can't seem to forward ports

Unanswered Question
Aug 3rd, 2007


I'm having problem getting the port forwarding to work. When testing my home router (851w) at work, using VNC, Telnet, SSH, nothing gets through. Cannot connect, so it's not an authentication issue, as I don't reach the username/password stage.

Please take a look at my config and see what the mistakes might be. Also, what is the command to mask the passwords in my configuration? The <password> I've typed in were original just plain text.

I tried to set most of the stuff up with the CLI, and some were helped by SDM.

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Overall Rating: 4 (1 ratings)
royalblues Fri, 08/03/2007 - 20:43


You have configured IP address on the VLAN interface (SVI). To telnet or SSH your SVI should be up.

To bring up this SVI you require atleast one port in vlan 1.

Check by configuring an IP address on the etherner interface and do a telnet. Though you will able to do SSH too, you should look at configuring this way



winstoncheng Sun, 08/05/2007 - 16:08

Hi Narayan,

I don't quite understand how to execute this. If I am to create a SVI interface on the router, I'm not seeing that as a choice under the commands.

Also, is there a way to go about this w/o an IP for VLAN1? I only put that address there because it was the only way to assign an IP to the router itself I could see.

Paolo Bevilacqua Sun, 08/05/2007 - 16:31


for one, you will need to move all the vlan1 config to bvi1 and configure no ip address and bridge-group 1 under vlan1. Else, you will never be able to use your wireless.

Then yes of course you need and IP for BVI1. It's your PC's default gateway address

The port forward seems correct and you should be able to connect from outside, but please remap 23 to something else if you still want to be able to telnet into the router. Finally, you don't need this:

ip nat pool nat1 netmask

Hope this helps, please rate post if it does!

winstoncheng Mon, 08/06/2007 - 06:38

Hmm, well, the wireless is working, but I'm still unable to VNC, telnet, or SSH into my home router from work.

If I PuTTY through telnet the black screen comes up with a "(inactive)" in the title bar.

If I SSH, I get PuTTY Fatal Error, "Network error: Connection refused".

For VNC, which is the forward, "Failed to connect to server".

Paolo Bevilacqua Mon, 08/06/2007 - 07:18

Strange, can you at least telnet into the router ?(require removing the port 23 forward).

Also pls send again the router config now.

winstoncheng Mon, 08/06/2007 - 07:41

I have to wait until I get home to send the router config again, unless I find time during lunch break.

Instead of using 23, i used 2300. I'm able

to telnet from inside the network, but not from outside.

I will also need to double-check and make sure is working so I know I'm not using the wrong IP address.

winstoncheng Mon, 08/06/2007 - 11:12

Apparently I don't know how to designate a different port to telnet yet, so I reverted the port forward lines back to port 23.

And sorry, I forgot to verify if the ddns is working properly or not.

The odd thing is, the 1811w at work I can telnet/SSH to with no problems, and that one doesn't even have the static tcp lines.

Paolo Bevilacqua Mon, 08/06/2007 - 11:47


remove these:

ip nat inside source static tcp 23 interface Dialer0 23

ip nat inside source static tcp 22 interface Dialer0 22

and you should be able to telnet/ssh into router. Regarding the forwards, these should work as configured, not sure why they don't.

winstoncheng Mon, 08/06/2007 - 15:44

Yep, telnet and SSH appears to be working, however, I'm still unable to get VNC going. :(

Paolo Bevilacqua Mon, 08/06/2007 - 17:36

That is, you can telnet and ssh to the router, but no forward to hosts behind the router works ? Can you try something else than VNC for a test? Eg web server to an host behing the router, like port 8000 "outside" mepped to 80 "inside".

winstoncheng Tue, 08/07/2007 - 21:57

Sorry, currently working on upgrading the computer, and the only quick thing I could think of was to run an FTP server. However, the FileZilla Server kept saying it couldn't connect to the local server.

I'll see what else I can try.

winstoncheng Wed, 08/08/2007 - 08:44

OK, when trying this with the LAN at work, I'm able to get FTP to work, but not VNC. Cisco routers just don't like to pass through VNC data?

winstoncheng Wed, 08/08/2007 - 09:32

Not sure if I'm mistaken or not about previous result, but FTP is not currently working. :(

winstoncheng Thu, 08/09/2007 - 06:59

Using online ShieldUp service, all the ports I opened, are indeed open, so the problem appears to be that they aren't being directed to the internal PC's properly.

winstoncheng Thu, 08/09/2007 - 21:57

Still stuck on this. Would this provide any leads?

tcp --- ---

tcp --- ---

tcp --- ---

tcp --- ---












Paolo Bevilacqua Fri, 08/10/2007 - 03:13

It seems the config is correct. I have an 851w and I can forward ports without any problem. I use 12.4(11)XJ4, perhaps you may want to try that image as well.

winstoncheng Fri, 08/10/2007 - 06:21

Hmmm, I only have guest level access, can't seem to grab any software updates.

Paolo Bevilacqua Sat, 08/11/2007 - 05:57

In fact you can't. You will need a support contract, aka smartnet, in order to access the downloads. This should be available from your cisco reseller and the simpler level should be well below $100 forone year, that beside the download include hardware warranty and access to TAC support.

Correction, the IOS the I use is 12.4(11)T2.


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