RD value of a VPN instance on S series switches

Traditional BGP cannot process the VPN routes that have overlapping address spaces. Assume that both VPN1 and VPN2 use addresses on the network segment 10.110.10.0/24, and each of them advertises a route destined for this network segment. The local PE identifies the two VPN routes based on VPN instances and sends them to the remote PE. Because routes from different VPNs cannot work in load-balancing mode, the remote PE adds only one of the two routes based on BGP route selection rules. As a result, the route to the other VPN is lost.
To ensure that VPN routes of VPNs with overlapping address spaces are correctly processed, PE devices use MP-BGP to advertise VPN routes and use the VPN-IPv4 address family to identify the routes.
RDs distinguish the IPv4 prefixes with the same address space. IPv4 addresses with RDs are VPN-IPv4 addresses (VPNv4 addresses). After receiving IPv4 routes from a CE, a PE converts the routes to globally unique VPN-IPv4 routes and advertises the routes on the public network.
The following is a configuration example:
#
ip vpn-instance vpna
ipv4-family
route-distinguisher 200:1
vpn-target 111:1 export-extcommunity
vpn-target 111:1 import-extcommunity
#

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