TFTP lockdown

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Feb 24th, 2009
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We have some security requirements to disable TFTP on certain routers and switches. What is the best (easiest) way to accomplish this? Looking at NO SERVICE CONFIG command, but not sure what all will result from this. Thanks for any suggestions

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Richard Burts Tue, 02/24/2009 - 05:01
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no service config is generally a good thing and is the default in IOS. Unless there is some reason why you want your router and switches to read their config from a TFTP server at boot time there is no negative impact of making sure that this service is not enabled.

Beyond that I am not aware of any realistic steps to disable TFTP. If someone enters the copy command with TFTP as one of its parameters then the router or switch will initiate TFTP to or from the indicated server. I am not aware of any way to prevent this.



Joseph W. Doherty Tue, 02/24/2009 - 05:59
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Can't think of a really easy way to accomplish, since as Rick notes, TFTP is a parameter on the copy command.

You might place ACLs to block TFTP ports. You might place TFTP command into a special privledge class and/or control via Tacacs+. You might be able to "short circuit" TFTP via EEM monitoring.

It's unclear the security risk you're trying to avoid. Routers and switches, by default, aren't, I believe, TFTP servers. Using TFTP on a router or switch would imply some type of administrative level control, so it would seem somewhat easier to just have an administrative policy precluding using TFTP. Otherwise, you're trying to control such administrative access. ACLs and perhaps EEMs might preclude accidental usage of TFTP, but only Tacacs+, with command authorization, or usage of different privledge levels, might be able to fully enforce this type of administrative access.

thlnm Tue, 02/24/2009 - 07:46
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Thanks - that makes a lot of sense and will help us going forward.


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