H3C Technologies H3C SecBlade NetStream Cards - Manual (Page 70)

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Interface configuration
This chapter includes these sections:
• Ethernet interface overview
• General configuration
• Configuring a Layer 2 Ethernet interface or subinterface
• Configuring a Layer 3 Ethernet interface or subinterface
• Displaying and maintaining an Ethernet interface or subinterface
Ethernet interface overview
An interface is the point of interaction or communication between devices. It is used for exchanging data
between devices. A physical interface is an interface that materially exists and is supported by a device.
For example, an Ethernet interface is a physical interface. A logical interface is an interface that can
implement data switching but does not exist physically. A logical interface must be established through
configuration.
The device supports the following interfaces:
• Layer 2 Ethernet interfaces: They are physical interfaces operating on the data link layer for Layer
2 packet forwarding. They can only forward packets carrying source and destination IP addresses
that belong to the same network segment.
• Layer 3 Ethernet interfaces: They are physical interfaces operating on the network layer for Layer 3
packet forwarding, and forward packets carrying source and destination IP addresses that belong
to different network segments. You can assign an IP address to a Layer 3 Ethernet interface.
• Layer 2-Layer 3 Ethernet interfaces: They are physical interfaces that can operate on both the data
link layer and the network layer. When operating on the data link layer, a Layer 2-Layer 3 Ethernet
interface acts as a Layer 2 Ethernet interface. When operating on the network layer, a Layer 2-Layer
3 Ethernet interface acts as a Layer 3 Ethernet interface.
• Layer 2 Ethernet subinterfaces: They are logical interfaces operating on the data link layer. They are
mainly used for inter-VLAN packet forwarding on cards. By configuring Layer 2 Ethernet
subinterfaces for VLANs, you enable Layer 2 Ethernet packets to be forwarded across VLANs
through the corresponding Layer 2 Ethernet subinterfaces. The link type of a Layer 2 Ethernet
subinterface is access, which cannot be changed. Besides the Layer 2 subinterface configurations
described in this chapter, you can also assign a Layer 2 subinterface to a VLAN. For more
information, see the chapter ”VLAN configuration.”
• Layer 3 Ethernet subinterfaces: They are logical interfaces operating on the network layer. You can
assign an IP address to a Layer 3 Ethernet subinterface. By creating subinterfaces on a Layer 3
Ethernet interface, you can enable the interface to carry packets for multiple VLANs, which provides
great networking flexibility.
• Loopback interfaces: A software-only virtual interface. Once a loopback interface is created, its
physical status is always up and link layer protocols are enabled unless you manually shut down the
interface. You can enable routing protocols on a loopback interface, and enable it to receive and
transmit routing protocol packets. When you assign an IPv4 address for a loopback interface, the
subnet mask must be 32-bit long.