DD-WRT v3 beta - IPv6 ISP with multiple Prefix Delegations

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Per Yngve Berg
DD-WRT Guru


Joined: 13 Aug 2013
Posts: 6180
Location: Romerike, Norway

PostPosted: Sat Jun 05, 2021 10:07    Post subject: Re: DD-WRT v3 beta - IPv6 ISP with multiple Prefix Delegatio Reply with quote
You are as far as last time. Your isp does not answer the dhcp6 request from your dd-wrt router.

fdumont wrote:
2a01:e0a:abcd:e121::/64 with Next hop to eth0 DD-WRT ipv6 address (fe80::1e88:1abc:ab12:a468).


The MAC address does not match 2a01:e0a:22a:xxx0:1e87:2cff:fe67:c469

have you tried using this address as next hop?
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fdumont
DD-WRT Novice


Joined: 23 Apr 2012
Posts: 21

PostPosted: Sat Jun 05, 2021 11:33    Post subject: Reply with quote
I updated my first post in order to be coherent with the last one (ie public IP v6 subnets 2a01:e0a:22a:xxx0 & 2a01:e0a:22a:xxx1 )

Below my DD-WRT Mac
eth0 HWaddr XX:XX:XX:XX:A4:68
vlan2 HWaddr XX:XX:XX:XX:A4:69
br0 HWaddr XX:XX:XX:XX:A4:6A

On my ISP Box I think it was necessary to indicate for nexthop the local-link IPv6 from the DD-WRT eth0 interface (so ended with 6Cool ; Am I mistaken?

vlan2 receive public DHCPv6 from ISB on the first subnet xxx0 (2a01:e0a:22a:xxx0:XXXX:XXXX:XXXX:a469/64)

So I think the ISP answer correctly to the dhcp6 request from DD-WRT router ; That's why I get a public IPv6 on vlan2 interface; That's explain that IPv6 works fine from DD-WRT router itself.

What I don't understand, it is how workstation behind DD-WRT should get IPv6 public address on subnet 2a01:e0a:22a:xxx1 : from DD-WRT router (through netmasq) or from another IPv6 mechanism ?
fdumont
DD-WRT Novice


Joined: 23 Apr 2012
Posts: 21

PostPosted: Sat Jun 05, 2021 13:06    Post subject: Reply with quote
I discover / understand (I hope) something about the difference between mode "Native IPv6 from ISP" vs "DHCPv6 with Prefix Delegation"

Mode "DHCPv6 with Prefix Delegation"
>>> Use of dhcp6c (It run command dhcp6c -c /tmp/dhcp6c.conf -T LL vlan2)

Mode "Native IPv6 from ISP"
>>> No use of dhcp6c ; I assume this mode refer to SLAAC

am I right ?

For both modes DD-WRT ipv6 works fine from DD-WRT router itself. I always get a public ipv6 address assigned to vlan2 DD-WRT interface (on the first subnet xxx0)

So I left configuration to "Native IPv6 from ISP".
Although that, I wonder how DD-WRT use the field "Assigned / Routed Prefix" (where I put subnet 2a01:e0a:22a:xxx1) --> Because I have not identified any use of this data (no ipv6 address with this subnet on DD-WRT interfaces).

So with "Native IPv6 from ISP" I add now RADVD with this config
Code:
interface br0 {
        AdvSendAdvert on;
        MinRtrAdvInterval 3;
        MaxRtrAdvInterval 10;
        prefix 2a01:e0a:22a:[b]xxx1[/b]::/64 {
                AdvOnLink on;
                AdvAutonomous on;
                AdvRouterAddr on;
        };
};


Now devices behind DD-WRT router get global IPv6 on subnet xxx1 and the IPv6 gateway is the DD-WRT br0 interface local ipv6 address (fe80::xxxx:xxxx:xxxx:a46a).

IPv6 still works fine from DD-WRT but not from Workstations
Per Yngve Berg
DD-WRT Guru


Joined: 13 Aug 2013
Posts: 6180
Location: Romerike, Norway

PostPosted: Sat Jun 05, 2021 16:52    Post subject: Reply with quote
fdumont wrote:
On my ISP Box I think it was necessary to indicate for nexthop the local-link IPv6 from the DD-WRT eth0 interface (so ended with 6Cool ; Am I mistaken?


