[Wiltshire] IPV6

John Larkworthy john_larkworthy at yahoo.co.uk
Tue Mar 8 15:08:14 UTC 2011


Let me talk complete rubbish. I am sure someone will correct me if I am wrong.

If  you currently run a server of any description with an IP4 address this  need 
not change. The IP6 address includes a compatability ip4 address  range so the 
DNS record can point to this. The older Win PC people will  be the ones to 
suffer as they cannot access sites like ip6.google.com because a) early MS win 
software is IP4 only b) no DNS lookup for ip6  addresses, c) ISP does not route 
IP6 addresses and finally d) the home  router does not support IP6.

I know ip6.google.com is not a loss with www.google.com accessible via IP4 but I 
quote it as an example. The real problem will  be when you need to connect with 
a website which is IP6 only (probably  in China).

How does IP6 work:

Basically it works as IP4 used to work. Each subscriber will get a 48 or 56 bit 
subnet for their own use.

Each  interface will have multiple addresses - local address, internet  address 
and respond to targeted multicast addresses. You may need more  but this is the 
minimum starting point for an internet connected host. 

The local address must be unique within the network. With IP4 this is done by a 
random number in  the subnet but with IP6 the use of the MAC 
address is recommended but either way a  broadcast or multicast request is used 
to establish that it is unique  within the LAN. 

Internet addresses are currently assigned to the WAN/LAN router in  an IP4 
network and use NAT to convert between LAN and WAN but in IP6 the  addresses 
will be directly assigned by the gateway. The gateway will  broadcast a routing 
prefix. The remainding bits must be unique within  the subnet. There are various 
policies for remaining part of the address  i.e. MAC address (or part of), user 
set, random number, etc. The MAC  address would be useful for machines expecting 
to plug and go,. User set  may be more help for servers at specific addresses. 
Finding a specific  service on the network is expected to be done using the 
service  discovery protocols like Avahi, uPnP, SLP, or Bonjour.

The simplest policy in IP6 is to use the MAC address for all  addresses and 
simply change the prefix for local and internet address.  The multicast 
addresses will then be derived from these. There are  security issues with 
allowing all hosts to have internet addresses but  there is no reason a host 
should have an internet address. The home  gateway may very well provide an 
opportunity for a fire wall.

If the idea of allowing the hosts to magic up their own addresses  does not 
apeal then DHCP v6 can be used in a manner similar to IP4.

Hope all my ramblings helps.



More information about the Wiltshire mailing list