I solved all my router issues by moving my IPIP gateway offsite and
using a ZeroTier virtual LAN to bridge the remote router to a LAN
segment here. Works well, only adds a few mS latency, but given that
the IPIP network isn't really a high performance network, this is
inconsequential in practice.
On 13/1/25 4:14 pm, Gavin Rogers via 44net wrote:
> Hi Eric.
>
> A shame you're not able to directly connect to your ISP's incoming
> interface, with their modem being a mysterious blackbox it's going to
> be hard. Do you have any controls at all on the ISP modem, perhaps
> features like its VPN passthrough is interfering?
>
> I just did a packet capture for a while from my link, and I'm
> receiving nothing but good traffic from the USCD gateway. (although in
> practice it is incredibly slow here in Australia - less than 1Mbit/sec)
>
> If you need a far-end node to set up some packet captures with or set
> up an iperf node or the like, let me know.
>
> 73
> Gavin
> VK6HGR
>
> On 13/01/2025 12:57 pm, Eric Johnson via 44net wrote:
>> All,
>>
>> I was trying to bring up an AMPRNet IPIP tunnel in my lab network,
>> but when I did a packet capture on the WAN side of the gateway I am
>> setting up, I noticed that on average, about 80% of the IPIP packets
>> I receive from the UCSD gateway have their inner headers corrupted.
>> As far as I can tell, the first 4 bytes of the inner header are being
>> overwritten with a garbage byte sequence (hex 00-04-00-00). I have
>> included a packet capture showing what's going on. At packet 63, the
>> RIP announcement starts, and continues through packet 100, so there's
>> some known-good traffic in there.
>>
>> Has anyone seen anything like this before?
>>
>> I have another AMPRNet IPIP tunnel set up on a datacenter server, and
>> it has no such problem, so this is an isolated issue (i.e., not an
>> issue with the UCSD gateway). The only other thing I could suspect is
>> that the ISP-issued modem/gateway combo unit. Of course, I have no
>> visibility into traffic upstream of this unit, so I don't have a way
>> to know if it is causing the corruption. Unfortunately, my ISP
>> doesn't let me disable the gateway function of the unit, so I have to
>> suspect the firmware of this device.
>>
>> Any and all help is appreciated. I am going to call my ISP tomorrow
>> and see if they are aware of any issues with these modem/gateway units.
>>
>> Thanks,
>> Eric Johnson - AE0JE
>>
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--
73 de Tony VK3JED/VK3IRL
http://vkradio.com
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