apache - url only available by IP address after rewriteRule -

i not familiar apache rewrite. tried add line following 1 of our virtual hosts config in apache

rewriterule /favicon.ico http://example.com/favicon.ico [r=301,l] 

then try access using:

http://myexample.com/favicon.ico

i got 404. however, if use:

http://theip/favicon.ico

i got right redirect. totally confused.

would appreciate if can share hints/thoughts. thank you