netstat -r
Another option relevant to performance is the display of the discovered Path Maximum Transmission Unit (PMTU). Use the netstat -r command to display this value.
For two hosts communicating across a path of multiple networks, a transmitted packet will become fragmented if its size is greater than the smallest MTU of any network in the path. Because packet fragmentation can result in reduced network performance, it is desirable to avoid fragmentation by transmitting packets with a size no larger than the smallest MTU in the network path. This size is called the path MTU.
The following is an example of the netstat -r
-f inet command used to display only the routing tables:
# netstat -r -f inet
Routing tables
Destination Gateway Flags Refs Use If PMTU Exp Groups
Route tree for Protocol Family 2 (Internet):
default res101141 UGc 0 0 en1 - -
ausdns01.srv.ibm res101141 UGHW 1 4 en1 1500 -
10.1.14.0 server1 UHSb 0 0 en1 - - =>
10.1.14/24 server1 U 3 112 en1 - -
brown17 loopback UGHS 6 110 lo0 - -
10.1.14.255 server1 UHSb 0 0 en1 - -
magenta res1031041 UGHW 1 42 en1 - -
127/8 loopback U 6 16633 lo0 - -
192.1.6.0 en6host1 UHSb 0 0 en0 - - =>
192.1.6/24 en6host1 U 0 17 en0 - -
en6host1 loopback UGHS 0 16600 lo0 - -
192.1.6.255 en6host1 UHSb 0 0 en0 - -
192.6.0.0 fc0host1 UHSb 0 0 fc0 - - =>
192.6.0/24 fc0host1 U 0 20 fc0 - -
fc0host1 loopback UGHS 0 0 lo0 - -
192.6.0.255 fc0host1 UHSb 0 0 fc0 - -