Tech Blog

Today was an interesting, over the bank holiday I demoted an old 2003 domain controller, let’s call it Server1.

All went to plan, changed the IP address of the DNS on the network card and ran DCPROMO, nexting through all the options.

Reboot, ran a few tests:

DCDIAG on all the remaining domain controllers,
REPADMIN /REPLSUMMARY to test replication,
Logged onto a few PC’s to check they could authenticate ok.

Well that all seemed fine and all the results were great.

Tuesday comes round and I turn up to bedlam!!

Around 20 or 30 machines were referencing Server1 for DNS and since the dcpromo the DNS server only had Active Directory integrated DNS running meaning users couldn’t get to a host of sites!!

The question was though, why on earth were they referencing Server1?

To try and resolve I did the normal client side:

 Rebooted the client,
IPCONFIG /Release,
IPCONFIG /Renew,
IPCONFIG /FlushDNS,
Changed the settings in the registry:  HKLM/CCS/Services/TCP/Parameters

But no matter what I did the DNS server reverted back.

So after some thought I logged onto Sercver1 and checked DHCP because as you know DHCP assigns DNS and the default gateway etc to clients.

The service was enabled which worried me slightly and the Scopes were disabled but more importantly the Server options were all referencing the wrong server!!  So I quickly changed the options then disabled the DHCP service.

Rebooted the clients and Bam, everything was back up and running as it should.

For some strange reason the clients were using the  wrong DHCP server along with its incorrect settings.

So I urge you if you have this problem check all your DHCP server first!!

Occasionally you may want to force traffic through a specific network interface.

For example, you have a VPN and you don’t want Chrome or IE (really, you use IE?)  to use the VPN as its slow and certain web sites may be restricted (because you shouldn’t be looking at facebook all day!)!

So what you need to do is change the network interface for the VPN to have a HIGH metric in the Advanced properties of the Networking interface.

This will force all traffic through your other network connection BUT and this is a big BUT, do the below after you have connected to what ever it is you want to connect to via your VPN (does that make sense? if not let me know in the comments)!

Turn your machine on, connect to the internet and then connect to the VPN, connect to what ever it is you do on your VPN,

Then Go to Network connections

Properties of undesirable network interface (VPN in this case but could be a Ethernet connection if you want to use your wireless for internet rather than Ethernet)

Properties > Double Click Internet Protocol Version 4 > Advanced

Deselect Automatic Metric

and enter a high number like 500

Ok Out,

and open Chrome or IE or what ever and check the IP to see what interface your routing out off!

Done

Had an annoying error today while trying to add a ESX 4.1 host to DataCenter:

Call “datacenter.queryconnectioninfo” for object “DC or Cluster Name” on vCenter Server “vCenter” failed.

Firstly I thought my password may be wrong for the host, it wasn’t!

Then, maybe my new host is in maintenance mode, it wasn’t!

Finally, and really it should of been obvious to me:

I’d changed the IP address twice while building the box via the console and had forgotten to enter a new default gateway!

And Bam, added the host to the Datacenter!!