Could this be relevant to your case?
http://www.embedded-bits.co.uk/2008/multiple-network-gotcha/
2012/12/9 Martin T <m4rtn...@gmail.com>:
> Hello,
>
> I have a following simple network topology consisting of two laptops
> and one L2 switch facing with trunk ports to laptops:
>
> T60[eth0] <-> switch <-> [eth0]T42
>
>
> Both T60 and T42 machines have three sub-interfaces:
>
>
> T60:~ # ip addr show | grep "eth0.[0-9]*$"
> inet 10.10.1.1/24 brd 10.10.1.255 scope global eth0.534
> inet 10.10.2.1/24 brd 10.10.2.255 scope global eth0.541
> inet 10.10.3.1/24 brd 10.10.3.255 scope global eth0.653
> T60:~ #
>
> T42 ~ # ip addr show | grep "eth0.[0-9]*$"
> inet 10.10.1.2/24 brd 10.10.1.255 scope global eth0.534
> inet 10.10.2.2/24 brd 10.10.2.255 scope global eth0.541
> inet 10.10.3.2/24 brd 10.10.3.255 scope global eth0.653
> T42 ~ #
>
>
> ..and L3 connectivity between laptops works fine:
>
>
> T60:~ # ping -I 10.10.1.1 -qc10 10.10.1.2
> PING 10.10.1.2 (10.10.1.2) from 10.10.1.1 : 56(84) bytes of data.
>
> --- 10.10.1.2 ping statistics ---
> 10 packets transmitted, 10 received, 0% packet loss, time 8999ms
> rtt min/avg/max/mdev = 0.271/0.349/0.436/0.047 ms
> T60:~ # ping -I 10.10.2.1 -qc10 10.10.2.2
> PING 10.10.2.2 (10.10.2.2) from 10.10.2.1 : 56(84) bytes of data.
>
> --- 10.10.2.2 ping statistics ---
> 10 packets transmitted, 10 received, 0% packet loss, time 8999ms
> rtt min/avg/max/mdev = 0.250/0.349/0.427/0.048 ms
> T60:~ # ping -I 10.10.3.1 -qc10 10.10.3.2
> PING 10.10.3.2 (10.10.3.2) from 10.10.3.1 : 56(84) bytes of data.
>
> --- 10.10.3.2 ping statistics ---
> 10 packets transmitted, 10 received, 0% packet loss, time 8997ms
> rtt min/avg/max/mdev = 0.271/0.359/0.404/0.043 ms
> T60:~ #
>
>
> Both T60 and T42 have firewall disabled.
>
> I started three Iperf server processes in T60 with "iperf -s -u -fm -B
> 10.10.1.1 -p 5001", "iperf -s -u -fm -B 10.10.2.1 -p 5002" and "iperf
> -s -u -fm -B 10.10.3.1 -p 5003" commands:
>
>
> Proto Recv-Q Send-Q Local Address Foreign Address
> State PID/Program name
> udp 0 0 10.10.1.1:5001 0.0.0.0:*
> 6026/iperf
> udp 0 0 10.10.2.1:5002 0.0.0.0:*
> 5867/iperf
> udp 0 0 10.10.3.1:5003 0.0.0.0:*
> 5870/iperf
>
> Now if I start Iperf clients in T42 machine with "iperf -c 10.10.1.1
> -fm -t20 -u -b 20m -p 5001", "iperf -c 10.10.2.1 -u -d -fm -t 120 -p
> 5002" and "iperf -c 10.10.3.1 -u -d -fm -t 120 -p 5003" commands, the
> server processes do not indicate that there has been a connection from
> Iperf client. Iperf clients just indicate that there was no ack
> received of the last datagram:
>
> [ 3] Sent 34015 datagrams
> [ 3] WARNING: did not receive ack of last datagram after 10 tries.
>
>
> For example if I execute "nmap -PN -sU -p 5001 --reason 10.10.1.1" in
> T42 I can see that Iperf server with PID 6026("iperf -s -u -fm -B
> 10.10.1.1 -p 5001") receives a connection. In addition, if I run
> "tcpdump -ni eth0.534 udp and port 5001" in T60 machine and execute
> "iperf -c 10.10.1.1 -fm -d -t20 -u -b 20m -p 5001", then I capture
> nothing with tcpdump.
>
> Iperf version both in T42 and T60 is 2.0.5. Any ideas what might cause
> such behavior? In case additional information is needed, please ask.
>
>
>
> regards,
> Martin
>
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