This filter protocol object matches the Internet
Protocol Number in the packets. These IP numbers
are defined in the Network Working Group Request
for Comments (RFC) documents. For example,
Cisco commonly used protocol includes:
1 - Internet Control Message Protocol
2 - Internet Gateway Message Protocol
4 - IP in IP tunneling
6 - Transmission Control Protocol
9 - Cisco's IGRP routing protocol
17 - User Datagram Protocol
47 - Cisco's GRE tunneling
50 - Encapsulation Security Payload
51 - Authentication Header Protocol
88 - Cisco's EIGRP routing protocol
89 - OSPF routing protocol
94 - KA9Q NOS compatible IP over IP tunneling
103 - Protocol Independent Multicast
108 - Payload Compression Protocol
Setting this object to '-1' will make the
filtering match any IP number.