i’m trying to request a /56 prefix by setting prefix length to /56 under PD config but im only getting /64. The docsis modem/router model is Xfinity XB8 and the router’s internal menu shows the isp router itself is getting a /56 from the ISP.
I assume if the isp router can request /56 from the isp, then vyos should be able to as well??
I sat down and tried REALLY HARD to summon into my brain the config you’re using, but it just wouldn’t work.
Any chance you can share it instead? 
I would agree with your assumption though.
Just because the router receives a /56 from upstream doesnt mean it will share that whole range as a single /56 downstream. It will most likely be smaller than that such as in block of /64 or so.
I think that’s correct. Individual LAN subnets will be /64 (derived from the /56 delegated prefix).
Here’s a snip of my config that successfully pulls a /56 prefix from Charter for the WAN (eth0) and gives a /64 to the LAN (eth1). Should work with Comcast Xfinity, too.
set interfaces ethernet eth0 address ‘dhcpv6’
set interfaces ethernet eth0 description ‘WAN’
set interfaces ethernet eth0 dhcpv6-options no-release
set interfaces ethernet eth0 dhcpv6-options pd 0 interface eth1 address ‘1’
set interfaces ethernet eth0 dhcpv6-options pd 0 interface eth1 sla-id ‘1’
set interfaces ethernet eth0 dhcpv6-options pd 0 length ‘56’
set interfaces ethernet eth0 dhcpv6-options rapid-commit
set interfaces ethernet eth0 ipv6 address autoconf
set interfaces ethernet eth1 description ‘LAN’
set interfaces ethernet eth1 ipv6 address autoconf
sorry this is the config:
the isp modem/router is in bridge mode, vyos receives a different prefix than the isp router but only /64
set interfaces ethernet eth0 disable
set interfaces ethernet eth1 address ‘dhcp’
set interfaces ethernet eth1 address ‘dhcpv6’
set interfaces ethernet eth1 description ‘WAN’
set interfaces ethernet eth1 dhcpv6-options pd 0 interface eth2
set interfaces ethernet eth1 dhcpv6-options pd 0 length ‘56’
set interfaces ethernet eth1 ipv6 address autoconf
set interfaces ethernet eth2 address ‘192.168.1.1/24’
set interfaces ethernet eth2 description ‘LAN’
set interfaces ethernet eth2 ipv6 address autoconf (as suggested by Gus but didn’t work)
set interfaces ethernet eth3 disable
Yea totally agree - I read his message as he was seeing only a /56 from his ISP using VyOS but I think you’re right.
Check the following command to see what actual prefix you’re getting from your ISP:
show log | grep "IA_PD prefix:"
Shows me getting a /56 from my ISP
Jul 27 19:29:00 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 19:34:07 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 19:39:14 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 19:44:21 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 19:49:28 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 19:54:35 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 19:59:42 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 20:04:50 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 20:09:57 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 20:15:04 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
Jul 27 20:20:11 dhcp6c[19929]: copyin_option: IA_PD prefix: 2406:xxxx:xxxx:c900::/56 pltime=615 vltime=615
set interfaces ethernet eth0 vif 10 dhcpv6-options pd 0 interface eth1 address '1'
set interfaces ethernet eth0 vif 10 dhcpv6-options pd 0 interface eth1 sla-id '1'
set interfaces ethernet eth0 vif 10 dhcpv6-options pd 0 length '56'
As @gus mentions this only gives me a /64 downstream on my LAN side.
show log | grep "IA_PD prefix:"
Aug 04 23:11:45 dhcp6c[2024]: copyin_option: IA_PD prefix: xxxx:xxxx:60d7:da00::/56 pltime=3600 vltime=3600
Aug 04 23:11:46 dhcp6c[2024]: copyin_option: IA_PD prefix: xxxx:xxxx:60d7:da00::/56 pltime=3600 vltime=3600
Aug 04 23:11:54 dhcp6c[2767]: copyin_option: IA_PD prefix: xxxx:xxxx:60d7:da00::/56 pltime=3600 vltime=3600
Aug 04 23:11:55 dhcp6c[2767]: copyin_option: IA_PD prefix: xxxx:xxxx:60d7:da00::/56 pltime=3600 vltime=3600
Aug 04 23:20:14 dhcp6c[4186]: copyin_option: IA_PD prefix: xxxx:xxxx:60d7:da00::/56 pltime=3600 vltime=3600
Aug 04 23:20:15 dhcp6c[4186]: copyin_option: IA_PD prefix: xxxx:xxxx:60d7:da00::/56 pltime=3600 vltime=3600
log shows i am getting a /56 but /64 on the LAN side, same as Gus, interesting. I guess this is resolved. thanks guys.
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