Wendell odom

17
Chapter 17: IP Routing in the LAN 399
Example 17-3
 Connected 
Routes 
Based on Example 17-1 Configuration
B1# 
show ip route connected
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
! Legend omitted for brevity
10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C 10.1.10.0/24 is directly connected, GigabitEthernet0/0.10
L 10.1.10.1/32 is directly connected, GigabitEthernet0/0.10
C 10.1.20.0/24 is directly connected, GigabitEthernet0/0.20
L 10.1.20.1/32 is directly connected, GigabitEthernet0/0.20
As for interface and subinterface state, note that the ROAS subinterface state does depend 
to some degree on the physical interface state. In particular, the subinterface state cannot 
be better than the state of the matching physical interface. For instance, on Router B1 in the 
examples so far, physical interface G0/0 is in an up/up state, and the subinterfaces are in an 
up/up state. But if you unplugged the cable from that port, the physical port would fail to a 
down/down state, and the subinterfaces would also fail to a down/down state. Example 17-4 
shows another example, with the physical interface being shut down, with the subinterfaces 
then automatically changed to an administratively down state as a result.
Example 17-4
Subinterface State Tied to Physical Interface State
B1# 
configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
B1(config)# 
interface g0/0
B1(config-if)# 
shutdown
B1(config-if)# 
^Z
B1# 
show ip interface brief | include 0/0
GigabitEthernet0/0 unassigned YES manual administratively down down
GigabitEthernet0/0.10 10.1.10.1 YES manual administratively down down
GigabitEthernet0/0.20 10.1.20.1 YES manual administratively down down
Additionally, the subinterface state can also be enabled and disabled independently from the 
physical interface, using the