[Story] When IPv6 Fixes IPv4 Peering Issues

Mon Jun 13 19:07:17 UTC 2022

On 6/13/22 12:22 PM, Jon Lewis wrote:
> On Mon, 13 Jun 2022, Brie wrote:
> 
>> Who knows...  Hard to know if I'm taking a different network path or 
>> just going through the same routers but bypassing whatever is blocking 
>> the packets.
> 
> You might be able to infer that from the hops that show up in traceroutes.

So, I was looking at that, and the lack of rdns on many IPv6 hops is... 
aggravating.  CL/Lumen does embed ipv4 addresses in some of their IPv6 
router addresses, but not all.

So, not really enough to determine really if I am, unfortunately.

> 
>> I went so far as to even randomize source/dest ports on each end in 
>> case it was some sort of misguided filtering (ie:  port 12345 -> 54321 
>> instead of 12345 -> 12345).
> 
> That really makes it odd.  If you tried changing the src/dst ports with 
> v4, and your VPN traffic still would not pass, but iperf would, what 
> kind of filtering/breakage could CL or Comcast have that would just stop 
> your VPN traffic regardless of ports?
> 
> I wonder if this is a misguided/misbhaving filter rule, or something 
> actually broken eating your packets.  Having dealt with something far 
> stranger many years ago, I totally get the aspects of "big telco can't 
> help / won't let you even talk to someone who can understand your 
> explanation of the issue" and "I don't care how I solve this, as long as 
> I can make the issue go away."
> 

One thing I did not think about before reading your response, was the 
size of the UDP packets.  Its possible something's blocking UDP packets 
below a certain size.

iPerf is going to send packets of a consistent size for testing, whereas 
WG is likely to have varying sizes depending on contents of packets.

Maybe I need to do some testing with varying packet sizes.

> 
> ----------------------------------------------------------------------
>   Jon Lewis, MCP :)           |  I route
>   StackPath, Sr. Neteng       |  therefore you are
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-- 
Brielle Bruns
The Summit Open Source Development Group
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