this post was submitted on 29 Dec 2023
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Weird problem driving me crazy (Win, Domain, Network) (lemmy.zip)
submitted 1 year ago* (last edited 1 year ago) by [email protected] to c/sysadmin
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[Update:Solution]

It was my router which set STP on by default. Switching it off (in smaller networks) or using RSTP made the delays go away.

[/Update]

Hóla!

For a long time I've got this horribly annoying problem: Upon bootup, ANY domain-machine that is using LAN (no probs with wireless) has an idle-time with "there's no network!" of about 1-2mins until they discovered the network. BUT only windows-machines. Linux boxes get net instantly. Also on LAN.

Setup: 2 Domaincontrollers, Server2019. Both are DNS, one is DHCP and NPS for WIFI. All machines have fixed IPs, the DHCP is just for wireless clients.

I have tried everything I could think of, like NIC-Drivers, OpenDHCP, temporarily changed the switch from a managed one to a dumb one, changed the NIC in the server, let only one DC be alive at a time, rejoined the domain, the usual sfc/dism-approach and whatnot.

I asked once on reddit, but everyone just told me "that's DHCP!", yet it's (seemingly at least) not. All have fixed IPs, but using dhcp doesn't change a thing.

So I'm clueless again, hoping for some nerd that's nerdier than me to have an idea :)

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[–] IHawkMike 7 points 1 year ago (3 children)

Check the following during this unknown network window:

  • What does ipconfig /all show
  • Can you ping the gateway?
  • What does arp -a show?
  • Is there anything in the NCSI log?

Also are your wireless clients on a different VLAN than your wired clients? Does the firewall treat this traffic differently in any way? Does DHCP give out different DNS settings than wired?

[–] [email protected] 4 points 1 year ago

NVM, I finally found the culprit by accident....my switch enabled STP (slow) by default. Switching it off or using RSTP fixed the delays. Thanks for helping anyway man!

[–] [email protected] 2 points 1 year ago

Will do the bootup-script! Good idea.

The wireless were on a different VLAN. Also changed that for troubleshooting. Now everything is the same and got the same firewall-rules. Which i also completely disabled. And no, DHCP is the same for all too.