hi!
i´m new to the list, and i don´t know if you have discussed this before or
if this is the place to post this kind of problems (if not, please correct
me) , but it s driving me insane, so here it goes...
i have a Red Hat 7.3 doing nat for an internal net of about 50 PCs.
it is doing so using shorewall (a wrapper for iptables), squid (virtual or
transparent mode) and a few things with iproute2.
I ´ve always had two internet connections, a direct connetion via a Cisco
Router(dont remember its model) and the other over ADSL.
I´d managed to have the two gateways running, using the direct connection
for inbound traffic and as a backup for outbound connections. All the
outbound trafic would go via ADSL, while it was connected and without
problems. If for a reason, the ADSL went down, a script would place the
direct connection as default gateway.
A brief description of IPs ant interfaces:
LAN Gateway(3 NICs) Internet
192.168.1.X
200.10.10.10 eth0 ---------------------------- Cisco
Router---------------------
200.10.10.11 eth0:0
192.168.1.1 eth1
N/A (or a fake one)
-----------------------------ADSL -----------------------------
------------
200.100.100.100 ppp0 ------------------|
The gateway has two external IPs (besides the ppp0 one). One is for
accessing the gateway itself, and the other for accessing an internal server
via DNAT.
All was working properly, but suddenly people who were using the internal
server from outside lost connection with it, even without the posibility of
ping'n it. Weird as it seemed to be working ok from inside.
Here is where im confused.
The ADSL is working ok, because it connects without problems, and NAT can do
its job serving internet for all the local network. But when it is
connected, PCs from outside cannot ping or access IPs binded to eth0 or
eth0:0(alias) and yes, they can ping and access services on ppp0.
If you disconnect the ADSL , and put back the gateway to have the direct
connection all start working ok again (but considering that the traffic on
the Router is higher than we want).
I checked a lot of things without success. The strange thing, leaving aside
the script that handles the changing default gateways (i mean, doing all by
hand), is that if the ADSL is connected but you keep the default gateway to
the Router, it works. The moment you change the DG, it's lost.
I'm sorry about the extension of this, but i couldn't find the way to
describe this using less words. I hope you could understand my english (i
know is bad) and if you need more details i would be more than happy to give
them to you...
i expect eagerly to hear from you all.
Thank You in advance!!!
Santiago Vazquez
Open Computacion S.A.
Buenos Aires
Argentina
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