Packet loss at routing to own machine!
I have following test configuration to measure udp round trip time:
|--------|
|---------|eth1 (192.168.1.2)<---->(192.168.1.1) eth1|router 1|eth0
(192.168.3.1)<-
|Test PC | cross cable 1 |--------|
|
|reflect. |
cross |
| |
cable 3 |
|send/rec.| |--------|
|
|---------|eth0 (192.168.2.2)<---->(192.168.2.1) eth1|router 2|eth1
(192.168.3.2)<-
cross cable 2 |--------|
The linux routers 1 and 2 have activated forwarding.
On the Test PC is running an udp Sender program, which sends udp packets
from
eth0 (192.168.2.2) over the routers 2 and 1 to eth1 (192.168.1.2) on the
Test PC.
An udp reflector program receiving the packets on eth1 sends it back
over both
routers to eth0 where the packets arrive.
With etheral it can be seen, that the reflected packets arrive at eth0
of the
Test PC, but the receive call of the send/receive program does not get
the packets.
When the Sender program and the reflector program run on separate
machines,
it works fine.
To avoid an internal shortcut,
(udp packets sent from eth0 to eth1 over the loop back interface)
I shut down the loop back interface with
ifconfig lo down
Following routing table entries were set:
route add -host 192.168.1.1 dev eth1
route add -host 192.168.2.2 gw 192.168.1.1 dev eth1
route add -host 192.168.2.1 dev eth0
route add -host 192.168.1.2 gw 192.168.2.1 dev eth0
All other routing entries were deleted.
Who throws away the received udp packets, when the send/receive program
and the reflector program runs on the same machine ?
Have I to set iptables rules, if so, which rules have I to use ?
Thanks in advance for your help....