Yes, I believe your router is a Broadcom. That means that eth0 is wifi. You must use the address from vlan2.

On the IPv6 tab, enter

Assigned / Routed Prefix: 2a01:e0a:22a:xxx1::
Router IPv6 Address: 2a01:e0a:22a:xxx1::2/64

The address is not assigned to br0. This must be a bug. You can assign it with a line in the startup script.

ip -6 addr add `nvram get ipv6_addr` dev br0
tedm
DD-WRT User


Joined: 13 Mar 2009
Posts: 451

PostPosted: Sun Jun 06, 2021 6:03    Post subject: Reply with quote
fdumont wrote:

So I think the ISP answer correctly to the dhcp6 request from DD-WRT router ; That's why I get a public IPv6 on vlan2 interface; That's explain that IPv6 works fine from DD-WRT router itself.

What I don't understand, it is how workstation behind DD-WRT should get IPv6 public address on subnet 2a01:e0a:22a:xxx1 : from DD-WRT router (through netmasq) or from another IPv6 mechanism ?


DHCPv6 is not DHCPv6-PD. Just because 1 works does not mean the other does. As Per Yngve Berg said your ISP is not responding to dhcpv6-pd requests. I could have told you this yesterday if you had supplied the make and model of the ISP box as I asked.
fdumont
DD-WRT Novice


Joined: 23 Apr 2012
Posts: 21

PostPosted: Sun Jun 06, 2021 9:49    Post subject: Reply with quote
Sorry indeed I forgot to add ISP details : Free (Freebox Optical)

tedm wrote:
DHCPv6 is not DHCPv6-PD. Just because 1 works does not mean the other does.
--> It's a quite difficult to understand for me.

DHCPv6 is working (because vlan 2 get a public IPv6 address) on the first subnet xxx0 ?

But no DHCPv6-PD : Because workstations or DD-WRT don't "catch" (know/discover) the delegation (subnet xxx1)?

tedm wrote:
As Per Yngve Berg said your ISP is not responding to dhcpv6-pd requests


DHCPv6-pd is useful/required for workstations ? not for the router itself (because it already get an ipv6 public address)

I don't understand how DHCPv6-pd works : Workstations behind DD-WRT "emit" dhcpv6-pd requests ? these requests are relayed through DD-WRT router (no filtering) to ISP box/Operator network or only to DD-WRT router ? I don't understand who should "manage" the subnet delegation (subnet xxx1) : DD-WRT router or ISP Box ?

About my DD-WRT router : Indeed it is a Broadcom (BCM4708A0). So vlan2 is the network public interface public.
fdumont
DD-WRT Novice


Joined: 23 Apr 2012
Posts: 21

PostPosted: Sun Jun 06, 2021 10:14    Post subject: Reply with quote
[quote="Per Yngve Berg"]
fdumont wrote:
On the IPv6 tab, enter
Assigned / Routed Prefix: 2a01:e0a:22a:xxx1::
Router IPv6 Address: 2a01:e0a:22a:xxx1::2/64

The address is not assigned to br0. This must be a bug. You can assign it with a line in the startup script. ip -6 addr add `nvram get ipv6_addr` dev br0


--> Really sorry, but not sure to understand. Which address is not assigned to br0 ? 2a01:e0a:22a:xxx1::2 ?

But good news indeed the command for ipv6 assignment on br0 ("ip -6 addr add `nvram get ipv6_addr` dev br0") executed manually --> assign 2a01:e0a:22a:xxx1::2 to br0 interface
Per Yngve Berg
DD-WRT Guru


Joined: 13 Aug 2013
Posts: 6180
Location: Romerike, Norway

PostPosted: Sun Jun 06, 2021 11:11    Post subject: Reply with quote
End node use DHCPv6-na to get it's client address or use radv discovery and it's MAC address to form a SLAAC address.

DHCPv6-pd is used by routers to get the prefix for it's lan scope to hand out dhcp addresses for it's clients.

