| 6.3 | External Routers | ||
| 6.3.1 | Configuring external routers |
On an external router, an interface can
be logically divided into multiple, virtual subinterfaces.
Subinterfaces provide a flexible solution for routing multiple data
streams through a single physical interface. To accomplish this
goal, you need to customize the subinterface to create the
environment in which the subinterface is used. To define
subinterfaces on a physical interface, perform the following tasks:
To identify the interface, enter the following command in global configuration mode.
where slot-number/port-number.subinterface-number identifies the physical and logical interface. To define the VLAN encapsulation, enter the following command in interface configuration mode.
where vlan-number identifies the VLAN for which the subinterface will carry traffic. A VLAN ID is added to the frame only when the frame is destined for a nonlocal network. Each VLAN packet carries the VLAN ID within the packet header. To assign the IP address to the interface, enter the following command in interface configuration mode.
Where ip-address and subnet-mask are the 32-bit network address and mask of the specific interface. In the example, Route Processor has three subinterfaces configured on Fast Ethernet interface 0/0. These three interfaces are identified as 0/0.1, 0/0.10, and 0/0.20. All interfaces are encapsulated for ISL. Interface 0/0.1 is routing packets for VLAN 1, whereas interface 0/0.10 is routing packets for VLAN 10 and 0/0.20 is routing packets for VLAN 20.
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