To back up @notverypunny when I have seen this behavior on our network, 99% of the time its rogue piece of equipment that starts handing out its own DHCP conflicting with ours. Check that users are NOT plugging in or connecting non approved devices, like travel routers or other router devices. We install a lot of equipment ofr custoemrs that our techs are suppsoed to plug into "isolated' networks and usually the , um "forget"

jt1001001
@jt1001001
Over 20 years experience in the IT field, last 13 as the Jack-Of-All-Trades I-T administrator for a NorthEast US Communications company. Familiar with all Windows O/S as well as Lync/Skype-for-Business, AdTran routers, Avaya switches, Cisco firewalls, and basic Linux tasks.
Posts made by jt1001001
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RE: Server 2019 randomly DNS stops
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RE: What Are You Doing Right Now
Fiber cut in our area causing outages. None of our offices affected directly but some of our users are down.
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RE: What Are You Doing Right Now
Server moves this evening going into colocation center will be remotely changing ip addresses and the like
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RE: Raspberry Pi 4 as IT Workstation
@JaredBusch Looks to be available today
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RE: Zyxel backdoor found
Number of their products are OEM to isp and other manufacturers. We have a DSL backup circuit using an ORM Zyxel router. Will be disconnected on Monday as we don't need it
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RE: What Are You Doing Right Now
Building new media server for home, in the research stage right now. Probably plex on a pi with a USB drive as we don't have much. Will probably build an nfs file server out of junk parts as well
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RE: Search from Start menu is blank/black
Check video drivers had this happen on 2 machines with old drivers after 20h2 came down
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RE: FreePBX vs 3CX 2021 Edition
@gjacobse you will probably be stuck with Avaya or maybe Shoretel/Mitel if the fed is involved
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RE: What Are You Doing Right Now
actually in the office for a 1/2 day today first time in I think 9 months. As always tons of junk left on my desk nothing worth keeping or saving.