Re: IPv6 routing, Verizon FiOS, dhcpcd

> On Oct 6, 2025, at 00:34, Tom Pusateri <pusateri@keehole.org> wrote:
> 
> Getting a router advertisement is independent of getting an IA_NA global address for your upstream interface, however, the provider could be filtering your router until it gets a DHCPv6 round trip.

Understood.  Also note that my provider won’t give me an IA_NA, it
is giving me an IA_PD.  I tried to get an IA_NA from them when I started
playing with this a year ago, they never give one.

> Use tcpdump to capture the router advertisements on your upstream interface. This will show router advertisements and router solicitations. In my case, they’re sent about every 24 minutes. A router solicitation would trigger one at restart.

I have the RS’s and RA’s.  What I am _not_ seeing in tcpdump is 
neighbor advertisements in response to my NS’s.  At least, when
the problem is occurring.  I can wait for hours, and I never get
an NA for the router I’m NS’ing for.

I see now that in my test where I delayed dhcpcd startup, I do get
NS back, so that makes sense.  But I can’t imagine how when I start
dhcpcd affects whether or not Verizon responds to my NS.

> See if you have a default route and try pinging the default IPv6 route:

Yup, I did all of this in my initial testing before I fell back to
trying with a spare machine.  There is no default route, but even
with a config such that dhcpcd sets a default route (it will if I’ve
told it to assign an internal address from the IA_PD allocation, not
otherwise) then the next-hop LL is always “(incomplete)” in ndp -an
output.

> Does this act the same with another DHCPv6 client like KAME dhcp6c instead of using dhcpcd?

I have not tested others.  Again, I don’t think it’s a DHCP thing,
The DHCP part is actually working.  It’s that something else is
Happening at an addressing level.

Your comments about the ONT doing something make me wonder if it
could be that, but I’m not sure why that would be different depending
on delaying starting dhcpcd, or what I can do to avoid it.  Though
I guess if I could confirm that, then at least I would know it’s
a problem unique to me.

Thanks.

     - Chris