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New Member

Cisco 677 and packet collision on small LAN


I have a problem and a question. The problem is that in my local network, I have a 677 router working an ADSL connection, and behind that a simple dual-speed hub, which connects the LAN to the router. When only one PC is connected to the hub, it generates a heck of a lot of packet collisions - on its own. I find it strange and baffling. Any thoughts?

My question, which may be connected to the problem above, pertains to port forwarding in the router. If I would like to run an FTP server on a certain machine on the network, do I forward all requests from port 20/21 to only this machine's local IP, or do I forward them to every PC? (That goes for any port, that I would like to forward, by the way.) If so, how do I do that in the CBOS, without having to explicitly name every IP address on the LAN? Is there an argument that I can use instead of the local IP that means "all local IP addresses on the network"? What would happen, if I had two FTP servers on my network, and I forwarded inbound FTP requests to them both?

Thanks for any help you can supply.

Best regards,

A. Netherclift,

Copenhagen, Denmark.

New Member

Re: Cisco 677 and packet collision on small LAN

Problem 1

Excessive collisions -

Problem might be in autosensing of Hub for 10/100 or in the NIC of the PC. Mostly probably in the NIC of the PC.

Problem 2

The following command is used in Cisco 675 router to solve the ftp server configuring. check this command is supported in Cisco 677 router also.

Type set nat entry add, followed by these arguments:

inside IP address

inside port number

outside IP address

outside port number


In this example, assume the private address of your server is and the public/routed address assigned to your Cisco 675 is

For example, if you're running a Web server, you would enter:

set nat entry add 80 80 tcp

If you're running an FTP server, you would enter one of the following:

set nat entry add 20 20 tcp


set nat entry add 21 21 tcp