Set the Telnet Source IP Address for a Cisco Router

Posted June 18, 2006 by Quinn McHenry in Cisco router

The default source IP address when telnetting from a Cisco router is that of the interface closest to the destination. Because some access lists may block traffic from the default IP address, it may be useful to temporarily or permanently set the telnet source IP address. This also helps test access lists.

To temporarily set the telnet source IP address for a single telnet session, use the /source-interface extension to the telnet command.

For example, to telnet to using the source IP address of the interface FastEthernet0:

telnet /source-interface FastEthernet0

To set this interface as the source IP address for all telnet sesions, use this command in configuration mode (conf t):

ip source-interface fastethernet0


About Quinn McHenry

Quinn was one of the original co-founders of Tech-Recipes. He is currently crafting iOS applications as a senior developer at Small Planet Digital in Brooklyn, New York.
View more articles by Quinn McHenry

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  • Brilliant tip, got me out of a hole tonight!

  • Mike

    Anything similar for SSH?

  • Richey

    This command did not work on a box with 12.3. I used “ip telnet source-interface interface fa0/0”

  • Satyadevan W

    how to assign an ipaddress for auxiliary port in a router

  • mike

    Thx dude

  • Greek

    How to use specific ip address, if interface has many secondary ip addresses?

    I have not any idea 🙁