the one my router uses, which is to assign the lowest available address.            
MJN
Aspiring Pro
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Registered: 26-08-2010

Re: DHCP issues netgear

Penfold,
Have you tried rebooting both the router and the phone? DHCP leases are made with an expiry time so that both the server and client both know how long the address is to be reserved/used for. The lease details on the DHCP server may not persist across reboots hence it might assume a free pool and dish out an address that has already been assigned.
Rebooting the phone (or restarting the network service, perhaps even toggling wireless off/on would do it) will get the phone to request a new address. It may initially ask for a renewal of its existing lease however if the server has already reallocated it elsewhere it will refuse and provide a new address. Restarting this process may also result in it appearing in the router's 'connected clients' list.
Until the phone and router are in sync in terms of a mutually agreed address the PC will continue to get the first seemingly-available address hence the clash.
DHCP, being a stateful protocol, can sometimes get in a muddle and whilst most scenarios should be catered for by the coding on both sides issues can still occur, particularly by badly coded IP stacks such as those used in most home routers.
Mathew
Community Veteran
Posts: 1,985
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Registered: 01-08-2007

Re: DHCP issues netgear

Thanks for all the replys.
I should have realised that the phone is constantly making and breaking the wireless whenever I leave the house, sometimes for hours on end, and occasionally connecting to other wireless networks as well,  so no wonder the router is getting itself confused. As said, I have entered the phones MAC, and given it a reserved IP, as I did for the sky box and bluray player.  I did reboot the phone(something very rarely done...), and it is now showing up in the attached devices section, but coded as unknown, even though in the section to reserve an IP, I gave it a name....  Never mind at least I have some idea as to what caused the issues....