[SOLVED] How to IPv6 on multiple LANS? Track interface only supports one.

router_wang

What do you do when you have multiple LAN's (LAN/WIFI/KIDS/WIFI_GUEST) and "track interface" is used on LAN, but you want to use IPv6 on other networks?

Derelict

You need a larger prefix delegation from your ISP. The available networks for track interface will be automatically adjusted based on the size of delegation received.

![Screen Shot 2018-04-01 at 11.13.19 AM.png](/public/imported_attachments/1/Screen Shot 2018-04-01 at 11.13.19 AM.png)
![Screen Shot 2018-04-01 at 11.13.19 AM.png_thumb](/public/imported_attachments/1/Screen Shot 2018-04-01 at 11.13.19 AM.png_thumb)

router_wang

@Derelict:

You need a larger prefix delegation from your ISP.

This seems REALLY ridiculous to me. I have a /64 Which is 18 quintillion addresses (18billion*billion), and somehow I need MORE addresses to use a couple more networks. Does this sound completely bat$#1^ crazy to anyone else?

To clarify, I'm not saying you're crazy, just the notion of needing more IPv6 subnets to do this is crazy.

JKnott

@router_wang:

What do you do when you have multiple LAN's (LAN/WIFI/KIDS/WIFI_GUEST) and "track interface" is used on LAN, but you want to use IPv6 on other networks?

As mentioned by Derelict, you need a prefix that's larger than a single /64. I have a /56, which provides 256 /64s. Then when you create a LAN interface, you again track the WAN interface, but also select an IPv6 Prefix ID, to chose which of the /64s to use on that interface.

This seems REALLY ridiculous to me. I have a /64 Which is 18 quintillion addresses (18billion*billion), and somehow I need MORE addresses to use a couple more networks. Does this sound completely bat$#1^ crazy to anyone else?

The reason for this is the method used to automatically assign addresses. With SLAAC, the MAC address is used to provide 64 bits of the device address. It supports both 64 bit MACs and 48 bit, by inserting FFFE in the middle. If you use some other means, such as DHCPv6 or manual configuration, you could get by with a smaller prefix, but it's not recommended.

SLAAC
https://en.wikipedia.org/wiki/IPv6#Stateless_address_autoconfiguration_.28SLAAC.29

router_wang

Ah, it looks like I get a /60 so I got to go figure out prefix delegation and get it working.

Derelict

Do not think of an IPv6 prefix in terms of the number of addresses on a subnet. That is always /64.

Think of it in terms of the number of /64 networks you have available to use on interfaces.

/48 = 65536 /64s or 256 /56s for routing, delegation.
/56 = 256 /64s
/60 = 16 /64s

You can call it ridiculous all you want. It is the way IPv6 is designed. Embrace it knowing you never ever ever have to worry about subnet size again.