Why Windows 7 takes so long to dhcp?

[nitrogen]

Hi guys, I hope this is the right forum to post this question.
I'm really curious about that and for so long I have this problem, mostly with wired connections, sometimes windows 7 takes up to 2 minutes to connect to my network and by "connect" I mean to get the connection up and running, browsing internet and accessing my network drives.

I really don't know what windows is doing during the "Identifying network" stuff. Maybe a DHCP problem? It's really annoying and after several attempts to solve this, here I am asking for some help.

My network it's really simple, I have one router TP-Link ER6120 on top of a TP-Link SG3216 switch, just the switch it's connected to the router.

Connected to the switch I have: 4 wireless routers (all in bridged mode using the ER6120 DHCP )and 4 desktops, and with no exception, everytime I wake up a computer or just turn it on, it takes almost a decade to get the connection completed with the "Identifying network" stuff, but with the laptops, phones and tablets using the wireless connection it never happens, the connection is instantly completed with no hassle.

Can you guys give an idea about what can be happening here? I really tired of moving stuff around with no success.
Thanks in advance.

 

[PrivateJoker]

The Win7 machine is hardwired in, correct?

Does it have newest, most up to date driver for its NIC? Not just the one MSFT offers, but the newest one the NIC OEM provides on the web?

Out of curiosity, turn off all the wifi bridges and reboot the machine and tell us what happens if it boots up with them off.

Is it's own network config very plain and says use DHCP for everything and the router/DNS is at 192.168.1.1, and that's it, right? Nothing fancy in there?

Is the PC configured to look for a Home Group or a Domain that doesn't actually or no longer exists?

Did you at one time map drives on that machine to shared network drives/resources that isn't there anymore? (Ie eventually shows up in the file explorer with a red X indicating it's disconnected)

What happens when you plug the PC directly into router and boot it up?

Before you do the next step, try "ipconfig /all" from the Dos prompt and look for anything that shouldn't be, or copy and paste here.

What happens if you manually assign the PC an IP address (make sure to put it outside the range your DHCP is handing out addresses).

What happens when you go to a Dos prompt and ping your router's address? What kind of results does it give? (With all your wifi bridges on, and off)

 

[coxhaus]

I think we need to explore your bridge mode of your wireless routers. What wireless routers are you running? If you plug a PC into the TP-LinkER6120 does the same problem happen with slow DHCP?

Do you have the latest firmware for the TP-Link ER6120? I think there was a fix for DHCP.

 

[nitrogen]

Guys, thanks for the quick response.
Here we go...

Q - The Win7 machine is hardwired in, correct?
A - Correct.

Q- Does it have newest, most up to date driver for its NIC? Not just the one MSFT offers, but the newest one the NIC OEM provides on the web?
A - All wired machines has the same problem, some of them with updated drivers from the manufacturer.

Q - Out of curiosity, turn off all the wifi bridges and reboot the machine and tell us what happens if it boots up with them off.
A - No Joy.

Q - Is it's own network config very plain and says use DHCP for everything and the router/DNS is at 192.168.1.1, and that's it, right? Nothing fancy in there?
A - Hahaua nothing fancy 192.168.10.0/24, Router is 192.168.10.1, Switch 192.168.10.2.

Q - Is the PC configured to look for a Home Group or a Domain that doesn't actually or no longer exists?
A - Nope, double checked.

Q - Did you at one time map drives on that machine to shared network drives/resources that isn't there anymore? (Ie eventually shows up in the file explorer with a red X indicating it's disconnected)
A - Nope

Q - What happens when you plug the PC directly into router and boot it up?
A - Woowwwww, IP Address in one second...even without rebooting, just changing the ports. Bingo, It's the switch or the Wireless stuff!!!

The switch it's new, I have changed 2 weeks ago, I replaced the SG3210 by the SG3216. Now I'm just thinking about this, since then, I'm having some problems like MacOS-X Native IPSec VPN Client not connecting anymore, Network discovery barely working to discover samba shares...about the wireless routers, nothing has changed in the last 5 months, here's my configuration:
4 TP-LINK WDR4300 routers, dhcp disabled, cable to switch connected at LAN port ( since the router doesn't have bridge mode ) and just make sure: DHCP Snooping enabled on switch with only port 1 Trusted ( ER6120 is connected at port 1 ). I have disabled DHCP Snooping just to test and problem doesn't go away.

Both ER6120 and SG3216 updated with the lastest firmware.
Coxhaus, do you see any problem with the bridge configuration described above?
I'll check the switch security stuff and I'll get back to you guys...

thanks.

