Use One of Dual ISP's


2009-02-13 14:02:21

In a small office I have Comcast Cable and have recently purchased AT&T DSL. Both ISP's will be active. I want SmartFTP on one PC to use AT&T, the other PC's to use Comcast, and all PC's to see each other on the network.

Why do this? When SmartFTP is uploading large files via Comcast Cable, latency becomes a problem. Pinging the Comcast dsn server shows response time increasing from 4ms to 350ms. Plus Comcast is unreliable with outages now and then. When this occurs I intend to use the AT&T dls to provide an ISP for all PC's. Since the AT&T dsl will be mostly for backup I want to use it for SmartFTP uploads and avoid affecting Comcast response times.

Now the question is how to configure the network to accomplish what I want. I've bogged down with too many possibilities. Any advice is greatly appreciated.


Office has 5 PC's all running Windows XP Pro in a peer-to-peer network, joined with a Gigabit switch and connected to Comcast via a router and cable modem.

The PC running SmartFTP has two NIC's. NIC-A is currently cabled to the switch that is on the office network and Comcast. NIC-B is not yet connected. This PC is used like a file server on the office peer-to-peer network, runs nightly 5GB backups that are uploaded via SmartFTP, and is accessed via the Internet using XP Remote Desktop Connection (RDC).


1) Connect NIC-B to the dsl modem and set up a PPOE dialup in Internet Connections, configured to always dial a connection. Perhaps SmartFTP will use this connection?

Since we have spare equipment, NIC-B could be connected to the dsl modem via a router if that offered any advantages. The next two possibilities use both routers.

2) Connect NIC-B to a router on a different subnet and connect the two routers (Comcast and AT&T), disabling NIC-A. SmartFTP would use the AT&T router for uploads and RDC sessions would use the Comcast router and then connect to the PC via the AT&T router?

3) Connect NIC-B to a router on a different subnet and connect the two routers (Comcast and AT&T), leaving NIC-A connected to the Comcast router. Somehow tell SmartFTP to use the AT&T router for uploads and RDC to use the Comcast router?


2009-02-13 14:11:00

Limit the upload speed. Go to the favorite properties. Then go to the Transfer dialog and set the upload limit.

For a dual WAN setup you need to manually configure the routing table or you can purchase a dual WAN router and set the QoS according to your requirements. But in summary it's not something trivial to setup.



2009-02-13 19:14:14


Thanks for that advice. When I limit the SmartFTP upload speed or even pause the upload I still get lots of latency which shows up as sluggish response time.

If I run it shows that throughput is acceptable (9mbps up, 6mbps down) but latency is a problem with ping times of 300 ms or so. Stopping the SmartFTP upload or closing SmartFTP restores ping times to the 3 to 1 ms range.

Am I missing something in my SmartFTP configuration? Or perhaps is this a Comcast or cable modem issue?


2009-02-13 19:17:10

If you are uploading with the max bandwidth through an asynchronous connection (e.g. ADSL) the behavior you see is normal. A workaround is to limit the upload speed or to upgrade your internet connection. I recommend you talk to your web hosting provider for assistance.