"The page cannot be found" when accessing valut from outside LAN

Hi,

I hope someone can help me..... If I enter http://servername/VaultService in 
my browser on a machine on my LAN I see the vault server homepage but if I 
try to see http://externalservername/VaultService then I get the "The page 
cannot be found" error. I can definately see other webapps on the same 
server using the external name.

Any ideas?

Thanks, Jerry

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