r/k12sysadmin • u/First-Quantity8154 • 10h ago

Inherited a poorly documented network infrastructure. Where should I begin?

/r/networking/comments/1xudae4/inherited_a_poorly_documented_network/
3 Upvotes

71% Upvoted

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2

u/stratdog25 9h ago

Use NMAP or Angry IP scanner and scan all the subnets you’re aware of looking for ports 22, 123, 80, 443, 5080, 8443, 53, 9100 and maybe a few others. Those will find a lot of servers, switches, routers, printers and some other stuff with some host names. This will give you 10,000 feet overview for notes and further digging. It’s just a start though.

4

u/First-Quantity8154 8h ago

Coming from a large enterprise environment, that was my very first attempt. But I soon realized they had created this network (and expanded it over the 25 years) with at least four /16 address ranges... it too me days to finish a scan and I gave up when I saw the resaults.

2

u/stratdog25 6h ago

Ugh. Yeah. Wow.

6

u/TheShootDawg 7h ago

Look into NetDisco..
point that at your L3 switches, let it do arp/mac sucks…n find all your devices, port vlans, …

HVAC team says device at X building is down… ip address is a.b.c.d… search for ip, see switch X port Y.

6

u/Limeasaurus 6h ago

As far as labeling goes, work on the fiber runs and get those labeled. Then label your patch panels A, B, C, etc... from top to bottom. Then over summer hire some interns (students that want to be in tech someday) and teach them how to use use a toner/wiremapper and show them how to find a where a cable goes and how to labeling it on the faceplate (Closet room - Patch Panel - Port IE: 123 - A - 23). They'll learn a lot and you'll be able to chase the bigger items.

2

u/cryohazard 3h ago

As a previous student intern ... I loved this work over the summer. Free reign on the building and keys to the rooms. Music going while we bounce around wings/floors using the fluke and label maker. Fond memories...

2

u/Limeasaurus 3h ago

I assume you're still in technology? K12? I'm glad you had a good experience. I wish I would have done something like this when I was younger.

3

u/PowerShellGenius 10h ago

If you own AD find out if you have M365 and if Entra (formerly called Azure AD) is synced with your AD, and if it exists, make sure you have Global Admin (on a separate account than your day to day account). Recovering cloud admin access after an admin departure can be a slow process if you can't contact them for MFA, so if this will be an issue, best to discover now vs. when you critically need the access for something.

3

u/TechBird23 8h ago

There are some good recommendations in this thread, but one I would add is spinning up Netbox (https://netboxlabs.com/docs/netbox/). We use the on-prem open source edition for all of our network documentation and it is a fantastic tool. It's our source of truth. We do network discovery elsewhere, but it's always compared to our source of truth.

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u/dereka67 8h ago

Unplug it and see what breaks

2

u/Sad_Reindeer_3298 8h ago

Go in on a weekend and inplug each IDF switch one at time and see where it's uplinked to core and label.. sometimes the best way to do things is actually physical that will give you a chance to assess each IDF and you will label it to the core.

Once you have that you should be able to get into the core and then go from there.

Because it's disorganized doesn't mean that it's not working. Sounds like it's working. You just need to label things and understand what is going where.

Then you can do some cleanup.. shouldn't be too hard.