2degrees fibre IPv6 routing settings (Linux router)

Forums › 2degrees (including Slingshot, Orcon, Flip, Stuff Fibre, MyRepublic, 2talk and Vocus) › 2degrees fibre IPv6 routing settings (Linux router)

potwercs

3 posts

Wannabe Geek

#315002 6-Jun-2024 18:15

Hi all, since it's IPv6 Day I thought I'd try to get IPv6 working on my home fibre connection with 2degrees (I've been a fibre customer since the Snap days). I did have it working previously on the old PPPoE connection, though it was never 100% reliable. My router is running Linux, so I'm on my own in terms of support from 2degrees. IPv4 connectivity is fine using the new DHCP connection option.

My understanding is that I would obtain the IPv6 netblock address via DHCP6, and the routing information via IPv6 Router Advertisements. I believe the first part of this is OK: my router has a link-local IPv6 address of:

fe80::[REDACTED]/64

and hosts on my LAN are self-assigning IPv6 addresses from my assigned 2406:[REDACTED]/56 netblock, e.g.

inet6 2406:[REDACTED]/64 scope global

I think the missing link is the default IPv6 route/gateway address, which doesn't get set even after some hours. I wondered if I could manually add the link-local address of the remote end of the fibre connection as the default route, like so:

ip -6 route add default via fe80::[REDACTED] dev eth0.10

but that doesn't work: packets go out, but there are no inbound IPv6 packets, according to tcpdump.

Notably, the remote link-local address (which I was trying to set as the gateway) is pingable:

ping6 -I eth0.10 fe80::[REDACTED]
PING fe80::[REDACTED](fe80::[REDACTED]) from fe80::[REDACTED] eth0.10: 56 data bytes
64 bytes from fe80::[REDACTED]: icmp_seq=1 ttl=255 time=11.0 ms

That's about as much as I can figure out. The interface MTUs are set to 1500, and have deactivated the firewall for testing. Any suggestions on what I might need to do to get IPv6 working? Thanks!

Edit: I should mention I'm on a static IP address, and have been since when I was with Snap.

KiwiSurfer

1464 posts

Uber Geek

ID Verified

Lifetime subscriber

#3245377 6-Jun-2024 18:43

Not sure if it's of any help as I'm not familar with the setup on Linux, but I'm pretty sure the RA doesn't assign the IPv6 address/prefix on the WAN (ONT<->Router) link. On the WAN side it is my understanding that DHCPv6 that provides the IPv6 address for the router and the prefix for the /56 delegation. Once the DHCP lease has been obtained on the WAN side, then on most routers I've used, the DHCPv6 lease on the WAN side provides a pool of IPv6 addresses for the LAN side so something on the LAN side can do automatic address assignment via IPv6 RAs using the /56 prefix to the LAN side devices.

My Microtik gets the following via DHCPv6 on our Vocus connection:-

Address 2404:4408:4600:xxxx::1

Prefix 2404:4408:4755:xxxx::/56

And all my LAN devices get addresses within 2404:4408:4755:xxxx:xxxx:xxxx:xxxx:xxxx automatically via IPv6 RAs (no DHCPv6 on the LAN side).

I'm aware you're on Linux so the process will differ but if it helps my DHCPv6 settings on Microtik are:-

DHCPv6 on the VLAN10 interface.

Request address and prefix.

Pool prefix length is /56.

There is also 'Use Peer DNS', 'Rapid Commit' and 'Add Default Route' options enabled -- not sure if these are also present in Linux.

potwercs

3 posts

Wannabe Geek

#3245712 7-Jun-2024 13:01

Thanks for the suggestions. I think the DHCP6 side of things is OK, as I'm getting an IPv6 netblock and that's being communicated to LAN hosts via the radvd daemon on my router.

I'm starting to wonder if radvd is not actually the thing responsible for receiving Router Advertisement messages from the ISP and setting the default IPv6 route accordingly. I have confirmed that my router is receiving RA/ICMP6 messages from the ISP (they seem to come through every five minutes), but nothing happens to the system routing tables. radvd does recognise the RA message, but doesn't seem to do anything useful with it, so maybe it's misconfigured.

