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“hex data is limited to 100 characters” on Cisco ASA firewall

Matthew Evans

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While setting up some Polycom IP phones to use with Microsoft Lync 2010 for remote users, one of the requirements is that there are some very specific DHCP options that are set on the remote DHCP if this is the first time the phone is being configured.  There is a very useful web page here that can be used to setup remote Cisco devices with the required DHCP options 120 and 43.

Option 43 in DHCP requires a very long hex string to be created (ours is 188 hex characters long). When adding this option to the Cisco ASA firewall via the ASDM (GUI) interface I get the following error message:


hex data is limited to 100 characters

I thought I was going to be in trouble, but it appears that there is no such limitation when adding this command via the command line interface (CLI) on the firewall via Telnet or SSH.


dhcpd option 43 hex 010cXXXXXXXXXX interface inside

So while I prefer to do most things through the ASDM when possible this is another case when Cisco hasn’t reached parity between the graphical and command line interfaces.