Redundant TFTP servers

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Sep 6th, 2007
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Hi everyone,

I'm currently trying to develop a scenario for implementation of redundant TFTP servers with a single public IP address. I was thinking for doing NAT statements with route-maps and SLA monitoring but I found out that there's no way to verify the availability of a TFTP service with the tools offered by SLA monitoring. So I remembered about TCL and thought about the following scenario: to issue copy tftp null: every X seconds and if the result is successful to preserve the original NAT statement. If it's not then verify the second TFTP server with the same command and if successful to remove the original NAT statement and put the new one. May become a little bit more complex at the moment the primary server goes down and I want to use it always as primary but that's not an issue. I'm not familiar with TCL but I took a look at some scripts and decided it's possible. Now the only question left - is it possible to run a TCL script regularly (like a cron)? If not than I'll have to do this on a Linux machine doing the same tests and logging in to the device in order to manipulate the NAT statements. Honestly said I prefer the first way and if possible I'm going for it. Of course, if anyone is familiar with an IOS tool capable of successfully monitoring a TFTP service the result of which can be used in a route-map, I'll be glad if it's shared:) Thanks in advance!

Best Regards,

Stefan Stefanov

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Joe Clarke Thu, 09/06/2007 - 10:04
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Provided your IOS is new enough, it is possible to run a TCL script in kron. However, the Embedded Event Manager is probably more along the lines of what you want. With EEM, you can create a TCL cron timer policy that executes the scenario above.

You can get more info on writing EEM TCL policies from . If you have specific questions on implementation, just follow up on this thread.

thegrave2000 Thu, 09/13/2007 - 11:13
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Thanks for the information Joe, hadn't noticed that EEM can do such things though I have some memories going through the IOS config guide for it. If this goes to an implementation phase and I have problems (and I surely will have such with my poor coding skills) I'll come back. Take care!


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