MacOS pptp client + IPv6

William J Hulley bill.hulley at
Thu Feb 10 16:35:20 CET 2011

On 7 Feb 2011, at 14:31, Simon Perreault wrote:

> On 2011-02-07 09:23, Jared Mauch wrote:
>> Anyone gotten the MacOS PPTP/VPN client to obtain an IPv6 address?  I'm using a Cisco router on the other end, and am looking for anything obvious i'm missing.  It appears to be sending the traffic out the virtual-access interface just fine, but I'm not seeing an IPv6 address on the ppp0 interface.
> Maybe this will be helpful:
> Especially this part:
>> However, the IPv6 global addresses are now shown anywhere, either in the Network Settings Panel, nor with ifconfig ppp0. The IPv6 PPP specification(RFC5072) says that the global address is obtained by router advertisements on the PPP link or by DHCPv6.
>> Inspection of MacOSX shows that router advertisements were not enabled (surprisingly, becauseI'm using IPv6 RA at the office without having to do any change in the kernel config) in the kernel, so I enable them.
>> # sudo sysctl -w net.inet6.ip6.accept_rtadv=1
>> net.inet6.ip6.accept_rtadv: 0 -> 1

I've been using a similar config for a couple of years now,  but with L2TP/IPsec instead of PPTP.

Older versions of Mac OS X needed a ppp up script to add the ipv6 defaut route,  but more 
recently that seems to have been fixed.

Since enabling IPv6 on my office network I've noticed another bug with the v6 default route.

With a IPv6 address and default route on the underlying interface (ethernet, wifi) if I make a v6 
enabled VPN connection to my Cisco at home it gets a v6 address on the ppp interface just fine 
but then it wont install an additional IPv6 default route.   A secondary IPv4 default route to the 
ppp interface is installed as you'd expect with the 'send all traffic over vpn connection' box 

Manually adding a ipv6 default route results with this message:
# route add -inet6 default -interface ppp0
route: writing to routing socket: File exists
add net default: gateway ppp0: File exists

I can remove the ethernet default and then add one via ppp0 but ping6 still wants to bind to the
IPv6 address of the ethernet interface not the ppp interface.

If I take the VPN down, disable IPv6 on the ethernet interface and bring the VPN back up all works
as expected and v6 works fine on the ppp interface.

Any ideas?


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