Sunday, 17 February 2013

Applying Cisco's New Licenses Without Network Servers

Cisco have a new licensing method that involves installing an XML license on the end device. The license you buy is a code but rather than just entering that onto the device you have to go to Cisco.com and associate the code with a device using part and serial number. Then they generate an XML license file which you are supposed to download and install on the device.

The ways they support doing this are FTP, SCP, TFTP, HTTP, which is no use if you're in a locked down environment, especially working remotely. Luckily as most of their boxes now include TCL so you can fudge it to paste the license straight on via a terminal. Thanks muchly to http://www.internetworkpro.org/wiki/Edit_files_using_TCL The license looks something like this:
<?xml header stuff?>
<SomeStuff></SomeStuff>
<SomeMoreStuff></SomeMoreStuff>
<license><![CDATA[loadsandloadsofrandomgarbagethatisfartoolongtofitonasinglelineofxmlsoyouneedtosplitthislineupintoseveraldifferentvariablesthisfieldcontainsabinaryloadofgunkpretendingitsopenandinteroperablebecauseitsxml]]></license>
<EvenMoreStuff></EvenMoreStuff>

The trick is to use TCL. You create a TCL variable containing the license file data and write it to a text file on the flash memory. The problem is that the license file contains a blob in a CNAME field that is longer than the maximum TCLSH line length. One way around this is to break the file down into multiple lines, store each as a separate variable and write the lot into the same file without any line returns in between.

Several things to watch out for:
  • Don't put extra carriage returns in as the license will not be valid
  • Don't paste carriage returns as it seems to mess up the TCL shell - paste one line at a time then hit enter
  • The +> prompt means TCL is still accepting input for the same variable.
The commands are:
Router#tclsh
Router(tcl)#set file [open "flash:keyfile.lic" w+]

Router(tcl)#set line1 {
+><?xml header stuff?>
+><SomeStuff></SomeStuff>
+><SomeMoreStuff></SomeMoreStuff>
+><license><![CDATA[loadsandloadsofrandomgarbagethatisfartoolongtofitonasinglelineofxml}
Router(tcl)#set line2 {<soyouneedtosplitthislineupintoseveraldifferentvariablesthisfieldcontainsabinary>}
Router(tcl)#set line3 {<loadofgunkpretendingitsopenandinteroperablebecauseitsxml]]></license>
<EvenMoreStuff></EvenMoreStuff>}


Router(tcl)#puts -nonewline $file $line1
Router(tcl)#puts -nonewline $file $line2
Router(tcl)#puts -nonewline $file $line3
Router(tcl)#close $file

Router(tcl)#tclquit
Router#license install flash:keyfile.lic


Now you have the license in place, so all is great! Except that you need to reboot it to activate, hope you weren't running any live services on this box!

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