Cisco Systems 1000 Series Manual De Usuario

Telnet and Secure Shell (SSH) on the Cisco ASR 1000 Series Routers can be configured and handled 
like Telnet and SSH on other Cisco platforms. For information on traditional Telnet, see the line

 

command in the Cisco IOS Terminal Services Command Reference guide located at: 

http://www.cisco.com/en/US/docs/ios/12_2/termserv/command/reference/trflosho.html#wp1029818. 

For information on configuring traditional SSH, see the “Configuring Secure Shell” chapter of the Cisco 
IOS Security Configuration Guide located at: 

The Cisco ASR 1000 Series Routers also introduces persistent Telnet and persistent SSH. Persistent 
Telnet and persistent SSH allow network administrators to more clearly define the treatment of incoming 
traffic when users access the router through the Management Ethernet port using Telnet or SSH. Notably, 
persistent Telnet and persistent SSH provide more robust network access by allowing the router to be 
configured to be accessible through the Ethernet Management port using Telnet or SSH even when the 
IOS process has failed.

In traditional Cisco routers, accessing the router using Telnet or SSH is not possible in the event of an 
IOS failure. When Cisco IOS fails on a traditional Cisco router, the only method of accessing the router 
is through the console port. Similarly, if all active IOS processes have failed on a Cisco ASR 1000 Series 
Router that is not using persistent Telnet or persistent SSH, the only method of accessing the router is 
through the console port.

With persistent Telnet and persistent SSH, however, users can configure a transport map that defines the 
treatment of incoming Telnet or SSH traffic on the Management Ethernet interface. Among the many 
configuration options, a transport map can be configured to direct all traffic to the IOS command-line 
interface, diagnostic mode, or to wait for an IOS vty line to become available and then direct users into 
diagnostic mode when the user sends a break signal while waiting for the IOS vty line to become 
available. If a user uses Telnet or SSH to access diagnostic mode, that Telnet or SSH connection will be 
usable even in scenarios when no IOS process is active. Therefore, persistent Telnet and persistent SSH 
introduce the ability to access the router via diagnostic mode when the IOS process is not active. For 
information on diagnostic mode, see the 

See the 

 and the 

 for information on the various other options that are configurable using persistent 

Telnet or persistent SSH transport maps.