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Message 1 of 5

Unexpected IPV6 behaviour

Hi, I have just changed my BTSmartHub out for a Vigor 2862 and have found an unexpected behaviour with BT Infinity IPV6 and wonder if anyone can explain or even confirm this as it had me going round in circles until I found out what was happening.

The Vigor 2862 (no wifi) setup easily and works very well with my BTInfinity FTTC, I have my home network on port 1 and to get seperation from my wifi AP I put the wifi on port 2 and use port based vlans so port 1 and 2 can't communicate.  While testiing I found if my computer was connected to ethernet on port 1 I got a /64 ipv6 prefix perfectly ok and for this purpose just supose it was...

When I disbale the ethernet connection and change to wifi I get a different sub net IPV6 /64 prefix...


To confirm this I made port 3 on the Vigor also a seperate vlan and if I connected through that port I got another ipV6 sub net...


IPV4 stayed the same on all three ports.

So it looks to me as though I am effectivly getting IPV6 subnetting on the different ports of the Vigor.


I am MORE than happy with this but wonder if anyone else has noticed this behaviour, obviously a BTSmartHub doesn't behave like this as it doesn't have port based vlans.

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Message 2 of 5

Re: Unexpected IPV6 behaviour

Welcome to the forum.

That behaviour is perfectly normal.  The /56 prefix allocated by BT gives you 256 /64 subnets.

Message 3 of 5

Re: Unexpected IPV6 behaviour

Thanks Liam :), that's interesting as before I always though BT gave me a /64 but that was when I used the BTSmartHub and persumably that can't use them all (or not that I found) so it was only when I got the Vigor that I noticed this 🙂

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Message 4 of 5

Re: Unexpected IPV6 behaviour

IPv6 can make for interesting reading.  The number of addresses involved is astronomical.  One example being that apparently a /64 equates to a possible 18,446,744,073,709,551,616 individual IP addresses.

So I think most folks would run out of storage space before addresses.

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Message 5 of 5

Re: Unexpected IPV6 behaviour

Yes with a /64 we all have more IPV6 addresses that the whole internet has IPV4 addresses - mind boggling 🙂

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