10.10 Changing the State
of the Token-Ring Network Interface
10.10 Changing the State
of the Token-Ring Network Interface
Any packets sent to destinations not previously defined and not on a directly- connected network will go through the default gateway. Without the default gateway defined in the routing table, remote destinations are unreachable.
Consider a remote host with IP address 9.8.0.8. The traceroute command output shows the path used to get there starting from the default gateway:
# netstat -rn Routing tables Destination Gateway Flags Refs Use If PMTU Exp Groups Route Tree for Protocol Family 2 (Internet): default 9.3.1.74 UG 0 0 tr0 - - 9.3.1/24 9.3.1.141 U 12 1501 tr0 - - 127/8 127.0.0.1 U 2 382 lo0 - - 192.168.0/16 192.168.3.1 U 0 4 en0 - - Route Tree for Protocol Family 24 (Internet v6): ::1 ::1 UH 0 0 lo0 16896 - # ping 9.8.0.8 PING 9.8.0.8: (9.8.0.8): 56 data bytes 64 bytes from 9.8.0.8: icmp_seq=0 ttl=49 time=384 ms 64 bytes from 9.8.0.8: icmp_seq=1 ttl=50 time=354 ms ^C ----9.8.0.8 PING Statistics---- 2 packets transmitted, 2 packets received, 0% packet loss round-trip min/avg/max = 354/369/384 ms # traceroute 9.8.0.8 trying to get source for 9.8.0.8 source should be 9.3.1.141 traceroute to 9.8.0.8 (9.8.0.8) from 9.3.1.141 (9.3.1.141), 30 hops max outgoing MTU = 1492 1 itso.austin.ibm.com (9.3.1.74) 11 ms 2 ms 2 ms 2 9.444.33.129 (9.444.33.129) 4 ms 4 ms 4 ms 3 9.444.33.129 (9.444.33.129) 4 ms 4 ms 4 ms 4 site1.austin.ibm.com (9.3.90.200) 7 ms site2.south.ibm.com (9.3.200.20 2) 8 ms 7 ms 5 site3.austin.ibm.com (199.4.213.125) 17 ms 19 ms 17 ms 6 9.88.1.174 (9.88.1.174) 74 ms 80 ms 71 ms 7 9.8.0.8 (9.8.0.8) 327 ms 329 ms 327 ms #
Without the default gateway, only the directly attached hosts are accessible and the remote destination can no longer be reached:
# route -f default itsorusi.itsc.austin done # netstat -rn Routing tables Destination Gateway Flags Refs Use If PMTU Exp Groups Route Tree for Protocol Family 2 (Internet): 9.3.1/24 9.3.1.141 U 11 1265 tr0 - - 127/8 127.0.0.1 U 2 382 lo0 - - 192.168.0/16 192.168.3.1 U 0 4 en0 - - Route Tree for Protocol Family 24 (Internet v6): ::1 ::1 UH 0 0 lo0 16896 - # ping 9.8.0.8 PING 9.8.0.8: (9.8.0.8): 56 data bytes 0821-069 ping: sendto: Cannot reach the destination network. ping: wrote 9.8.0.8 64 chars, ret=-1 0821-069 ping: sendto: Cannot reach the destination network. ping: wrote 9.8.0.8 64 chars, ret=-1 ^C ----9.8.0.8 PING Statistics---- 2 packets transmitted, 0 packets received, 100% packet loss # traceroute 9.8.0.8 trying to get source for 9.8.0.8 source should be 9.3.1.141 traceroute to 9.8.0.8 (9.8.0.8) from 9.3.1.141 (9.3.1.141), 30 hops max sendto: Cannot reach the destination network. 1 traceroute: Partial write of -1 bytes outgoing MTU = 32768 *sendto: Cannot reach the destination network. traceroute: Partial write of -1 bytes *sendto: Cannot reach the destination network. traceroute: Partial write of -1 bytes ^C# # ping 9.3.1.124 PING 9.3.1.124: (9.3.1.124): 56 data bytes 64 bytes from 9.3.1.124: icmp_seq=0 ttl=255 time=0 ms 64 bytes from 9.3.1.124: icmp_seq=1 ttl=255 time=0 ms ^C ----9.3.1.124 PING Statistics---- 2 packets transmitted, 2 packets received, 0% packet loss round-trip min/avg/max = 0/0/0 ms #
10.12 Problem With
Incorrect Subnet Mask