Connection status (release/renew)

cableguy1 · 22-02-2009, 16:55

Hi ppl.
I use to have a Netgear RP614V2 modem - this was a wired router and I use to change my IP quite alot - via router settings - connection status then hitting release and renew.... I have just got a new netgear router its a wireless one and on this when I hit the same options it does not change the IP, ok it gets release and renewed but the old IP shows as the current IP - I have plugged in my old router to check if it still works with changing the IP and it still does - a bit stumped on this one - any ideas ?
thanks
Edit: the new router is a WGT624 v4

KingDaveRa · 22-02-2009, 20:52

Most DHCP servers will re-allocate you the same IP, even if you do release and renew. It works on the basis that if nobody else has required the IP in the meantime, you may as well have the same one.

Begs the question, why would you want it to change? If anything, I prefer mine to be on something static, so my PC is always on the same IP. Makes tracing issues and networking faults far easier. Plus if you have NAT rules set up for port forwarding, they'll work more reliably.

cableguy1 · 22-02-2009, 21:05

Quote:

Originally Posted by KingDaveRa

Most DHCP servers will re-allocate you the same IP, even if you do release and renew. It works on the basis that if nobody else has required the IP in the meantime, you may as well have the same one.

Begs the question, why would you want it to change? If anything, I prefer mine to be on something static, so my PC is always on the same IP. Makes tracing issues and networking faults far easier. Plus if you have NAT rules set up for port forwarding, they'll work more reliably.

cheers for that. I understand what you say but I dont understand why I was able to change the IP many times when I plugged my Wired router in.... same DHCP...

mischievious · 22-02-2009, 21:21

KingDaveRa is mostly right, reallocation is not the same as static or "may as well" though.

DHCP on a lot of systems will issue an IP and make it yours for a certain period of time (varies wildly from 0-infinite time). During your lease period you will receive your existing ip, outside of this you may receive another ip. However the client "should" at lease time be given a lease duration time, in turn the client if sufficiently mature will then auto renew giving the appearance of a static ip for a while. However turn your pc off, time expires ip is available to anyone.

Obviously the DHCP server keeps record of client MAC addresses longer than your new one, this suggests that you new router is "more compliant" with modern standards by default. DHCP is not and should not be almost static, in a home environment this usually does not present a problem at home users tend to stick to 255.255.255.0 subnets which means you can have 254 devices on at all times so it matters little if DHCP is giving long/indefinte lease times. However manufacturers are now pushing the SOHO angle, that their home office equipment is also suitable for the small to medium business market hence greater compatibility with DHCP standard.

---------- Post added at 21:21 ---------- Previous post was at 21:19 ----------

Quote:

Originally Posted by cableguy1

cheers for that. I understand what you say but I dont understand why I was able to change the IP many times when I plugged my Wired router in.... same DHCP...

Sorry can't be same DHCP if you switching routers and getting DHCP from the device.

Where are you getting DHCP then?

GeoffW · 23-02-2009, 13:42

My understanding was that the renewal was typically 50% of the lease time, so for a 7 day lease, you'd renew after 3/5 days. That way your PC appears not to change it's address as you'd need to have it turned off for some time for the DHCP server to age the MAC address it associates with the DHCP lease and assign that address to another PC.

If you were seeing different IP addresses before, it could have been due to the short lease time on your old router.

KingDaveRa · 23-02-2009, 15:23

Yeah, I think it does something else clever with extending the leases, to get longer and longer between bothering to do a DHCP Renew, to save on network traffic - DHCP can get very chatty when it's ACKing and NACKing all over the place.

mischievious · 24-02-2009, 22:58

Quote:

Originally Posted by GeoffW

My understanding was that the renewal was typically 50% of the lease time

That is a client side implementation and you are right for Microsoft DHCP client. In the absence of a DHCP server it get mor and more "chatty" toward the end it starts to panic

Quote:

Originally Posted by KingDaveRa

Yeah, I think it does something else clever with extending the leases, to get longer and longer between bothering to do a DHCP Renew, to save on network traffic - DHCP can get very chatty when it's ACKing and NACKing all over the place.

No it get shorter and shorter in Microsoft land renew is a client attibute.

The renew is a client aspect. In MS land the default DHCP lease is 8 hrs so turn your PC off overnight and your lease expires. In reality it is tombstoned and it is likely you will still get the same IP anyhow.

However this is still not = "may as well be" static as this is what DHCP reservation is for. Also different devices, OS's etc may implement differently