Why isn't 'ether proto \ip host host' a legal tcpdump expression?

view story

http://serverfault.com – In its description of valid tcpdump expressions, the pcap-filter man pages state: The filter expression consists of one or more primitives. Primitives usually consist of an id (name or number) preceded by one or more qualifiers. In turn, these qualifiers are type, dir and proto. So far so good, but further down we find this: ip host host which is equivalent to: ether proto \ip and host host In the first case, ip and host are, respectively, proto and type. What pattern does ether proto \ip follow? Isn't that, as a whole, a proto qualifier? If so, why isn't (a properly escape (HowTos)