06-26-2022 01:01 AM
Just recently swapped out a C3200 with a C8500. The C3200 had an Aux port that we could use reverse telnet to access the modem which would dial another modem at a remote location and enter the router there as a backup connection (if the VPN to that remote location failed we could troubleshoot the cause.) The C8500 does not have a physical Aux port although the CLI shows one. I am trying to figure out how to accomplish the same goal by using the console port.
Here shows the "show line"
99Router(config)#do show line Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int * 0 CTY - - - - - 0 0 0/0 - 1 AUX 9600/9600 - - - - - 0 0 0/0 - * 2 VTY - - - - - 46 0 0/0 - 3 VTY - - - - - 7 0 0/0 - 4 VTY - - - - - 0 0 0/0 - 5 VTY - - - - - 0 0 0/0 - 6 VTY - - - - - 0 0 0/0 -
The cosole (Tty 0) is already in use by default so I cannot reverse telnet using x.x.x.x:2000
Any ideas how to use reverse telnet when you have no aux port? Or is there a physical aux port on the C8500 and I'm just totally blind?
06-26-2022 06:55 AM
I think since you have AUX you can config reverse telnet
1 AUX 9600/9600 - - - - - 0 0 0/0
please find below link for example how you can config
https://www.cisco.com/c/en/us/support/docs/dial-access/asynchronous-connections/5466-comm-server.html
06-26-2022 07:16 AM
I've looked at that page but it references "A terminal server is a router with multiple, low speed, asynchronous ports that are connected to other serial devices" but the 8500 has none of these (from what I can tell). The weird parts is the fact that the configuration shows an Aux port but there is not a physical aux port on the Catalyst 8500. Is there's a way to make an existing interface (serial or ethernet) emulate an Aux interface or can the 8500 just not do reverse telnet?
06-26-2022 05:43 PM
I do not have experience with this model. But my guess is that the config shows line aux 0 because it is part of the standard template for parsing the configuration.
If there is no physical port then there is no way to physically connect to the modem. I think you will need to find a different way to connect to the other site.
06-26-2022 06:11 PM
I see numerous examples of things like this in configs. For example I see this in many config
multilink bundle-name authenticated
when there is absolutely no multilink capability in the router.
06-06-2024 10:53 PM
I am afraid this feature is unfortunately gone. I had same trail of thoughts and was wondering if we can use mgmt/con port as aux with certain setup but never found anything. Router replacements were sooo much easier with reverse telnet.
06-07-2024 12:19 PM
Hello,
as far as I recall, the console port on the 8500 is an EIA/TIA-232 asynchronous, serial connection with no flow control and an RJ-45 connector. Hence, in theory, you could use it the same way as the AUX port on older devices. Can you try to use the console port ? Not sure it works, I have not tested it...
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide