Configuring A Loopback0 Interface - Alcatel-Lucent OmniSwitch AOS Release 7 Manual

Configuring a Loopback0 Interface

Loopback0 is the name assigned to an IP interface to identify a consistent address for network manage-
ment purposes. The Loopback0 interface is not bound to any VLAN, so it always remains operationally
active. This differs from other IP interfaces in that if there are no active ports in the VLAN, all IP inter-
face associated with that VLAN are not active. In addition, the Loopback0 interface provides a unique IP
address for the switch that is easily identifiable to network management applications.
This type of interface is created in the same manner as all other IP interfaces, using the
command. To identify a Loopback0 interface, enter Loopback0 for the interface name. For example, the
following command creates the Loopback0 interface with an IP address of 10.11.4.1:
-> ip interface Loopback0 address 10.11.4.1
Note the following when configuring the Loopback0 interface:
•
The interface name, "Loopback0", is case sensitive.
•
The Loopback0 interface is always active and available.
•
Only one Loopback0 interface per switch is allowed.
•
Loopback0 address cannot be modified once it is configured.
•
Creating this interface does not deduct from the total number of IP interfaces allowed per VLAN or
switch.
•
To change the address the interface has to be removed using the no ip interface Loopback0 command
and re-add it with the new address.
Loopback0 Address Advertisement
The Loopback0 IP interface address is automatically advertised by the IGP protocols RIP and OSPF when
the interface is created. There is no additional configuration necessary to trigger advertisement with these
protocols.
Note the following regarding Loopback0 advertisement:
•
RIP advertises the host route to the Loopback0 IP interface as a redistributed (directhost) route.
•
OSPF advertises the host route to the Loopback0 IP interface in its Router-LSAs (as a Stub link) as an
internal route into all its configured areas.
Configuring a BGP Peer Session with Loopback0
It is possible to create BGP peers using the Loopback0 IP interface address of the peering router and bind-
ing the source (i.e., outgoing IP interface for the TCP connection) to its own configured Loopback0 inter-
face. The Loopback0 IP interface address can be used for both Internal and External BGP peer sessions.
For EBGP sessions, if the External peer router is multiple hops away, the ebgp-multihop parameter can
need to be used.
The following example command configures a BGP peering session using a Loopback0 IP interface
address:
-> ip bgp neighbor 2.2.2.2 update-source Loopback0
See the OmniSwitch AOS Release 7 Advanced Routing Configuration Guide for more information.
page 1110 OmniSwitch AOS Release 7 Network Configuration Guide
ip interface
March 2011