Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 787)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 763
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Configuring BGP-based auto-discovery for VPLS
8
About loopback interfaces and the router ID
In most configurations, a Brocade device has multiple IP addresses, usually configured on different
interfaces. As a result, a Brocade device’s identity to other devices varies depending on the
interface to which the other device is attached. BGP4 identifies a Brocade device by just one of the
IP addresses configured on the device, regardless of the interfaces that connect the devices. This
IP address is the router ID also known as the Label Switched Router (LSR) ID.
LDP uses the default loopback address as the router ID. Since VPLS auto-discovery uses the
services of LDP, a valid loopback address must be configured on the Brocade device before VPLS
auto-discovery can be enabled. When a loopback address is not configured, the LDP router ID is
NULL and VPLS auto-discovery does not function.
When there are several loopback addresses configured on the device, the default loopback
address is the IP address configured on the lowest-numbered loopback interface on the Brocade
device. For example, when the user configures loopback interfaces 1, 2, and 3 as follows, the
default router ID is 10.9.9.9/24.
Loopback interface 1, 10.9.9.9/24
Loopback interface 2, 10.4.4.4/24
Loopback interface 3, 10.1.1.1/24
Changes that occur when a loopback interface is deleted
When a loopback interface is deleted while VPLS auto-discovery is enabled, and more than one
loopback interface is configured on the device, the Brocade device uses the IP address configured
on the next lowest numbered loopback interface as the router ID. For example, using the following
configuration, when loopback interface 1 is deleted, the Brocade device uses loopback interface 2.
Thus, the successive router ID is 10.4.4.4/24. The system removes all existing VPLS routes for
10.9.9.9/24 and obtain new routes for 10.4.4.4/24.
Loopback interface 1, 10.9.9.9/24
Loopback interface 2, 10.4.4.4/24
When a loopback interface is deleted from the configuration while VPLS auto-discovery is enabled,
and there are no other valid loopback interfaces, the system disables LDP and VPLS
auto-discovery.
Adding a loopback interface
To add a loopback interface, enter commands such as the following.
Brocade(config)# int loopback 1
Brocade(config-lbif-1)# ip address 10.1.1.4/24
Syntax: [no] interface loopback num
Use the [no] form of the command to delete a loopback interface. Also refer to “Changes that occur
when a loopback interface is deleted” in the following section.
The num value can be a number from 1 – 64.