Introduction

This article explains a caveat while operating an IOS XR XR7 router (Cisco 8000 / NCS-540L platform) through the physical console port.

Problem Description

It is possible that the XR7 console access seems to be stuck or hung up according to user's keystroke when operating an IOS XR XR7 router through the physical console port.

Once an IOS XR XR7 router gets in this state, the following symptoms can be seen:

• No output character will be shown up on the XR console output.
• No input character will be echoed back on the XR console output.
• User can still login to an IOS XR XR7 router via SSH/Telnet to manage an IOS XR XR7 router with no problem.
• BMC console is available and user can access to XR (x86) from the BMC console. (BMC is applicable to some Cisco 8000 platforms only)

Solution

Flow control functionality is enabed on the XR7 console by default, and the below keystroke can stop or resume the XR7 console output.

• "Ctrl+s" (Stop): Press "s" while holding on "Control" key ("s" of "software")
• "Ctrl+q" (Start): Press "q" while holding on "Control" key ("q" of "question")

When user presses "Ctrl+s" (Stop) on the XR console, it will enable flow control and no output will be seen on the XR console until resumed.

When user presses "Ctrl+q" (Start) on the XR console, it will resume the XR console output again.