DHCP & DNS Issues

glenimp617 · 11 Sep 2020 at 09:02

Need to pick some technical brains please:

I have my IT dept arguing with each other at the minute, so I'd like a second opinion.

The first line guys say that when laptops are moving between buildings in our company, the IP address is changing (buildings are on different subnets), but when they try and remote control using the machines name, it's trying to connect to the old IP address.

Looking in DNS, it's got the old IP of where the machine was a day ago.

The third line team are saying this is normal behaviour, but the first line team are getting annoying at not being able to use machine names, and having to spend a few extra mins each time in tracking down the new IP.

I know DNS scavenging, it's switched on.

any ideas?

paradigm · 11 Sep 2020 at 10:55

Are the machines set/allowed to update their DNS records? Also do you have reverse DNS zones?

I know at a previous employer they ditched MS DNS in favor of running Infoblox, but disabled any dynamic and/or non administrative updates which lead to the same situation you are now in (DNS records being stale and computers having different IPs from their DNS records).

Terrier_Jimlad · 12 Sep 2020 at 01:19

Scavenging might be on, but what is it set to?

In environments where scavenging isnt much help, popping a quick ipconfig /registerdns at machine startup might be a decent work-around

glenimp617 · 12 Sep 2020 at 17:24

Thanks I'll check both

teaboy5 · 13 Sep 2020 at 16:09

TheOracle said:
Need to pick some technical brains please:

I have my IT dept arguing with each other at the minute, so I'd like a second opinion.

The first line guys say that when laptops are moving between buildings in our company, the IP address is changing (buildings are on different subnets), but when they try and remote control using the machines name, it's trying to connect to the old IP address.

Looking in DNS, it's got the old IP of where the machine was a day ago.

The third line team are saying this is normal behaviour, but the first line team are getting annoying at not being able to use machine names, and having to spend a few extra mins each time in tracking down the new IP.

I know DNS scavenging, it's switched on.

any ideas?

In a normal MS envir this is normal. We have the same issues with people travelling to different buildings and the subnet changing, so this causes issues with the fortigates allowing internet. Normally after 5 minutes of being on the new subnet it sorts it self out.

Scavenging is set as low as it can go.

glenimp617 · 13 Sep 2020 at 16:43

teaboy5 said:
In a normal MS envir this is normal. We have the same issues with people travelling to different buildings and the subnet changing, so this causes issues with the fortigates allowing internet. Normally after 5 minutes of being on the new subnet it sorts it self out.

Scavenging is set as low as it can go.

Yeah we also have a fortinet firewall

I'm sure the guys were saying it was an issue for days

teaboy5 · 13 Sep 2020 at 20:51

TheOracle said:
Yeah we also have a fortinet firewall

I'm sure the guys were saying it was an issue for days

So it just the internet that doesn't work? That's all our issue is as network is fine. Its normally down to the F/G SSO client on the DC's. It still think the laptop has the same DNS, but does update it within about 5 minutes, but of course when people tell us that 5 minutes is either 10 to 30 minutes.

sideways14a · 13 Sep 2020 at 20:55

Seen this before, one of the things we have to help is a dynamic screen backdrop app that adds to the desktop the pc name, domain and IP address. Its dead handy when on the horn to someone who doesnt know there return key from there toilet flusher.

Of course there are times the little so and so doesnt update and the end user reads out the old IP.....