# IPv6 unexpected dual temporary addresses



## epopen (Jan 11, 2022)

Hi All.

My FreeBSD box using dual stack IPv6 with Privacy Extensions (net.inet6.ip6.use_tempaddr: 1) @ WAN NIC example below

```
inet6 OLD prefixlen 64 deprecated autoconf temporary
inet6 1ST_NEW prefixlen 64 autoconf temporary
```
And filter out 1ST_NEW IPv6 address and feed into DNS server by dns/ddclient with scan WAN NIC per 5 minutes periodically and filter condition as below
`/usr/bin/sed -e '/temporary/\!d ;/deprecated/d'`

A day, my FreeBSD box can not access from internet by IPv6.
And checked WAN NIC as below.

```
inet6 OLD prefixlen 64 deprecated autoconf temporary
inet6 1ST_NEW prefixlen 64 autoconf temporary  <- Ping NG from internet
inet6 2ND_NEW prefixlen 64 autoconf temporary <- Ping OK from internet
```
Unexpected dual temporary addresses found.
No idea how to fix, fixed by reboot.

Root cause is dns/ddclient filter out *1ST_NEW* of NG address and access failed from internet  .

Question:

Only one temporary addresses per NIC I think.
But dual exist in my case, something wrong?
Temporary addresses generate in kernel known.
Possible trigger / add hook to notify and pass valid address to  user space application/script like dns/ddclient when valid address available?
Thanks a lot.
Neko


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## epopen (Jan 25, 2022)

Hi All.

Update: Today new weird IPv6 address found as below

```
inet6 2001:b011:a480:40a0:8043:e654:7b55:d566 prefixlen 64 detached autoconf temporary
        inet6 2001:b011:a480:4a6e:8043:e654:7b55:d566 prefixlen 64 autoconf temporary
        inet6 2001:b011:a480:42ee:8043:e654:7b55:d566 prefixlen 64 autoconf temporary
```
Not only dual temporary addresses but also *detached* marked address, both can not ping 

Thanks a lot.


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