default route via SLAAC not working ?

[Trond Endrestøl]

On Mon, 31 Jul 2017 15:37-0400, Mike Tancsa wrote:

> On 7/31/2017 2:13 PM, Trond Endrestøl wrote:
> > 
> > That's strange. I've never seen such behaviour before.
> > Maybe a packet capture can provide more clues.
> 
> Not sure whats going on from the pcap. I dont see any values in there
> that would tell the kernel to expire a setting in less than 5min

I compared your router's advertisement with the core switch at work:

>From your network:

10:05:51.261641 a4:71:74:2b:c1:37 > 33:33:00:00:00:01, ethertype IPv6 (0x86dd), length 118: (hlim 255, next-header ICMPv6 (58) payload length: 64) fe80::a671:74ff:fe2b:c137 > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 64
        hop limit 64, Flags [managed, other stateful], pref high, router lifetime 1800s, reachable time 0s, retrans time 0s
          prefix info option (3), length 32 (4): 
2605:8d80:6e3:7365::/64, Flags [onlink, auto], valid time 7200s, pref. time 3600s
            0x0000:  40c0 0000 1c20 0000 0e10 0000 0000 2605
            0x0010:  8d80 06e3 7365 0000 0000 0000 0000
          mtu option (5), length 8 (1):  1460
            0x0000:  0000 0000 05b4
          source link-address option (1), length 8 (1): a4:71:74:2b:c1:37
            0x0000:  a471 742b c137

>From my work network (slightly anonymized):

13:48:16.506259 IP6 (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 64) fe80::1 > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 64
        hop limit 64, Flags [other stateful], pref high, router lifetime 1800s, reachable time 0s, retrans time 0s
          source link-address option (1), length 8 (1): 00:12:34:56:78:9a
            0x0000:  0012 3456 789a
          mtu option (5), length 8 (1):  1500
            0x0000:  0000 0000 05dc
          prefix info option (3), length 32 (4): 2001:db8:1234:5::/64, Flags [onlink, auto], valid time 2592000s, pref. time 604800s
            0x0000:  40c0 0027 8d00 0009 3a80 0000 0000 2001
            0x0010:  0db8 1234 0005 0000 0000 0000 0000

Your router has the "managed" flag and the "other" flag turned on. 
Does the router provide DHCPv6 service? If it does, then you need a 
DHCPv6 client, e.g. net/dhcp6 or net/dhcpcd.

If you can turn off the "managed" flag in the router's advertisements, 
then SLAAC should work out of the box. You would still need a DHCPv6 
client to extract the DNS information, unless you want to handle that 
through DHCP for IPv4 or do it manually.

-- 
Trond.