Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual page 469

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To assign an interface to a VRF from inside the VRF context:
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ip vrf forwarding
Select the interface.
Specify the VRF to associate with the interface.
host1:vr1(config)#interface gigabitEthernet 1/0
host1:vr1(config-if)#ip vrf forwarding vrfA
Assign an IP address to the interface because forwarding the interface from the
VR to the VRF removes the existing IP configuration from the interface.
host1:vr1:vrfA(config-if)#ip address 10.16.2.77 255.255.255.0
Select the interface.
Enter the VRF context.
host1:vr1(config)#virtual-router :vrfA
Associate the interface.
host1:vr1:vrfA(config)#interface gigabitEthernet 1/0
In this case, you do not have to reassign an IP address to the interface because
you did not use the ip vrf forwarding command.
Use to assign a VRF to an interface or subinterface by forwarding the interface
from the VR to the VRF. This command also enables you to specify secondary
routing table lookup for a VRF, in the event that an initial routing table lookup
does not yield results.
Forwarding the interface removes the IP configuration from the interface. You
must reassign an IP address to the interface after you issue this command.
The ip vrf forwarding command changes the prompt to indicate that the CLI is
now in Interface Configuration mode within the child VRF. This condition persists
only for as long as you are configuring attributes on the given interface within
the VRF. Entering a top-level command, such as interface, within this VRF context
takes the CLI out of the VRF context back to the parent VR context.
When you issue the ip vrf forwarding command from within the Interface
Configuration or Subinterface Configuration mode of the parent VR, the IP address
and other attributes of the interface are deleted from the interface. You must
then reconfigure the IP attributes in the context of the VRF after issuing the
command.
Example
host1:foo(config-if)#ip vrf forwarding vrfA
host1:foo:vrfA(config-if)#ip address 10.12.4.5 255.255.255.0
or
host1:foo(config-if)#ip vrf forwarding vrfA fallback global
Chapter 5: Configuring BGP-MPLS Applications
Configuring BGP VPN Services
433