Cisco Cisco IOS Software Release 12.2(33)SRE

The MPLS VPN—VRF CLI for IPv4 and IPv6 VPNs feature has the following prerequisites:

For migration—An IPv4 Multiprotocol Label Switching (MPLS) VPN VRF must exist.

For a new VRF configuration—Cisco Express Forwarding and an MPLS label distribution method, 
either Label Distribution Protocol (LDP) or MPLS Traffic Engineering (TE), must be enabled on all 
routers in the core, including the provider edge (PE) routers.

The MPLS VPN—VRF CLI for IPv4 and IPv6 VPNs feature has the following restrictions:

Once you have converted to a multiprotocol VRF, you cannot convert the VRF back to an IPv4-only 
single-protocol VRF. 

You can associate an interface with only one VRF. You cannot configuring a VRF for IPv4 and a 
different VRF for IPv6 on the same interface.

You can configure only IPv4 and IPv6 address families in a multiprotocol VRF. Other protocols 
(IPX, Appletalk, and the like) are not supported.

Before you use the MPLS VPN—VRF CLI for IPv4 and IPv6 VPNs feature to migrate from a 
single-protocol VRF to a multiprotocol VRF, you should understand the following:

VPNs for IPv6 use the same VRF concepts that IPv4 VPNs use, such as address families, route 
distinguishers, route targets, and VRF identifiers. Customers that use both IPv4 and IPv6 VPNs might 
want to share VRF policies between address families. They might want a way to define applicable VRF 
policies for all address families, instead of defining VRF policies for an address family individually as 
they do for or a single-protocol IPv4-only VRF.

Prior to Cisco IOS Release 12.2(33)SRB, a VRF applied only to an IPv4 address family. A one-to-one 
relationship existed between the VRF name and a routing and forwarding table identifier, between a VRF 
name and a route distinguisher (RD), and between a VRF name and a VPN ID. This configuration is 
called a single-protocol VRF.