Subject: Re: Recent ipv6 changes and gif breakage
To: None <>
From: Rui Paulo <>
List: tech-net
Date: 01/25/2006 21:36:29

Martijn van Buul <> writes:

> Hello
> The recent changes to the IPv6 stack seems to have killed my gif tunnel.
> Although I'm not 100% convinced that my slightly odd configuration[1]
> plays no role, I don't think it's the major issue.
> What happens is that I do see traffic coming *into* the tunnel as well
> as traffic going *out* of the tunnel, but that neighbour discovery seems
> to go very wrong. My tunnel endpoint (2001:610:1108:5001::3f) is doing
> a neighbour request for the remote endpoint (2001:610:1108:5001::3e), but
> there's no response.  Likewise, I see 2001:610:1108:5001::3e asking for
> 2001:610:1008:5001::3f, but ::3f isn't responding.
> This means that if I do a tcpdump on gif0, and ping a known to be working
> machine on the outside, I can see my ping requests pass by. If I do a tcpdump
> on the external interface of my machine, I see them as well. But there's no
> response. Likewise, if I try to ping my endpoint (or a machine in my 
> allocated range) from the outside, I can see the ping requests arrive at my
> host (both on gif0 and the external interface), but nothing is being
> transmitted back.

Just wondering, can you show your routing entries ?

> Any suggestions would be welcome. I might be able to convince the system
> administration of my tunnel endpoint to do some diagnostics on their side of
> the tunnel, if that would be helpful.
> For the record, my ifconfig:
> 	capabilities=3d80<TSO4,IP4CSUM_Rx,TCP4CSUM_Rx,TCP4CSUM_Tx,UDP4CSUM_Rx,UDP4CSUM_Tx>
> 	enabled=0
> 	address: 00:40:f4:ce:5b:43
> 	media: Ethernet autoselect (1000baseT full-duplex)
> 	status: active
> 	inet netmask 0xffffff80 broadcast
> 	inet6 fe80::240:f4ff:fece:5b43%re0 prefixlen 64 scopeid 0x1
> 	inet6 2001:610:1108:5220:8000::1 prefixlen 65
> 	ssid pienjo nwkey *****
> 	powersave off
> 	bssid 00:0c:f6:18:7f:0e chan 2
> 	address: 00:0c:f6:18:7f:0e
> 	media: IEEE802.11 autoselect hostap (autoselect mode 11b hostap)
> 	status: active
> 	inet netmask 0xffffff80 broadcast
> 	inet6 fe80::20c:f6ff:fe18:7f0e%ral0 prefixlen 64 scopeid 0x2
> 	inet6 2001:610:1108:5220::1 prefixlen 65
> 	address: 00:50:fc:f0:60:58
> 	media: Ethernet autoselect (100baseTX full-duplex)
> 	status: active
> 	inet netmask 0xffffff00 broadcast
> 	inet6 fe80::250:fcff:fef0:6058%rtk0 prefixlen 64 scopeid 0x3
> lo0: flags=8009<UP,LOOPBACK,MULTICAST> mtu 33648
> 	inet netmask 0xff000000
> 	inet alias netmask 0xff000000
> 	inet6 ::1 prefixlen 128
> 	inet6 fe80::1%lo0 prefixlen 64 scopeid 0x4
> 	inet6 2001:610:1108:5220:250:fcff:fef0:6058 prefixlen 64
> gif0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1280
> 	tunnel inet -->
> 	inet6 2001:610:1108:5001::3f ->  prefixlen 64
> 	inet6 fe80::240:f4ff:fece:5b43%gif0 ->  prefixlen 64 scopeid 0x5
> Default IPv6 route is 2001:610:1108:510::3e, default IPv4 route is
> And yes, I know that this is a private address, but no, I can't
> change it.

I tested gif using Freenet6 and I'm behind NAT, so this shouldn't be a

Rui Paulo -