0

I'm trying to move the content of a Windows 2008 server to a new hardware and encountered the following problem:

The IP should be moved with the server to avoid changing lots of DNS records. Therefore I added the old server's IP as an alias-IP on the new machine. That's to avoid a longer re-configuration downtime after changing the IP mapping on the network.

But as soon as the additional IP is saved on the network adapter settings, the old server (using the same IP as main IP) can't connect to the new server (via the first/main IP) anymore.

It seems that Windows doesn't accept any incoming data connections from a machine that uses the same IP as it locally uses.

Is there any setting or workound that I'm missing or is this a by-design issue of the Windows network stack?

Edit: The new server is currently in a completely different network segment.

Emsi
  • 3
  • 5
  • I think the problem is with routing. For new server the old ip address is local (from the new server point of view). – RJS Feb 12 '13 at 02:06

2 Answers2

2

you normally can't assign an ip address two 2 machines. so don't. you will just have to cut over the ip address cold turkey when you are ready.

longneck
  • 23,082
  • 4
  • 52
  • 86
  • Of course you can assign an IP to two machines. It's required for Windows Network Loadbalancing service, just as example. However, in my scenario the new server is in a completely different IP range, so the additionally configured IP wouldn't interfere with anything on the live-system as the IP is not (yet) mapped by the network infrastructure. – Emsi Feb 12 '13 at 00:39
  • I said it's not normally possible. I wouldn't consider NLB normal. And it doesn't matter that the new server is not attached to the same network segment as the old server. Since you assigned it the IP address, it will try to connect to itself instead of the other server. The only way to stop that is to remove the IP address. – longneck Feb 12 '13 at 00:47
  • I'm not talking about connections made by the new server. Of course they would be routed locally. The problem I have is that connections from the old machine to the new one don't work. Connecting via the different IP, not the same one. That doesn't look logical to me. The new server doesn't respond to connection attempts on any IP if the connecting machine uses one of the locally configured IPs. That's actually the weird thing here. – Emsi Feb 12 '13 at 00:54
  • No, it's not. When the server sees something coming from an IP that it supposedly owns it will ignore it. Or try to respond and route the packet to itself. – longneck Feb 12 '13 at 00:59
1

The only time two servers can "share" the same IP is if you're using Clustering/Network Load Balancing. However, each server individually needs their own IP, and accept incoming connections on the Cluster IP.

It's best to assign a new IP to the new machine, and do the cut over when ready.

colealtdelete
  • 6,017
  • 2
  • 30
  • 34