Configuring A Loopback Interface; Displaying Loopback Interface Configuration - Cisco Catalyst 8540 MSR Configuration Manual
Atm switch router software configuration guide
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Chapter 16
Configuring Tag Switching and MPLS
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Configuring a Loopback Interface
You should configure a loopback interface on every ATM switch router configured for tag switching. The
loopback interface, a virtual interface, is always active. The IP address of the loopback interface is used
as the Tag Distribution Protocol (TDP) identifier for the ATM switch router. If a loopback interface does
not exist, the TDP identifier is the highest IP address configured on the ATM switch router. If that IP
address is administratively shut down, all TDP sessions through the ATM switch router restart.
Therefore, we recommend that you configure a loopback interface.
To configure the loopback interface, perform the following steps, beginning in global configuration
mode:
Command
Step 1
Switch(config)# interface loopback number
Switch(config-if)#
Step 2
Switch(config-if)# ip address ip-address mask
1.
Example
In the following example, loopback interface 0 is created with an IP address of 1.0.1.11 and a subnet
mask of 255.255.255.255:
Switch(config)# interface loopback 0
Switch(config-if)# ip address 1.0.1.11 255.255.255.255
Switch(config-if)# exit
Displaying Loopback Interface Configuration
The following example shows the loopback 0 configuration using the show interfaces privileged EXEC
command:
Switch# show interfaces loopback 0
Loopback0 is up, line protocol is up
Hardware is Loopback
OL-7396-01
Configuring a VPI Range (Optional), page 16-6
Configuring TDP Control Channels (Optional), page 16-8
Configuring Tag Switching on VP Tunnels, page 16-9
Connecting the VP Tunnels, page 16-11
Configuring VC Merge, page 16-12
TVCs = tag virtual channels.
Purpose
Enters interface configuration mode and assigns a
number to the loopback interface.
Assigns an IP address and subnet mask to the
loopback interface.
We recommend a 32-bit subnet mask
Note
(255.255.255.255) for the loopback
interface. If you do not use a 32-bit subnet
1
mask, two TVCs
address—one for a 32-bit subnet mask
and the other for the mask you entered.
Entering a 32-bit subnet mask reduces the
number of TVCs to one.
ATM Switch Router Software Configuration Guide
Configuring Tag Switching
terminate for the same
16-3
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