I also discovered the rdisc6 utility, which will send a Router Solicitation, and report on the RA responses; here's what it says:

Hop limit : 64 ( 0x40)
Stateful address conf. : Yes
Stateful other conf. : Yes
Router preference : medium
Router lifetime : 4500 (0x00001194) seconds
Reachable time : unspecified (0x00000000)
Retransmit time : unspecified (0x00000000)
Source link-layer address: 84:26:2B:63:B9:71
from fe80::8626:2bff:fe63:b971

The ...:b971 address is the ISP's router. However, if I add a route for that manually, like so...

ip -6 route add default via fe80::8626:2bff:fe63:b971 dev eth0.10

...no joy (though I can ping6 the ISP's router):

ping6 2620:fe::fe
PING 2620:fe::fe(2620:fe::fe) 56 data bytes
^C
--- 2620:fe::fe ping statistics ---
6 packets transmitted, 0 received, 100% packet loss, time 5017ms

ping6 ipv6.google.com
PING ipv6.google.com(syd09s17-in-x0e.1e100.net) 56 data bytes
^C
--- ipv6.google.com ping statistics ---

7 packets transmitted, 0 received, 100% packet loss, time 6017ms

ping6 fe80::8626:2bff:fe63:b971%eth0.10
PING fe80::8626:2bff:fe63:b971%eth0.10(fe80::8626:2bff:fe63:b971) 56 data bytes
64 bytes from fe80::8626:2bff:fe63:b971: icmp_seq=1 ttl=255 time=1.23 ms

IPv6 forwarding is enabled on my router (though since my testing is on the router itself, I don't think that should matter).

I'm now not sure what would normally handle the RAs and set up the routing: I had thought it would be radvd, but maybe it's actually the kernel or some other userland service that I don't know about. My understanding is that DHCP6 is not responsible for the routing information, which is supposed to be communicated via RAs. Maybe another Linux user can clue me in...

luukp

2 posts

Wannabe Geek

#3245747 7-Jun-2024 15:00

Found this after trying to access some IPv6 addresses from home. Access works fine from my work PC but from home over 2degrees doesn't go through. I'll be looking into it further, but I'm wondering if it may be a 2degrees issue rather than a local issue. I seem to get to a 2degrees server but no further. e.g.:

Home:~$ traceroute6 google.com
traceroute to google.com (2404:6800:4006:809::200e), 30 hops max, 80 byte packets
1 default-rdns.vocus.co.nz (2404:4404:412c:c300:e246:eeff:fefd:b030) 7.386 ms 7.390 ms 7.355 ms
2 * * *
3 * * *
...
30 * * *

luukp

2 posts

Wannabe Geek

#3245786 7-Jun-2024 16:58

Actually, the first hop is the router, so it isn't even getting onto the network.

potwercs

3 posts

Wannabe Geek

#3337018 29-Jan-2025 16:20

I got it working! I had been suspicious that the external interface’s lack of a global IPv6 address was a problem, and indeed that was it. Changing the DHCPv6 client config to add Identity Association for Non-temporary Addresses (in addition to Prefix Delegation) seems to be the trick. I had tried something like this earlier but wasn’t sure where/how to do it.

For reference, I’m using IPoE rather than PPPoE. eth0.10 is the WAN interface that connects to the fibre ONT (the ".10" is for VLAN 10, which is what the ISP uses). eth1 connects to my LAN. Here’s my working dhcp6c.conf:

interface eth0.10 { 
        send ia-na 0; 
        send ia-pd 0; 
}; 
 
id-assoc na { 
}; 
 
id-assoc pd { 
        prefix-interface eth1 { 
                sla-id 5; 
                sla-len 8; 
        }; 
};

I’m using sla-id 5 for the LAN so that the IPv6 subnet matches what I’m using for IPv4 (192.168.5.*).

To start dhcp6c in debugging mode:

dhcp6c -D -f -c /etc/dhcp6c.conf eth0.10

Output from ip -6 addr:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436

inet6 ::1/128 scope host