A possible solution is that your old IP Address/MAC Address for the server is cached in the mac address table on the switches. To test/fix this, log onto each of your switches and clear the mac address table with this command for Ciscos: clear arp-cache.
Something else you _might_ be able to do is remove the DNS Server from the old Windows 2000 server before shutting it down. I’ve never tried this with Active Directory installed on it, so I don’t know if it will allow you to do it.
Previously when I’ve done upgrades of this sort, I would change the DNS Servers in my DHCP scopes to point to the IP Address of the new server. I’ve never tried to replace the server using the same IP Address. I’m not certain why you want it to be the same. You could make the change to DHCP and wait for all clients to renew their IP Address and get the new DNS server before you take the Win2k server offline.
To answer your questions:
1) Taking over GC is simple, but the rest of the FSMO roles need to also be transferred. To become a GC, go into Sites and Services/Sites/Default-First-Site-Name/Servers/ServerName, right click on the NTDS Settings and Check the “Global Catalog” box. The rest of the FSMO roles can be changed using this link:
2) Hold up on this one until you get all of your roles transferred and are satisfied with your configuration. I recommend taking the Win2k server offline for awhile and making certain that you caught everything (the domain continues to function properly without it) before demoting it. You can demote it using dcpromo from the command prompt and selecting “Remote Active Directory.” Note: This is from memory, you should verify this first.
Hope this helps.