[Networking] Opnsense ipv6 prefix changing at every reboot - Verizon FiOS (2024)

dmb
join:2002-12-03
Morristown, NJ

dmb

Member

2024-Apr-10 7:13 pm

[Networking] Opnsense ipv6 prefix changing at every reboot

Hello, I am trying to determine if I have opnsense configured wrong, or if this is the reality of fios and ipv6. It seems my prefix changes every time dhcpv6 asks for a ipv6 prefix from fios upstream. My ipv4 address will be the same (and seems to loosely be based on my mac address), but ipv6 prefix changes every time. This makes things a little ugly around my house if I am rebooting a router, and not every device in the house, as ipv6 sent via radvd and dhcpv6 to my devices tend to be sticky for a while, before they try to grab new ones, breaking ipv6 routing until I ask them to renew (or simply reboot them). Anyone seeing same behavior, how about on the provided fios router?

· actions · 2024-Apr-10 7:13 pm ·

philly_ipv6
join:2022-09-07
Harleysville, PA

philly_ipv6

Member

2024-Apr-10 9:11 pm

there are some extra items that you can try to add to your DHCPv6 configuration if opensense has the options to support them.
I had success with a fortigate keeping the same prefix between reboots.
prefix-hint-plt: 0 prefix-hint-vlt: 0
preferred-lifetime: The recommended preferred lifetime for the IPv6
prefix in the option, expressed in units of
seconds.

valid-lifetime: The valid lifetime for the IPv6 prefix in the
option, expressed in units of seconds.

A value of 0xFFFFFFFF equivalent to the decimal value of "-1". represents infinity.

Being on the client side its not clear if these options are honored by the Verizon DHCPv6 server. But worth a shot.

· actions · 2024-Apr-10 9:11 pm ·

dmb
join:2002-12-03
Morristown, NJ

dmb

Member

2024-Apr-13 8:29 am

Will have to try that soon, opnsense doesn't support in the UI, but they allow to specify a dhcpv6 configuration file which replaes UI config. Need to construct it with existing stuff, along with those 2 params to see if it makes a diff (when the house can afford downtime while I play:))

· actions · 2024-Apr-13 8:29 am ·

wteiken
join:2015-12-29
Cortlandt,NY

wteiken

Member

2024-Apr-28 5:03 pm

You can also configure radvd to invalidate the prefix when it terminates via DeprecatePrefix. That should help during reboots as the clients should consider the prefix expired once radvd stops. Not perfect as the announcements can be missed, but works for me so all clients recover within a minute or two when I test a prefix change.

But not sure why you get a new prefix in the first place. Is it configured to release the prefix on reboot? For me the prefix stays stable for a long time across reboots as long as it does not get released when the dhcp client stops. I had the same almost a year until a longer outage caused the lease to expire.

· actions · 2024-Apr-28 5:03 pm ·


DadeMurphy
Premium Member
join:2002-07-25
Danvers, MA

[Networking] Opnsense ipv6 prefix changing at every reboot - Verizon FiOS (2)

DadeMurphy to dmb

Premium Member

2024-Apr-29 11:32 am

to dmb

In Interface Settings do you have "Prevent release" checked in the IPv6 DHCP section? Also have you inserted an LL DUID in the "DHCP Unique Identifier" section?

With those two settings I have not had my prefix change during reboots or even with multiple hour power outages here.

· actions · 2024-Apr-29 11:32 am ·

dmb
join:2002-12-03
Morristown, NJ

dmb

Member

2024-Apr-29 11:48 am

said by DadeMurphy:

In Interface Settings do you have "Prevent release" checked in the IPv6 DHCP section? Also have you inserted an LL DUID in the "DHCP Unique Identifier" section?

With those two settings I have not had my prefix change during reboots or even with multiple hour power outages here.

Awesome, I think this may be it, I didn't think to look in global interface settings, was only looking at WAN/LAN interface settings. Prevent release was not checked, and unique identifier was not set (so maybe DUID was changing at every reboot)

· actions · 2024-Apr-29 11:48 am ·


DadeMurphy
Premium Member
join:2002-07-25
Danvers, MA

[Networking] Opnsense ipv6 prefix changing at every reboot - Verizon FiOS (5)

DadeMurphy

Premium Member

2024-Apr-29 11:49 am

Keep in mind the changes require an interface reconfigure or router reboot so you may need to do your dance with the clients one more time after setting this up but I'd expect things to be nice and stable for you after that.

· actions · 2024-Apr-29 11:49 am ·

dmb
join:2002-12-03
Morristown, NJ

dmb

Member

2024-Apr-29 11:51 am

yeah, fun stuff. What makes it real fun is that I have multiple switches in the house, so have to cycle them (or go into every device and reboot manually). But thanks, i would never have thought to look in settings there.

· actions · 2024-Apr-29 11:51 am ·

[Networking] Opnsense ipv6 prefix changing at every reboot - Verizon FiOS (2024)
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