#247 iperf219 without % is not printing output

[Fernando Suarez Ornani]

iPerf 2.1.n (19 March 2023) pthreads
Doing a:
./iperf2.1.9 -s -u -B 239.1.1.3 -p 10000 -i 1 -e
shows only:

------------------------------------------------------------
Server listening on UDP port 10000 with pid 24160
Joining multicast group  239.1.1.3
Read buffer size: 1.44 KByte (Dist bin width= 183 Byte)
Server set to single client traffic mode (per multicast receive)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------

But doing it with %ens6, like:
./iperf2.1.9 -s -u -B 239.1.1.3%ens6 -p 10000 -i 1 -e
shows:

------------------------------------------------------------
Server listening on UDP port 10000 with pid 25460
Joining multicast (*,G)=*,239.1.1.3 w/iface ens6
Read buffer size: 1.44 KByte (Dist bin width= 183 Byte)
Server set to single client traffic mode (per multicast receive)
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  1] local 239.1.1.3%ens6 port 10000 connected with 172.41.21.140 port 34090 (sock=3) (peer 2.1.10-master) on 2023-03-20 18:26:19.154 (UTC)
[ ID] Interval        Transfer     Bandwidth        Jitter   Lost/Total  Latency avg/min/max/stdev PPS NetPwr
[  1] 0.00-1.00 sec   129 KBytes  1.06 Mbits/sec   0.016 ms 30937/31027 (1e+02%) 0.191/0.161/0.384/0.031 ms 91 pps 693
[  1] 1.00-2.00 sec   128 KBytes  1.05 Mbits/sec   0.017 ms 0/89 (0%) 0.197/0.165/0.351/0.030 ms 89 pps 666
[  1] 2.00-3.00 sec   128 KBytes  1.05 Mbits/sec   0.011 ms 0/89 (0%) 0.184/0.164/0.376/0.025 ms 89 pps 713
[  1] 3.00-4.00 sec   128 KBytes  1.05 Mbits/sec   0.013 ms 0/89 (0%) 0.188/0.165/0.317/0.019 ms 89 pps 696
[  1] 4.00-5.00 sec   128 KBytes  1.05 Mbits/sec   0.013 ms 0/89 (0%) 0.189/0.169/0.319/0.017 ms 89 pps 694

On both cases traffic seems to be getting to the thestination (checked with our own tool that monitors traffic).

[Robert McMahon]

can you provide the output from netstat -gn? Also, please check firewall rules that could be blocking multicast.

[Fernando Suarez Ornani]

On the machine with iperf -c:

ubuntu@VML911:~$ netstat -gn
IPv6/IPv4 Group Memberships
Interface       RefCnt Group
--------------- ------ ---------------------
lo              1      224.0.0.251
lo              1      224.0.0.1
ens5            2      224.0.1.129
ens5            1      224.0.0.251
ens5            1      224.0.0.1
ens6            1      224.0.0.251
ens6            1      224.0.0.1
swxtch-tun      1      224.0.1.129
swxtch-tun      1      224.0.0.251
swxtch-tun      1      224.0.0.1
lo              1      ff02::fb
lo              1      ff02::1
lo              1      ff01::1
ens5            1      ff02::fb
ens5            1      ff02::1:ff16:4a15
ens5            2      ff02::1
ens5            1      ff01::1
ens6            1      ff02::fb
ens6            1      ff02::1:ff58:c545
ens6            2      ff02::1
ens6            1      ff01::1
swxtch-tun0     1      ff02::1
swxtch-tun0     1      ff01::1

On the machine with iperf -s:

ubuntu@VML912:~$  netstat -gn
IPv6/IPv4 Group Memberships
Interface       RefCnt Group
--------------- ------ ---------------------
lo              1      224.0.0.251
lo              1      224.0.0.1
ens5            1      224.0.0.251
ens5            2      224.0.1.129
ens5            1      224.0.0.1
ens6            1      239.1.1.3
ens6            2      224.0.0.251
ens6            1      224.0.1.129
ens6            1      224.0.0.1
lo              1      ff02::fb
lo              1      ff02::1
lo              1      ff01::1
ens5            1      ff02::fb
ens5            1      ff02::1:ff7e:f70d
ens5            2      ff02::1
ens5            1      ff01::1
ens6            1      ff02::fb
ens6            1      ff02::1:ff98:d88f
ens6            2      ff02::1
ens6            1      ff01::1

It doesn't seems to be a firewall problem because no matter if I use the % or not, our tool detect that traffic is getting to the destination.

[Robert McMahon]

Is the issue that there are no packets received by the iperf server unless the device interface is specified?

Is the netstat -gn from the command with the device specifier or without?

[Fernando Suarez Ornani]

Is the issue that there are no packets received by the iperf server unless the device interface is specified?

I think that packets are received but iPerf is not showing output. Is this possible?

Is the netstat -gn from the command with the device specifier or without?

I just used nestat -gn and nothing else, without any extra parameter.

[Robert McMahon]

I wanted to know netstat -gn for both cases, with the device specifier on the iperf server and without it. I think you're saying that iperf server only receives multicast only when the device specifier is set. The -gn will show if the socket is open for multicast reception or not. Hence, I need it twice, first when & while packets are recevied and second when they're expected to be received but aren't.