Re: [Xen-users] Does anybody here uses IPv6 for DomU?

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

Carlos Ribas wrote:

> I am trying to do some tests with IPv6. I would like to configure a 
> dual stack for some services, such as DNS and Web Server.
> First of all, to have IPv6 in DomU should I configure IPv6 in Dom0? 
> I'm not sure, but I dont think so, since from Dom0 using loopback 
> address I can ping the IPv6 address from my router.
You don't need any address of Dom0 (I'm assuming you are using bridging ?)

I have one DomU running IPv6 for testing (DNS, Web server), Dom0 and 
the rest of the network is IPv4 only - well as much as you can when 
everything defaults to at least configuring link-local IPv6 addresses.
> # The primary network interface
> auto eth0
> iface eth0 inet static
>  address 10.0.0.100
>  gateway 10.0.0.1
>  netmask 255.255.255.0
>  broadcast 10.0.0.255
>
> iface eth0 inet6 static
>  address 2001:xxxx:xxxx::6
>  netmask 126
>  gateway 2001:xxxx:xxxx::5
That looks OK, I'm running a Hurricane Electric tunnel so mine looks different.

> But I cant ping the IPv6 address from my gateway. My routes seems to 
> be OK. Should I configure something else? I was looking in google 
> and saw some people saying about to check /etc/sysctl.conf, 
> specially the line "net.ipv6.conf.all.forwarding=1", but this dont 
> did any difference.
I have "post-up echo 1 > /proc/sys/net/ipv6/conf/all/forwarding" in 
the IPv6 stanza in my /etc/network/interfaces. But that is only 
needed to make the machine route packets between networks (ie act as 
a router for other devices' traffic), it will still talk to other 
devices without this.
> (network-script 'network-bridge antispoof=yes')
> (vif-script vif-bridge)
Standard advice now is not to use a network-script. It made sense a 
while back, but the scripts are deprecated and the host OS generally 
has better tools. For example, in Debian you can put something like 
this in /etc/network/interfaces :
auto br0
iface br0 inet static
        bridge_ports eth0
        address a.b.c.d
        netmask 255.255.255.0

One things I suggest it might be worth looking at is your subnet 
mask. Try using 64 instead of 126 and see if it makes any difference. 
While technically a 126 bit netmask ought to work on a P-P link, in 
practice I believe there are a lot of things that break if you go 
less than 64 bits for the host part of the address.
Also, "ip -6 neigh" will show you the known IPv6 neighbours (roughly 
equivalent to ARP cache for Ipv4). That may help in debugging.
--
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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