noise on console port

liamkennedy · ‎01-24-2007

I noticed a number of failed console port logins in our tacacs logs from a couple of remote routers. In both cases the usernames are gibberish - random characters in one case; access-list logs in the other.

logging in to these 2 routers (both 870s)I can see a lot of noise on the console ports. Anyone know what could be causing this?

router#sh line

Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int

0 CTY - - - - - 0 46524396 374144/0 -

1 AUX 0/0 - - - - - 0 0 0/0 -

* 2 VTY - - - - 61 5 0 0/0 -

3 VTY - - - - 61 0 0 0/0 -

4 VTY - - - - 61 0 0 0/0 -

5 VTY - - - - 61 0 0 0/0 -

6 VTY - - - - 61 0 0 0/0 -

sample log:

pciaccio · ‎01-24-2007

Check and reverify your settings for the Async Console port. It should be 9.6k 8 data bits, 1 stop bit and no parity. You may have a mismatch somewhere, possibly the DTE equipment or even the setup on the router. Do a show line cty 0 and see how it is set up...

liamkennedy · ‎01-24-2007

well there shouldn't actually be anything plugged into the console, though I have no way of checking this.

#sh line con 0

Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int

0 CTY - - - - - 0 46983615 374144/0 -

Line 0, Location: "", Type: ""

Length: 24 lines, Width: 80 columns

Baud rate (TX/RX) is 9600/9600, no parity, 1 stopbits, 8 databits

Status: Ready

Capabilities: none

Modem state: Ready

Special Chars: Escape Hold Stop Start Disconnect Activation

^^x none - - none

Timeouts: Idle EXEC Idle Session Modem Answer Session Dispatch

02:00:00 never none not set

Idle Session Disconnect Warning

never

Login-sequence User Response

00:00:30

Autoselect Initial Wait

not set

Modem type is unknown.

Session limit is not set.

Time since activation: never

Editing is enabled.

History is enabled, history size is 20.

DNS resolution in show commands is enabled

Full user help is disabled

Allowed input transports are none.

Allowed output transports are telnet.

Preferred transport is none.

No output characters are padded

No special data dispatching characters

looks ok to me.

pciaccio · ‎01-24-2007

Looks OK to me as well... Check to see if anything is actually plugged into it. You may have an open cable hanging off the port that is causing an antenna effect and causing impulse hits on the line. You may have bad cabling (A bad RJ-45 head or adaptor) or possibly the console port is defective...