Hi,
Sorry to post only problems,
after this saga I am into, I might became someone able to post
solutions as well,
With Infinite thanks to Jan Engelhardt who has been helping beyond
any imaginable point and getting me closer to the solution,
I have a subnet which needs to connect to a several other subnets
through a T1
for some reason at the other end, a request I initiate to a machine
at 172.16.2.34
generates as well a response from 172.16.1.49 which in turn needs to
trespass the nat
thus the triangulation
I tried from one to one nat, with proxy arping and would fail as well,
could be a hardware problem?
as a hint, when replaced my ipcop by a cheapo dsl router,
the natting to the other subnets worked just fine,
dump from ipcop box shows the following,
I set a rule to allow whatever from 172.16.1.49
root@ipcop:~ # iptables -I CUSTOMINPUT -s 172.16.1.49 -j ACCEPT
Now I dump the relevant (to my opinion)
root@ipcop:~ # tcpdump -i eth2 | grep '172.16'
tcpdump: verbose output suppressed, use -v or -vv for full protocol
decode
listening on eth2, link-type EN10MB (Ethernet), capture size 68 bytes
(here goes the first request)
16:47:06.068643 IP 192.168.50.1.qsm-proxy > 172.16.2.34.ms-sql-m:
UDP, length 7
(now this machine gets in the middle)
16:47:06.072886 IP 172.16.1.49.ms-sql-m > 192.168.50.1.qsm-proxy:
UDP, length 120
16:47:06.073061 arp who-has 172.16.1.49 tell 192.168.50.1
16:47:06.073511 arp reply 172.16.1.49 is-at 00:18:18:c4:96:50 (oui
Unknown)
(since I gave permission to 172.16.1.49 to do whatever, then why is
the already opened port qsm-proxy unreachable?)
16:47:06.073541 IP 192.168.50.1 > 172.16.1.49: ICMP 192.168.50.1 udp
port qsm-proxy unreachable, length 156
(tree more times until it fails)
16:47:09.958188 IP 192.168.50.1.vchat > 172.16.2.34.ms-sql-m: UDP,
length 7
16:47:09.962465 IP 172.16.1.49.ms-sql-m > 192.168.50.1.vchat: UDP,
length 120
16:47:09.962550 IP 192.168.50.1 > 172.16.1.49: ICMP 192.168.50.1 udp
port vchat unreachable, length 156
16:47:11.060699 arp who-has 172.16.2.34 tell 192.168.50.1
16:47:11.061148 arp reply 172.16.2.34 is-at 00:18:18:c4:96:50 (oui
Unknown)
16:47:13.943012 IP 192.168.50.1.tripwire > 172.16.2.34.ms-sql-m: UDP,
length 7
16:47:13.947216 IP 172.16.1.49.ms-sql-m > 192.168.50.1.tripwire: UDP,
length 120
16:47:13.947293 IP 192.168.50.1 > 172.16.1.49: ICMP 192.168.50.1 udp
port tripwire unreachable, length 156
16:47:18.130143 IP 192.168.50.1.indigo-server > 172.16.2.34.ms-sql-m:
UDP, length 7
16:47:18.134375 IP 172.16.1.49.ms-sql-m > 192.168.50.1.indigo-server:
UDP, length 120
16:47:18.134457 IP 192.168.50.1 > 172.16.1.49: ICMP 192.168.50.1 udp
port indigo-server unreachable, length 156
2469 packets captured
2491 packets received by filter
0 packets dropped by kernel
