fib 1 DHCP and RA default route

I'm setting up a new router that has both an ADSL/PPPoE and a cable modem upstream. I've configured mpd5 for the PPPoE connection, and I'd like to have the cable modem provide a second, independent connection through FIB 1 over igb2.

rc.conf (partially):
ifconfig_igb2_descr="Cable Modem"
ifconfig_igb2="DHCP fib 1"
ifconfig_igb2_ipv6="inet6 accept_rtadv defaultif"

gateway_enable="YES"
ipv6_gateway_enable="YES"
pf_enable="YES"

dhclient_flags="-b"
dhcp6c_enable="YES"
dhcp6c_interfaces="igb2"
dhcp6c_fib=1

I think this should be sufficient to receive both an IPv4 and IPv6 address and a default route, however, neither one is added. When I manually add them, they are removed after a while.

$ ifconfig igb2
igb2: flags=8863<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
	description: Cable Modem
	options=4e527bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,WOL_MAGIC,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6,NOMAP>
	ether 00:0d:b9:xx:xx:62
	inet6 fe80::20d:b9ff:fe58:5262%igb2 prefixlen 64 scopeid 0x3
	inet6 2a02:8108:0:90:xxxx:8eb4:28c2:6315 prefixlen 128
	inet 31.16.xxx.4 netmask 0xffffff00 broadcast 31.16.xxx.255
	fib: 1
	media: Ethernet autoselect (1000baseT <full-duplex>)
	status: active
	nd6 options=8023<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL,DEFAULTIF>

$ setfib 1 netstat -rnfinet
Routing tables (fib: 1)

Internet:
Destination        Gateway            Flags     Netif Expire
31.16.xxx.0/24     link#3             U          igb2
31.16.xxx.4        link#3             UHS         lo0
127.0.0.1          link#4             UHS         lo0

$ setfib 1 netstat -rnfinet6
Routing tables (fib: 1)

Internet6:
Destination                       Gateway                       Flags     Netif Expire
::/96                             ::1                           UGRS        lo0
::1                               link#4                        UHS         lo0
::ffff:0.0.0.0/96                 ::1                           UGRS        lo0
2a02:8108:0:90:xxxx:8eb4:28c2:6315 link#3                       UHS         lo0
2a02:8108:xxxx:9d00::/64          link#17                       U         br103
2a02:8108:xxxx:9d00:0:ff:fe00:367 link#17                       UHS         lo0
fe80::/10                         ::1                           UGRS        lo0
fe80::%igb2/64                    link#3                        U          igb2
fe80::20d:b9ff:fe58:5262%igb2     link#3                        UHS         lo0
ff02::/16                         ::1                           UGRS        lo0


For IPv6, I thought that setting defaultif would make the kernel add the default route when an appropriate RA is received, and on my old router, that was working; I can't seem to see what difference I have in the config, apart from using FIB 1 instead of the default.

And for IPv4, I see that I get the default router through DHCP, but somehow /sbin/dhclient-script is not adding a default route. If I add it manually, it will be removed eventually.

Any suggestions?


Stefan

--
Stefan Bethke <stb@lassitu.de>   Fon +49 151 14070811