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Carlos Eduardo Ribas

2012/7/19 Carlos Ribas <carlos@xxxxxxx>

Hello Stephan,

I tried to use my subnet, but didnt work. I tried to disable autoconf, no success. I also tried to manually configure the forward in Dom0 using "ip6tables -A FORWARD -s 2001:xxxx:xxxx::6 -m physdev --physdev-in vif21.0 -j ACCEPT" but once again, without success.

It's odd because if I try to ping the router from my DomU, it will not work, and this is the output from "ip -6 neigh":

# ip -6 neigh

2001:xxxx:xxxx::5 dev eth0 FAILED
fe80::224:38ff:fec9:8b00 dev eth0 lladdr 00:24:38:c9:8b:00 router STALE

From my router I can't ping my DomU, but then I got this message:

# ip -6 neigh
2001:xxxx:xxxx::5 dev eth0 lladdr 00:24:38:c9:8b:00 router REACHABLE

fe80::224:38ff:fec9:8b00 dev eth0 lladdr 00:24:38:c9:8b:00 router REACHABLE

And then it changed to:

# ip -6 neigh
2001:xxxx:xxxx::5 dev eth0 lladdr 00:24:38:c9:8b:00 router STALE
fe80::224:38ff:fec9:8b00 dev eth0 lladdr 00:24:38:c9:8b:00 router STALE

What seems to be ok, but it is not ok. Well, I'm still investigating.

Thank you for your help,
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Carlos Eduardo Ribas
2012/7/19 Stephan Seitz <s.seitz@xxxxxxxxxxx>
Hi,

as Simon already wrote, try to use your provisioned "regular" ipv6 net. This is usally
a /48 or /64.

Our dom0 don't have ipv6 configured in any way, it's just enabled by default.
Only the usual local-link (fe80...) addresses are bound to the interfaces.
If you're using bridges (peth0 -> eth0 -> vifX.X), you don't have to touch any
forwarding settings. It's "just working".

If you're using fixed addresses, don't forget to disable autoconf which is default.
E.g. :
iface eth0 inet6 static
pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/autoconf
address ...

Am Mittwoch, den 18.07.2012, 12:48 -0300 schrieb Carlos Ribas:

Hello Simon,

Yes, I'm using bridging. I put 126 as subnet mask because I configured a P-P link. Unfortunately use 64 makes no difference. However, the command you said showed me that something is wrong:

# ip -6 neigh

2001:xxxx:xxxx::5 dev eth0 FAILED

fe80::224:38ff:fec9:8b00 dev eth0 lladdr 00:24:38:c9:8b:00 router STALE

I was cheking only with this command (and looking at red line, I thought that it was all fine):

# route -A inet6

Kernel IPv6 routing table

Destination Next Hop Flag Met Ref Use If

2001:xxxx:xxxx::4/126 :: Ue 256 0 4 eth0

fe80::/64 :: U 256 0 0 eth0

::/0 2001:xxxx:xxxx::5 UG 1 0 0 eth0

::/0 fe80::224:38ff:fec9:8b00 UGDAe 1024 0 0 eth0

::/0 :: !n -1 1 73 lo

::1/128 :: Un 0 1 23 lo

2001:xxxx:xxxx::6/128 :: Un 0 1 24 lo

fe80::216:3eff:fee2:3f3d/128 :: Un 0 1 0 lo

ff00::/8 :: U 256 0 0 eth0

::/0 :: !n -1 1 73 lo

I will investigate further more. Do you think there are something wrong with "network-script" that can cause this? I hope not! :)

Thanks,

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Carlos Eduardo Ribas

2012/7/18 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.
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Re: [Xen-users] Does anybody here uses IPv6 for DomU?