OPNsense and sonic.net DHCPv6

I love the Sonic Fiber-optic Internet Service and use it in northern California. Their support is great, the price is reasonable, and the throughput is good.

One area where they were a little behind the curve is in IPv6 support. I used a 6IN4 tunnel until just a few weeks ago, after Sonic completed rollout of DHCP6 support in my neighborhood sometime last year. An issue I ran into was in receiving NoAddrsAvail in response to the DHCP6 Solicit send by my router.

14:59:58.681985 IP6 (class 0xc0, hlim 64, next-header UDP (17) payload length: 204) fe80::5e5e:abff:fed5:a1c0.547 > fe80::a236:9fff:fe59:19b0.546: [udp sum ok] dhcp6 advertise (xid=42fee3 (client-ID hwaddr/time type 1 time 656596109 a0369f5919b0) (server-ID vid 0000058335633a35) (IA_NA IAID:0 T1:0 T2:0 (status-code NoAddrsAvail)) (IA_PD IAID:0 T1:10800 T2:17280 (IA_PD-prefix 2001:5a8:xxxx:xxxx::/56 pltime:21600 vltime:21600)) (DNS-server 2001:5a8::11 2001:5a8::33))

As a result, my router did not get an IPv6 address.

igb0: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 1500
        description: WAN (wan)
        options=4800028<VLAN_MTU,JUMBO_MTU,HWSTATS,MEXTPG>
        inet 135.180.x.x netmask 0xfffffc00 broadcast 135.180.x.x
        inet6 fe80::a236:9fff:fe59:19b0%igb0 prefixlen 64 scopeid 0x1
        media: Ethernet autoselect (1000baseT <full-duplex>)
        status: active
        nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>

 

Sonic answered the question in their support forum that their DHCP6 rollout only delegates prefixes. My router needs to only send an IA_PD, not an IA_NA. With OPNsense this is done in the Interfaces setting, "Request prefix only."

 

Voila! IPv6 works from within the house.