With a global scope address on br0 and the correct next hop on the isp router, IPv6 routing shall now work.
fdumont
DD-WRT Novice


Joined: 23 Apr 2012
Posts: 21

PostPosted: Sun Jun 06, 2021 20:29    Post subject: Reply with quote
Great thank you ! I got "full" ipv6 working from workstation

DD-WRT GUI Web :
IPv6 IPV6 native from ISP
Assigned / Routed Prefix: 2a01:e0a:22a:xxx1::
Router IPv6 Address: 2a01:e0a:22a:xxx1::2/64

Before I was using setting DHCPv6 with Prefix Delegation & I was mistaken because I was putting local-link IPv6 from ISP box.

I simply add (as suggested by Per Yngve Berg) to startup :
Code:
ip -6 addr add `nvram get ipv6_addr` dev br0
So now br0 interface got ipv6 address (2a01:e0a:22a:xxx1::2/64)

I don't understand why or how this command attribute the correct ipv6 address but it's perfect (why xxx1::2 and not xxx1::1 ?) !

I also enabled radvd with custom config (with this workstations receive an IP address on the correct v6 subnet xxx1)
Code:
interface br0 {
        AdvSendAdvert on;
        MinRtrAdvInterval 3;
        MaxRtrAdvInterval 10;
        prefix 2a01:e0a:22a:xxx1::/64 {
                AdvOnLink on;
                AdvAutonomous on;
                AdvRouterAddr on;
        };
};


However although these good news some ipv6 web site are not available .. I don't understand how it could be possible...

Google : http://[2a00:1450:4007:808::2004]/ --> OK (& ping OK)
Microsoft : http://[2a02:26f0:e3:395::356e]/ --> Ok (& ping OK)

test-ipv6.com : http://[2001:470:1:18::115]/ip/ --> Not available (& ping KO). Ping is KO from DD-WRT itself ...

I don't understand how is it possible : ISP routing issue ? When I try using my mobile everything is fine (IP 2001:470:1:18::115 answer to ping).
fdumont
DD-WRT Novice


Joined: 23 Apr 2012
Posts: 21

PostPosted: Sun Jun 06, 2021 20:39    Post subject: Reply with quote
Really Strange

http://www.test-ipv6.com/ --> Test Failed (URL http://[2001:470:1:18::115]:80/ip/ not available)

http://ams2.test-ipv6.com/ --> Test OK (Ipv6 URL http://[2a00:dd80:3c::8aa]/ip/ available).
Per Yngve Berg
DD-WRT Guru


Joined: 13 Aug 2013
Posts: 6180
Location: Romerike, Norway

PostPosted: Mon Jun 07, 2021 3:41    Post subject: Reply with quote
I use ipv6-test.com
fdumont
DD-WRT Novice


Joined: 23 Apr 2012
Posts: 21

PostPosted: Mon Jun 07, 2021 15:52    Post subject: Reply with quote
Everything ok with ipv6-test.com.

About DHCP v6 assignment for my workstations behind DD-WRT router. Currently I set up RADVD.

What is the best (or pro/cons) between RADVD and DNSmasq ?
Per Yngve Berg
DD-WRT Guru


Joined: 13 Aug 2013
Posts: 6180
Location: Romerike, Norway

PostPosted: Mon Jun 07, 2021 16:05    Post subject: Reply with quote
DNSmasq also supports dhcp in addition to SLAAC.
tedm
DD-WRT User


Joined: 13 Mar 2009
Posts: 451

PostPosted: Mon Jun 07, 2021 17:58    Post subject: Reply with quote
fdumont wrote:

I simply add (as suggested by Per Yngve Berg) to startup :
Code:
ip -6 addr add `nvram get ipv6_addr` dev br0
So now br0 interface got ipv6 address (2a01:e0a:22a:xxx1::2/64)

I don't understand why or how this command attribute the correct ipv6 address but it's perfect (why xxx1::2 and not xxx1::1 ?) !


Because your PD request was coming from a link-local address not the actual IPv6 address.
fdumont
DD-WRT Novice


Joined: 23 Apr 2012
Posts: 21

PostPosted: Tue Jun 08, 2021 16:10    Post subject: Reply with quote
Per Yngve Berg wrote:
DNSmasq also supports dhcp in addition to SLAAC.


Could you help me with dnsmasq config ? As said currently I set up RADVD to assign IPv6 address using my subnet xxx1 (prefix 2a01:e0a:22a:xxx1::/64).

How to do the same config with dnsmasq (SLAAC) ? I don't find dnsmasq config to copy with a custom prefix.
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