NAT/PAT telnet question.

I finally got my lab constructed and have been having a blast setting it up and actually getting to keep up with Chris Bryants Trainsignal videos.

Now I want to be able to telnet in and play when I'm away (I have one of those APC UPS's that let you power on devices remotely, which would scare the crap out of the kids, esp the 3640's) but then I realized I have no idea how to hook that up properly.

I do not have an 2509/2511 access server yet so I just need to hook up one for now.

This seems like one of the most basic things I should know but it isn't talked about in the videos I have, he just assumes a telnet connection often.

So I thought maybe if I just grabbed a CAT-5 and connected my home router to the installed WIC-1B-U then that should give me connectivity (I really don't know much about modules...ugh). However, even if that's how it works what IP would I telnet to? So then I thought of connecting my cable modem directly and getting an assigned IP from my provider might be easier.

But it shouldn't have to be! I should know how to do this! Now I am resolved to figure this out and after thinking for awhile I came to the conclusion that I just don't understand how NAT and PAT really work. It was only briefly touched on during the CCENT1 DVD and I don't see much of it on the next disc.

Even after reading this it just seems too basic for me to have missed. I know I have a lot of lab work and studying still to do, but all that will mean nothing if I can't get my clients on the cloud at the end of the day.

Any help for this noob here? Sorry for the long post too...

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Comments

alan2308

The WIC-1B-U is ISDN, not Ethernet, so that's not going to work. Same jack basically, but not the same thing. You'll need an Ethernet interface on the router you want to connect to your home network.

Since your home network is most likely all private addresses, you'll need to set up port forwarding on your home router to forward port 23 to the Cisco router. I can't tell you how to do that without knowing what router it is, they're all different. Then you can telnet to your public IP address (assuming you're outside of your home network) and then you'll be getting into the Cisco. From inside your home network, just telnet to the IP address of the Ethernet port that's connected to your LAN.

stuh84

alan2308 wrote: »

The WIC-1B-U is ISDN, not Ethernet, so that's not going to work. Same jack basically, but not the same thing. You'll need an Ethernet interface on the router you want to connect to your home network.

Since your home network is most likely all private addresses, you'll need to set up port forwarding on your home router to forward port 25 to the Cisco router. I can't tell you how to do that without knowing what router it is, they're all different. Then you can telnet to your public IP address (assuming you're outside of your home network) and then you'll be getting into the Cisco. From inside your home network, just telnet to the IP address of the Ethernet port that's connected to your LAN.

Why would you want to forward mails to it?

j/k

For telnet, you'll want port 23, 22 if you have an IOS capable of SSH

alan2308

stuh84 wrote: »

Why would you want to forward mails to it?

j/k

For telnet, you'll want port 23, 22 if you have an IOS capable of SSH

DOH!

I just finished a class on penetration testing, I guess port 25 is just burned into my brain. I'll go fix that.

Abbeyandpapa

That already helps! Thank you! I will be using a 2620xm for it's built in fe-0/0 then.

As far as my Linksys, those are easy enough. It's already coming together in my head... ports, duh!

So forward TCP ports 22 and 23 for telnet and ssh, gotcha.

Here's my question though, how does NAT/PAT really work? Or is it even involved here since I'll just forward to the static ip of the 2620xm? And finally should I worry too much about NAT/PAT for CCNA?

alan2308

Abbeyandpapa wrote: »

That already helps! Thank you! I will be using a 2620xm for it's built in fe-0/0 then.

As far as my Linksys, those are easy enough. It's already coming together in my head... ports, duh!

So forward TCP ports 22 and 23 for telnet and ssh, gotcha.

Here's my question though, how does NAT/PAT really work? Or is it even involved here since I'll just forward to the static ip of the 2620xm? And finally should I worry too much about NAT/PAT for CCNA?

Yes, NAT is still involved since you the devices on your LAN (the Cisco 2620xm included) are using private addresses. So you have NAT and port forwarding going on when you access that device from outside your local LAN.

NAT/PAT is definitely a topic you need to know for CCNA. Its not that bad even though it can seem big and scary (like a lot of things) at first. Study and practice, you'll get it.

wastedtime

You may want to look at https://learningnetwork.cisco.com/docs/DOC-4975 which is the exam topics for the CCNA composite exam. It shows NAT as a major topic.

Abbeyandpapa

Hey thanks for the input, it makes all kinds of sense now. As far as NAT goes, I understand the basic function, but haven't had to configure it at the CLI yet (or SDM for that matter) so maybe when I get there it'll help clear up the fuzz some.

But all this has raised for me another question. There are a panoply of sites and posts about what router people like for different reasons, but there seems to be little in the way of breaking down NM's and WIC's and what is really needed. Are there any resources that you guys know of that break down modules?

The only interfaces I know I need are ethernet and serial (my NM-4 a/s is on its way) but beyond that it buy as I find out I need. The only one I know I don't need is token ring.

alan2308

You need Ethernet and serial ports, thats really it. And as far as which modules to get, it is heavily dependent on which routers that you have and which ports you think you need on those routers. With a NM-4as on its way, just make sure every router has an Ethernet port and at least one Serial port (though 2 is preferred). Beyond that all you need is the correct cables.

I've also read on Wendell Odom's blog that the T-1 modules are a lot cheaper. You can connect them together with a T1 crossover cable and its every bit as good as a serial port.