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Date: Wed, 7 Jan 2009 15:15:02 +1100 (EST)
From: Ian Smith <smithi@nimnet.asn.au>
To: perryh@pluto.rain.com
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Cc: freebsd-net@freebsd.org
Subject: Re: (partly) SOLVED: tun0 not responding to ping
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On Sun, 4 Jan 2009, perryh@pluto.rain.com wrote:
 > Ian Smith <nimnet.asn.au!smithi@agora.rdrop.com> wrote:
 > > On Fri, 2 Jan 2009, perryh@pluto.rain.com wrote:
 > >
 > >  > Why would a local interface, reported as up in ifconfig, not respond
 > >  > to a ping of its own IP address?  The tun0 reported below doesn't,
 > ...
 > >  >   $ ifconfig -a
 > ...
 > >  >   tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1412
 > >  >           inet6 fe80::2b0:d0ff:fe28:ad4f%tun0 prefixlen 64 scopeid 0x4
 > >  >           inet ZZZ.ZZZ.233.42 --> ZZZ.ZZZ.233.42 netmask 0xffffffff
 > >  >           Opened by PID 24635
 > >
 > > I don't know if this is relevant or not, but I've never seen a point to 
 > > point interface use the same IP address on both ends of its link before.

.. at least, not when using ppp(8)  That's what I get for ASSuming :)

 > It turns out to be normal -- or at least tolerable -- for a tun(4)
 > interface used by vpnc to have the same IP address at both ends.
 > It started working when I added
 > 
 >   NAT Traversal Mode cisco-udp
 > 
 > to vpnc.conf.  (Presumably not all configurations of the Cisco 3000
 > will need that, else it would be the default, but it seems to be
 > correct for the one involved here.)
 > 
 > I never did figure out why that kept the interface from responding
 > to a ping of its own address :(

Glad to hear it's working anyway, on getting back from a few days away.

cheers, Ian