[Wiltshire] Fwd: Re: IPV6

Guy Weatherburn guy at wiltshire-it.co.uk
Wed Mar 9 09:36:22 UTC 2011


    John has most of the pertenant points covered here. The most 
imprtant thing he says is about compatibility addresses, this had to be 
the case or it will all fall over. I will add further to the early 
windows scare (MS cockup, they did know about IPV6) and remind you that 
those running very old red hat, debian, slackware etc, servers that just 
sit in a corner and hum away will also need some attention.


-------- Original Message --------
Subject: 	Re: [Wiltshire] IPV6
Date: 	Tue, 8 Mar 2011 15:02:11 +0000 (GMT)
From: 	John Larkworthy <john_larkworthy at yahoo.co.uk>
Reply-To: 	wiltshire at mailman.lug.org.uk
To: 	Wiltslug <wiltshire at mailman.lug.org.uk>


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.


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