Rare project developers

[Alexander Gall <>]

On Wed, 5 Oct 2022 16:53:49 +0200, Carmen Misa Moreira 
<> said:

> Hi,
> I'm doing some tests and I can only can generate traffic in way direction 
> and not in the other:

> [root@m1~]# iperf3 -c 2001:67c:2c4:1::4

>     [  5] local 2001:1458:301:cd::100:3d8 port 48550 connected to 
> 2001:67c:2c4:1::4 port 5201
>     [ ID] Interval           Transfer     Bitrate         Retr  Cwnd
>     [  5]   0.00-1.00   sec  1.06 GBytes  9.12 Gbits/sec  1370   1.06 MBytes
>     [  5]   1.00-2.00   sec  1.06 GBytes  9.14 Gbits/sec  188   1.46 MBytes
>     [  5]   2.00-3.00   sec  1.07 GBytes  9.17 Gbits/sec  374   1.29 MBytes
>     [  5]   3.00-4.00   sec  1.06 GBytes  9.13 Gbits/sec   24   1.71 MBytes
   
> [root@m1~]# iperf3 -c 2001:67c:2c4:1::4 -R

>     Connecting to host 2001:67c:2c4:1::4, port 5201
>     Reverse mode, remote host 2001:67c:2c4:1::4 is sending
>     [  5] local 2001:1458:301:cd::100:3d8 port 59874 connected to 
> 2001:67c:2c4:1::4 port 5201
>     [ ID] Interval           Transfer     Bitrate
>     [  5]   0.00-1.00   sec  0.00 Bytes  0.00 bits/sec
>     [  5]   1.00-2.00   sec  0.00 Bytes  0.00 bits/sec
>     [  5]   2.00-3.00   sec  0.00 Bytes  0.00 bits/sec
>     [  5]   3.00-4.00   sec  0.00 Bytes  0.00 bits/sec
   
> We connected directly to the routers on both sides of the P4 switch so the 
> VLANs don't pass through the P4 switch and iperf3 works in both
> directions so probably something is going wrong here. Any idea?

Did you check for MTU mismatches along the non-working path? To test
this hypothesis, you can use the -M option to reduce the MSS that
iperf will use to a value that you're sure should work (i.e. 1220 or
lower).

--
Alex

> We are using pure layer 2 bridges on the P4 switch.

> Thanks for your time,

> Carmen Misa