Wendell odom

ip address
command on the physical interface, but without an 
encapsulation
command; the router considers this physical interface to be using the 
native VLAN.
■
Configure the 
ip address
command on a subinterface and use the 
encapsulation dot1q 
vlan-id
 native
subcommand to tell the router both the VLAN ID and the fact that it is the 
native VLAN.
Example 17-2 shows both native VLAN configuration options with a small change to the 
same configuration in Example 17-1. In this case, VLAN 10 becomes the native VLAN. The 
top part of the example shows the option to configure the router physical interface to use 
native VLAN 10. The second half of the example shows how to configure that same native 
VLAN on a subinterface. In both cases, the switch configuration also needs to be changed 
to make VLAN 10 the native VLAN.
Example 17-2
Router Configuration Using Native VLAN 10 on Router B1
! First option: put the native VLAN IP address on the physical interface
interface gigabitethernet 0/0
ip address 10.1.10.1 255.255.255.0
!
interface gigabitethernet 0/0.20
encapsulation dot1q 20
ip address 10.1.20.1 255.255.255.0
! Second option: like Example 17-1, but add the 
native
keyword
interface gigabitethernet 0/0.10
encapsulation dot1q 10 native
ip address 10.1.10.1 255.255.255.0
!
interface gigabitethernet 0/0.20
encapsulation dot1q 20
ip address 10.1.20.1 255.255.255.0 
Verifying ROAS
Beyond using the 
show running-config
command, ROAS configuration on a router can be 
best verified with two commands: 
show ip route
[
connected
] and 
show vlans
. As with any 
router interface, as long as the interface is in an up/up state and has an IPv4 address con-
figured, IOS will put a connected (and local) route in the IPv4 routing table. So, a first and 
obvious check would be to see if all the expected connected routes exist. Example 17-3 lists 
the connected routes per the configuration shown in Example 17-1.
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7/25/19 2:45 PM

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