Routing Table structure
Fields: destination, gateway, flags, users, refcnt
Destination: can be a host address or a network address. Subnet mask also present, but implicit for this discussion. If the ‘H’ flag is set, it is the host address.
Gateway: router/next hop IP address. The ‘G’ flag says whether the destination is directly connected (link address & IP address refer to destination), or indirectly connected (link address refers to router’s, IP address refers to destination)
U flag: Is route up ? G: router (indirect vs direct)
H flag: host (dest field: host or n/w address?)
D & M flags: created/modified by ICMP redirect