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DHCP boottime


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trying to find some anwsers to some questions that have been brought up at work lately,

finding on several laptops that from boot-up, it takes the DHCP server almost 20 seconds to lease out an IP address to a given machine, from that poin the machine is not pingable unitl 80 seconds into the boot and finally is able to find the domain. has anyone else done a network trace of a XP boot on their domain lately, would anyone want to :). just seems to me that from boot till 80 seconds to finally begin authentication with the domain and actually respond to network resources is a long time

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I just looked at ours. The times were very similar. took 21 seconds before it recieved a DHCP address and then took 75 seconds before it was pingable. Cant tell you if its always been this way since I just started but it does seem a bit slow to me this way. I know this is an old post but I am hoping you found out the problem as This is a 2000 server and not 2003 (Cheap people!) Anyway let me know

have a good day.

Edited by ruralpctech
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Using fixed or reserved IP:s may speed it up quite a bit, but that may not be an option in this case?

:) sadly that isn't an option, with over 9000 desktops in several buildings (nevermind the international sites) that would be a nightmare.


thanks for the stats, we are running a full W2k3 domain in 2003 native mode, DHCP and DNS are hosted on the same machine (shudder i have told them to switch them but they are cheap sometimes) this is fairly standard across all buildings with 5 laptops of the same make and install, scares me to think that it should be like that, building a couple new machines and i will test it again tommorow.

anyone else willing to check their times?

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I wonder if it has something to do with DNS?? Timing out maybe??

I mean it has a list of things to go down first

Local Cache






if it times out on all usually Broadcast will pick something up. Just an idea.

Going to check it when I get back

Edited by ruralpctech
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DNS shouldn't play apart till i get an actual IP address, all the DNS related information is populated by the DHCP server. talked with some other IT folk and it seems to be the case on their networks as well, semi disturbing that it would take that long to aquire an IP address

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It would be interesting to see a network trace from the client port as well as the DHCP server port during this time - does the time delay seem to occur on the client, or does the initial discover packet get to the DHCP server and then it takes ~20 seconds to send out the offer? Where in the DORA process is it slow, and on which end?

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i don't have the DHCP server side port checked but from the client side,

DHCP request goes out at 21 seconds into the boot

DHCP Inform at 34 seconds

DHCP infrom at 37 seconds

another DHCP request goes out at 39.11 seconds

Ack Comes back at 39.12

i'll find out if i can get the port for the DHCP server monitored.

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We have this problem at work sometimes...because we always have to guess how the port is setup on the switch. :realmad:

Most of our ports are forced to 100/Full. If the NIC is configured for Auto, then a duplex mismatch will occur and the NIC will negotiate at 100/Half. This is by design. I've been arguing this with the guys who manage our switches because:

1. I hate having to figure out which way the port is configured

2. I hate having to manually configure the NIC if the port is 100/Full

3. No way to script the speed/duplex settings on most NICs*

4. Some printers don't allow you to configure the speed/duplex (Dell 5210's and 5310's don't)

I actually had one of the guys tell me that 100/Half was better than 100/Full!! He said "oh yeah, we configure other people for 100/Half and they say that it's soooo much better". To which my response was "yeah, because now the NIC and switch aren't fighting over the duplex mode". But what do I know? :)

Anyway...my point was that it's one more thing for you to check. Once our machines are configured correctly for the switch port, they're generally pingable shortly after the Windows GUI appears during the boot process.

*Intel is one of the few NIC manufacturers to provide a utility, but it doesn't work on all of their NICs

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The only other wrench in the works is the use of security on the switches, like 802.1x or other certificate/radius implementations, which can slow the process down immensely. Although, if this was the case, you'd see it on desktops too, likely.

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