Ethernet Switches & Routers

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New Contributor
andy.swanson
Posts: 4
Registered: ‎04-29-2011

Cisco 3600 terminal Server Connection to MLX console port

I am trying to create a console connection from a Cisco 3600 with async modules to an MLX console port. CIsco async modules have a 68 pin octal cable that converts into multiple rj45 cables  (8) and goes into a patch panel. The only way I could make this work with a Brocade device is to use a null modem with rj45 to db9 adapter..... This is what I would expect for DTE to DTE.

However, cisco console ports are also DTE and in the octal cable docs it states the (octal rj45 cables) cables are rolled, hence making it possible to connect directly to other cisco console (rj45) port that are DTE (no null modem). So if Brocade DB9 console ports are also DTE , as I have read they are, it should work without a null modem?? I have also read that Brocade has to see DTE at the other end which would make sense as to why I need a null modem in this case. (This was from a non-brocade source though and I would like this verifed from a brocade source before buying that as a fact)

**** Below is the excerpt that I am pasting from cisco documentation on the octal cable

Cabling

The Cisco 2509 - 2512 series routers (applies to 3600 as well)  use a 68-pin connector and breakout cable. This cable (CAB-OCTAL-ASYNC)  provides eight RJ-45 rolled cable async ports on each 68-pin connector.  You can connect each RJ-45 rolled cable async port to the console port  of a device. The 2511 router allows for a maximum of 16 devices to be  remotely accessible. In addition, the NM-16A or NM-32A high density async network modules are available for the Cisco 2600 and  3600 series routers to provide the same function. For more information  on cabling refer to the Let's Connect:Your Serial Cable Guide and the Cabling Guide for Console and AUX Ports.

Note: The async ports from the 68-pin connector are data  terminal equipment (DTE) devices. DTE to DTE devices require a rolled  (null modem) cable and DTE to data circuit-terminating equipment (DCE)  devices require a straight-through cable. The CAB-OCTAL-ASYNC cable is  rolled. Therefore, you can connect each cable directly to the console  ports of devices with RJ-45 interfaces. However, if the console port of  the device to which you connect is a 25-pin interface (DCE), you must  use the RJ-45 to 25-pin adapter marked "Modem" (to reverse the "roll")  in order to complete the connection.

This table shows the port types for console and auxiliary ports on Cisco routers and switches:

Interface Type DB25 Interface RJ-45 Interface
ConsoleDCEDTE
AUXDTEDTE

Can anyone tell me if I have to use null modem or there is something else that I am missing.

Thanks

Andy

New Contributor
andy.swanson
Posts: 4
Registered: ‎04-29-2011

Re: Cisco 3600 terminal Server Connection to MLX console port

The answer is yes you do need a null modem with this setup. I swapped the TX/RX pins (2/3) on the rj45 to DB9 adapter and everything works fine. The reason this is required is that the cisco octal cable is rolled. ( so that it can connect to another cisco console port DTE with no issues)

Frequent Contributor
ybzahr
Posts: 94
Registered: ‎07-02-2012

Re: Cisco 3600 terminal Server Connection to MLX console port

Hello Community,

Even if this thread is a bit old, a quick follow-up.

I have found myself in the same situation with 2651XM console routers from Cisco that I use for Out-of-Band management towards multiple devices (MLXe, CER-RT, FCX, etc.).

As said before, because Cisco swaps pins in they octal cables, I used Cisco classic rollover console cables (little blue ones) with the router and all worked just fine.

HTH.

Y.

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