Using TCP/IP Version 6 (IPv6) can make network slow

Internet Procotol ver. 6 (IPv6) contains many new improvements:

  • 128 bit address space (IPv4 uses 32 bit)
  • Easier configuration (IPv4 uses DHCP or manual setting static IP address)
  • Built-in security
  • Better support for Quality of Service (QoS)

Sadly enough not all Internet Service Providers (ISP) are able to handle IPv6 properly. For example some IPv4 DNS servers cannot handle IPv6 “AAAA”-record lookup requests. Instead of replying NOERROR and an empty reply, then they respond NXDOMAIN or NAME_ERROR or not responding at all. This either causes very slow DNS lookups because of timeouts or failure to perform the DNS lookup at all.

To uninstall IPv6 (And only use IPv4) in WinXP:
  1. Open Control Panel -> Network Connection
  2. Right Click the network interface card, and select Properties.
  3. Select IPv6 and press Uninstall
    • Vista/Win7 cannot uninstall IPv6 but clearing the checkbox for IPv6 will disable it for the network connection. More Info MS KB929852
  4. Restart

More Info MS KB325449
More Info MS KB815768
More Info MS KB817778