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Old 06-22-2004, 12:09 PM   #1
dcgva
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Registered: Feb 2004
Location: Geneva
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Unable to forward with multiple network cards


I'm trying to setup a router between 4 networks. Last week I managed to make it work with three networks, but since I added another network card, it doesn't seem to work anymore. I'm certainly doing something wrong but I realseely don't see what...

Here is the configuration of my test (let's drop the two additional net)

A <-- NET X --> B <-- NET Y --> C

NET X on system A : 192.168.1.10
NET X on system B : 192.168.1.70
NET Y on system B : 192.6.1.60
NET Y on system C : 192.6.1.20

Routing is properly defined on system B, as well as C & D.
IP forwarding is also set on system B (/proc/sys/net/ipv4/ip_forward as well as for all other individual cards .../conf/eth*/forwarding).

From system A, I can ping 192.1.6.60 and system C can ping 192.168.1.70. However, system A & B can't ping to each other. When pinging A from C, a tcpdump on NET X card of system B shows all request comming through. However, doing a tcpdump on another system plugged on NET X doesn't show anything at all !

I believe that all IP packets are not forwarded on system B; eventhough I have the forwarding setup. What's the problem ? That's a real mistery... Is there a problem with the number of cards ? Or, do I need to something else ? I don't see what I can do investigate where these packets get blocked...

Any ideas ?
 
Old 06-22-2004, 01:47 PM   #2
maxut
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Location: istanbul
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is there any firewall on B ? maybe it blocks requests.

check routing table and iptables.
route -n
iptables -nvL
iptables -t nat -nvL

or just stop iptables.
 
Old 06-22-2004, 02:38 PM   #3
dcgva
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No, There is no firewall.

the result of 'iptables -t nat -nvL' is :

mjtlnx3:/home/dc # iptables -t nat -nvL
Chain PREROUTING (policy ACCEPT 1566 packets, 108K bytes)
pkts bytes target prot opt in out source destination
1510 104K all -- * * 0.0.0.0/0 0.0.0.0/0

Chain POSTROUTING (policy ACCEPT 505 packets, 30692 bytes)
pkts bytes target prot opt in out source destination

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination

Rather strange... I can ping any network from system B. Since I have the following routing table :


mjtlnx3:/home/dc # route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
194.209.241.0 mjtlnx3.mjt.ch 255.255.255.0 UG 0 0 0 eth3
192.168.1.0 192.168.1.70 255.255.255.0 UG 0 0 0 eth0
194.88.9.0 194.88.9.27 255.255.255.0 UG 0 0 0 eth1
192.6.1.0 mjtlnx3.hesse.m 255.255.255.0 UG 0 0 0 eth2
link-local * 255.255.0.0 U 0 0 0 eth1
loopback * 255.0.0.0 U 0 0 0 lo
default cisco.mjt.ch 0.0.0.0 UG 0 0 0 eth3

ping issued from system B would also be blocked. No ?

Would the POSTROUTING queue tell me something ?
 
  


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