IPv6 not working on NBN — how to diagnose and fix it

Why this happens

• The most common cause is the ISP simply not having IPv6 enabled on your account — no amount of router configuration will fix this.
• The router's WAN connection type may be set incorrectly — it needs to be DHCPv6-PD (prefix delegation), the method NBN uses to hand your router a block of IPv6 addresses to share across your home.
• Even if the router has a working IPv6 connection, your devices won't get addresses unless Router Advertisements are enabled — this is the signal your router sends to tell devices that IPv6 is available.
• Your router's software (firmware) may be too old to properly support prefix delegation — an update or replacement may be needed.
• Some router firewalls block ICMPv6 — the signalling traffic IPv6 relies on to announce itself and find other devices. Without it, IPv6 breaks silently even though everything else looks configured correctly.

How to fix it — step by step

1. 1. Confirm your ISP actually provides IPv6

   This is the most common cause. Contact your ISP and ask: "Is IPv6 included on my service?" Many Australian ISPs don't offer it, or haven't enabled it on your specific account. If the answer is no, no router change will help — you need an ISP that includes IPv6.

2. 2. Check the router's WAN IPv6 connection type

   Log into your router's admin panel. The WAN IPv6 mode must be set to DHCPv6-PD (prefix delegation) — this is how your router requests a block of IPv6 addresses from your ISP and shares them across your home network. If it's set to anything else — including SLAAC, Static, or disabled — change it to DHCPv6-PD and save.

3. 3. Check that Router Advertisements are enabled

   Even if the router has a working IPv6 connection, your phones and laptops won't receive addresses unless Router Advertisements (RA) are switched on. Find this in your router's LAN or home network settings — look for "Router Advertisement", "RA", or "SLAAC". Without it, devices will show no IPv6 address even though the router itself has one.

4. 4. Check the router's IPv6 firewall

   Some routers have an aggressive IPv6 firewall that blocks ICMPv6 — the signalling traffic that IPv6 uses for router advertisements and finding other devices on the network. IPv6 cannot work correctly without it. Look for an IPv6 firewall or ICMPv6 setting and make sure ICMPv6 traffic is permitted between the router and your devices.

5. 5. Update your router's software

   Older router firmware sometimes has broken or incomplete prefix delegation support. Check the manufacturer's website for your exact model and install any available update. If no update is available and prefix delegation still won't connect, a router replacement is the most reliable fix.