[lug] Cisco 678 and NAT

[Dan Ferris]

I have experience with 2 Cisco 678s.  I think they are the best DSL
modem out there personally.

The best way to use one is to get a seperate router and run them in
bridging mode.  I do that with a Soekris box running m0n0wall and it
NEVER crashes.

Just my $.02

Dan

Ben wrote:

>Probably as karmicly induced punishment for cursing the name of Qwest, my
>work has very unreliable DSL from Qwest. Every now and then it is 1.5mps
>(as spec'd), but it drops down to 640, or 128kps or drop outs completely.
>If it drops to a low speed (128kps), it will stay they until I manually
>reset the connection or until DSL goes down fully. On reset, it might get
>to a higher speed, it might not.
>
>(I've yelled at them for weeks and they claim that there is nothing they
>can do: we are far from the station and the wires going from my work to
>the station are shared with 25 T1's and when the T1's are in use I get
>noise pickup and it drops the DSL connection.)
>
>So what to do? I bought a cisco 678 (I was using their supplied ActionTek)
>and it seems to get slightly higher connection speeds. I also have a
>static ip address. I've got a minicom script that talks to the cisco modem
>and gets its connection speed. I also have a minicom script that runs "set
>int wan0 down" "set int wan0 up" to reset the DSL and allow me to connect
>(potentially) at a higher speed. I've got a little cron job that looks at
>the speed and how long it has been there and decides when to reset the
>DSL. This works fine, in that it now doesn't get hung at low speeds, as it
>will often get bumped down to 400kps for a few minutes, but 10 minutes
>later I can reconnect at (a blazing) 1024kps.
>
>But my problem is with NAT. When I do the reset, the cisco resets all its
>NAT tables and all the people using the internet get their connections
>reset. I'd like to not have this happen, but just have the connections
>pause (though potentially time out, I guess)  Now I've got a netgear
>firewall / router between my intranet and the cisco, so the cisco forwards
>everything to the 10.0.0.2 (the firewall) which does NAT to my intranet
>
>Intranet (192.168.0.0/24) -> 192.168.0.1 (firewall intranet) -> 10.0.0.2
>(firewall outside) -> 10.0.0.1 (cisco wan0 ip) -> static internet IP
>
>I've tried adding the line:
>
>set nat entry add 10.0.0.2
>
>so it forwards everything to 10.0.0.2. But my ssh connections (and
>whatnot) still get upset by the reset. Is there a better way to do this? I
>don't think Qwest supports bridging mode anymore (I'm using pppo[AE] I
>believe).
>
>Any ideas on how to make the best of crummy dsl? As a side note, the
>internet was very slow all day on Jan 1st! This puts some doubt as to the
>problem being the T1's nearby being used, since I know none of our
>neighbors (low-tech shipping companies) were open on Sunday.
>
>Thanks,
>
>Ben
>
>
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