A few days ago, a reader sent me an e-mail titled “Telnet Automation from a Cisco Router” and complained that IOS Tcl does not support the expect commands (spawn, send and expect). Since Expect is a Tcl extension, not part of the core Tcl, it’s not included in Cisco IOS, which was the only answer I could give.

However, it turned out that the reader actually wanted to trigger HTTP requests from the router. Cisco IOS Tcl has some built-in client-side HTTP support, but it’s far simpler to rely on the built-in http: file system. For example, to do a HTTP GET request, use the following Tcl command:

rtr#tclsh
rtr(tcl)#set result [exec {more http://webServer/index.html}]
<h1>Empty</h1>

As always, there are a few caveats:

• You can trigger HTTP GET requests, but not the PUT or POST requests.
• The server-side script should always return the HTTP status 200 (successful), otherwise the more command will fail. The actual status can be passed in the HTML response.

You can use the same trick to trigger HTTPS requests from Tcl.