Console vs. Auxiliary

Whether the console and aux ports are RJ45 ports or not depends on the platform. The newer platforms tend to be RJ45 ports.

You will mostly use the console port to manage the box by reverse telnetting to it. The aux port tends to come into use when you need remote access to the box via a modem. Only the aux port can support a modem connected to it that you can dial into.

Cisco da Gama

In article , " snipped-for-privacy@gmail.com" writes

What do you mean by "reverse telnet" ? Is this a routine telnet session, e.g.:

telnet 1.2.3.4 23

What is the console port physically cabled to?

You can connect a flat, green cable between the console port on your router and an access port on an access server like the AS-2511RJ. This is called a "rolled cable" on exams or a "console cable" in real life.

Suppose you connect your console port to port 5 on the access server, and the access server has ip address 128.0.0.1. You then would use the command, "telnet 128.0.0.1 2005" to access your router. If you connect to port 12 on the access server, you would use the command "telnet

128.0.0.1 2012" to access your router. This is called reverse telnet.

You can do the same thing with the auxiliary port, except you need a flat, pale-blue cable. You can call this an "aux cable" if you like.

Serial connectors... complicate things. I encourage you to check out this page because it will help on the exam and in the real world:

Basic cabl>In article ,

That may be one use, but I wouldn't say that is the usual use. Generally the console cable is what you'll use to physically connect your notebook to configure the system or reload. AUX port is also used in conjunction with a modem for remote sites. You can use those two ports for reverse telnet and many other access needs.

The only real difference is the AUX port uses hardware flow control, where the CON port has no flow control.

I wouldn't get attached to those colours, nor the "flatness" of the cable - this is solely for local identification.

I needed a console cable in a hurry once so made one up from what I had to hand - white Cat5 UTP.

Aubrey

Conventions minimize errors and simplify debugging. I wanted to help the original poster visualize how things should really look.

That's a good point. In an emergency, mix cables, adaptors, and extenders as necessary... but re-standardize as soon as possible.

The link I sent earlier explains how to mix those parts.

In article , hb350001 writes

Would you typically leave the console port connected to an access port on an access server as a permanent installation? Is it the console port on a switch or router which has the device's own IP configured rather than any other interface?

If you don't connect the console port to an access server, can you still telnet to the router/switch via the production network?

Depending on how many routers you have in your network, leaving the console port connected to a comm-server may not be practical. With a few routers is certainly reasonable to have all their console ports connected to a comm-server for easy manageability.

configured > rather than any other interface?

You seem to be misunderstanding something here. The console port does not have an IP address. The console port is reached via the IP address of the comm-server using reverse-telnet explained earlier in this thread.

Sure you can. You just need to make sure that routing is set up fine so that you can telnet to the router over one of its network interfaces.

Cisco da Gama

In article , " snipped-for-privacy@gmail.com" writes

I see. So, in a large infrastructure why would you bother to use an access server at all? Why not just telnet direct to each router/switch?

Ah, understood, thanks.

It depends. An access server costs $1500 anconnects upto 16 devices. Ask yourself how important is 24/7 remote access to a device?

For wireless access points and desktop switches, an after-hours outage can probably wait until the next business day for debugging. However, a core switch, router, or server outage may require an immediate fix.

A permanent access server means you can debug these problems faster and usually without spending time travelling to/from the office.

• Telnet is not an option when you initially configure a device. You have to use the console port

• Telnet is not an option for some troubleshooting scenarios--such as recovering a password.

• In many network designs, the management network is more reliable than the production traffic network.

• Having full remote access limits how much time you spend walking between devices vs. troubleshooting them

• When 24/7 uptime of a device is important, 24/7 full remote access to those same devices is also important.

In article , hb350001 writes

That's wonderful -- many thanks for your time answering my questions.

someone in here posted that you can't connect a modem to a console port. yes you can. I've connected to many a router like this. the modem will answer your call, not the router in this case. use hyperterminal to do it. it's been about 5years since i've done it though, but it CAN be done.

That was me saying earlier that the AUX port is usually used to connect modems to. I didn't mean to imply that modems could not be connected to console ports. Note that though possible, there are several potential issues to be aware of while connecting modems to console ports. Please take a look at

Cisco da Gama

I concur on this point and one huge reason why you would connect a modem to the console port instead of the aux port is that if you reload the router the aux port will reset and the modem will drop whereas the console port stays connected and you can use that to access rommon or watch the boot process.