IP Routing for VPRN Services in Nokia SR OS
What this domain tests
The IP routing domain checks whether you can place a VPRN (Virtual Private Routed Network) into the SR OS routing model: a separate routing instance with its own interfaces, routing table, and PE-CE adjacencies. You must know how MP-BGP carries VPN-IPv4/VPN-IPv6 routes, why the route distinguisher (RD) exists, and how route targets (RTs) control import and export.
Core rules
- A VPRN is a VRF. Its interfaces are bound to SAPs or spoke SDPs, not to core ports.
- The RD is prepended to a customer prefix to make it unique in BGP; it does not choose the VRF.
- Export RTs are attached on the originating PE; import RTs on the receiving PE decide which VPRN table accepts the route.
- PE-CE routing can be static, eBGP, OSPF, or IS-IS. The VPRN has its own route preference and ECMP behavior.
- BGP next-hop resolution uses the transport tunnel (LDP, RSVP-TE, or SR), not the VPRN IGP.
Worked example
CE-A in VPRN 100 advertises 10.10.0.0/24 to PE1 over eBGP. PE1 adds RD 192.0.2.1:100, attaches export RT 65000:100, and sends a VPNv4 update to PE2. PE2's VPRN 100 is configured with import RT 65000:100, so it installs the route. A second VPRN 200 on PE2 with import RT 65000:200 does not install it, even if it has the same prefix. If VPRN 200 also imports 65000:100, both VRF tables can hold the prefix because the RDs differ.
Traps
Do not treat RD as a VRF selector. Do not assume an RT configured under a VRF automatically filters both directions. Check route preference when a static and a BGP route compete, and verify that the BGP next hop resolves over a core tunnel.