 

[PrivateJoker]

Q - Is it's own network config very plain and says use DHCP for everything and the router/DNS is at 192.168.1.1, and that's it, right? Nothing fancy in there?
A - Hahaua nothing fancy 192.168.10.0/24, Router is 192.168.10.1, Switch 192.168.10.2.


Q - What happens when you plug the PC directly into router and boot it up?
A - Woowwwww, IP Address in one second...even without rebooting, just changing the ports. Bingo, It's the switch or the Wireless stuff!!!

The switch it's new, I have changed 2 weeks ago, I replaced the SG3210 by the SG3216. Now I'm just thinking about this, since then, I'm having some problems like MacOS-X Native IPSec VPN Client not connecting anymore, Network discovery barely working to discover samba shares...about the wireless routers, nothing has changed in the last 5 months, here's my configuration:
4 TP-LINK WDR4300 routers, dhcp disabled, cable to switch connected at LAN port ( since the router doesn't have bridge mode ) and just make sure: DHCP Snooping enabled on switch with only port 1 Trusted ( ER6120 is connected at port 1 ). I have disabled DHCP Snooping just to test and problem doesn't go away.

Coxhaus, do you see any problem with the bridge configuration described above?
I'll check the switch security stuff and I'll get back to you guys...

thanks.


I'll check the switch configuration, maybe something that I missed.
Thanks PrivateJoker

It wasn't until you said your switch has an IP address that I actually googled it and saw it was a managed L2 switch, so ya looks like something funky there.

My first L2 managed switch was not a fun one to learn the intricacies of while simultaneously trying to implement, administer, and sort out! Even going from one model to another relatively similar one, I'm sure isn't totally falling off a log simple, so I can empathize. Especially when you are taking it out of the box and putting it right into a critical part of the network. . .

I'm sure you'll be able to get to the bottom of it between the documentation it comes with, forums TP might have, and the guys at this website. Glad you're making progress in the troubleshooting!

 

[coxhaus]

I’m with PrivateJoker on looking at your switch since DHCP works directly connected to the router. You probably want to bring up the management screen on the old switch and compare port by port. Maybe you have a duplex mismatch. A spanning tree problem in the switch.

It is also possible you have some kind of loop going on; maybe some Ethernet teaming not setup quite right.

Of course there is always the uplink wire to the router. Maybe try a different patch cable for the uplink.

Let us know as you narrow it down.

 

[thiggins]

I see a similar problem on my network w/ wired Win 7 machines. It is a pain in the butt when I am testing and moving things around. I have never gotten around to Wiresharking the DHCP session.

What I do notice is that the DHCP session is not initiated quickly. The NIC keeps its old IP. If you disable/enable the NIC that will force a session to start. Unplugging the NIC an do it too, but it is not as reliable a method.

I don't think it is a switch problem.

 

[nitrogen]

Okay, I'm back with news, It was really the switch and the problem was exactly the security configuration, but I don't think that it's right, maybe a bug on TP-LINK SG2316?

Network Security-> Dos Defend -> Blat Attack, uncheck this guy.

After that, I have DHCP addressing instantly, no more endless "Identifying Network" stuff, Native MacOS-X IPsec VPN Client doing okay as it should and the network discovery it's working like a charm.

thiggins, Right now I'm not so sure about the problem was happening only with the wired connections. I noticed that wireless connections are faster to complete the connection after the change.

 

[coxhaus]

I see a similar problem on my network w/ wired Win 7 machines. It is a pain in the butt when I am testing and moving things around. I have never gotten around to Wiresharking the DHCP session.

What I do notice is that the DHCP session is not initiated quickly. The NIC keeps its old IP. If you disable/enable the NIC that will force a session to start. Unplugging the NIC an do it too, but it is not as reliable a method.

I don't think it is a switch problem.

I have seen DHCP have slowdowns with Win7 machines a couple times. Both times it turned out to be software problems in 2 different routers which were later fixed with newer versions of router code. All my workstations are still Win7 with older hardware.

You might try Microsoft’s DHCP server and see if it still happens. I think this would be a good test.

I have seen duplex issues but it usually causes more issues than just DHCP problems.

 

[thiggins]

Thanks for reporting back, nitrogen. Glad you got it sorted.

Coxhaus, good point that it could be my router's DHCP server. But if that is the cause it is a common problem with a lot of the routers I test. I encounter the problem when switching one of my Win 7 systems between my LAN and the router under test.

Current LAN router is a Linksys E4200. Just tried the machine over to a NETGEAR R7000 and it grabbed a new IP almost instantly. So I think you may have ID'd the problem. Thanks.