H3C Technologies H3C SecBlade NetStream Cards - Manual (Page 78)

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Displaying and maintaining an Ethernet interface or
subinterface
To do… Use the command… Remarks
Display Ethernet interface or
subinterface information
display interface [ interface-type ] brief [ down ] [ |
{ begin | exclude | include } regular-expression ]
display interface interface-type { interface-number
| interface-number.subnumber } [ brief ] [ | { begin
| exclude | include } regular-expression ]
Available in any view
Clear the interface or
subinterface statistics
reset counters interface [ interface-type
[ interface-number |
interface-number.subnumber ] ]
Available in user
view
Configuring a loopback interface
Because of the benefits mentioned above, loopback interfaces are widely used in the following
scenarios.
• You can configure a loopback interface address as the source address of the IP packets that the
device generates. Because loopback interface addresses are stable unicast addresses, they are
usually used as device identifications. Therefore, when you configure a rule on an authentication or
security server to permit or deny packets generated by a device, you can simplify the rule by
configuring it to permit or deny packets carrying the loopback interface address identifying the
device. Note that, when you use a loopback interface address as the source address of IP packets,
make sure that the route from the loopback interface to the peer is reachable by performing routing
configuration. All data packets sent to the loopback interface are considered as packets sent to the
device itself, so the device does not forward these packets.
• Because a loopback interface is always up, it can be used in dynamic routing protocols. For
example, if no router ID is configured for a dynamic routing protocol, the highest loopback interface
IP address is selected as the router ID.
Follow these steps to configure a loopback interface:
To do… Use the command… Remarks
Enter system view system-view —
Create a loopback interface and
enter loopback interface view interface loopback
interface-number
—
Set the interface description description text
Optional
By default, the description of a
loopback interface is interface name
Interface.
Shut down the loopback interface shutdown
Optional
By default, a loopback interface is up.