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Date:      Wed, 12 Nov 2008 15:57:41 -0500
From:      Stephen Clark <sclark46@earthlink.net>
To:        Julian Elischer <julian@elischer.org>
Cc:        freebsd-net@freebsd.org
Subject:   Re: FreeBSD 6.3 gre and traceroute
Message-ID:  <491B4345.80106@earthlink.net>
In-Reply-To: <491B31F7.30200@elischer.org>
References:  <491B2703.4080707@earthlink.net> <491B31F7.30200@elischer.org>

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Julian Elischer wrote:
> Stephen Clark wrote:
>> Hi,
>>
>> When I run traceroute thru a gre it doesn't seem to decrement the
>> ttl, so I get * * * for that hop. Can this be fixed?
>>
>> Thanks,
>> Steve
> 
> you will need to define the setup and question better.
> 
> TTL is controlled by the IP stack which is unaware of which interface
> it came in on and doesn't care which interface it goes out on. That 
> includes GRE interfaces.. Is it freebsd at both ends?
> 
> 
> BTW * * * would come from an EXTRA decrement
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FreeBSD workstation 10.0.129.1<-->10.0.128.1 Freebsd FW "A" with gre over ipsec 
tunnel<---->FreeBSD FW "B" with gre over ipsec tunnel 192.168.3.1<--->
192.168.3.86 linux workstation

$ sudo traceroute 192.168.3.86
traceroute to 192.168.3.86 (192.168.3.86), 64 hops max, 40 byte packets
  1  HQFirewallRS.com (10.0.128.1)  0.575 ms  0.423 ms  0.173 ms
  2  * * *
  3  192.168.3.86 (192.168.3.86)  47.972 ms  45.174 ms  49.968 ms

No response from the FreeBSD "B" box.

When I do a tcpdump on "B" of the gre interface I see UDP packets
with a TTL of 1 but no ICMP repsonse packets being sent back.

If I do the traceroute from the linux workstation 192.168.3.86 I get
similar results - I don't see a response from the FreeBSD "A" box.

Regards,
Steve
-- 

"They that give up essential liberty to obtain temporary safety,
deserve neither liberty nor safety."  (Ben Franklin)

"The course of history shows that as a government grows, liberty
decreases."  (Thomas Jefferson)





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