Virtual Private Routed Network Service422FD 100/320Gbps NT and FX NT IHub Services Guide3HH-11985-AAAA-TQZZA Issue: 13The ISAM uses an IGP (RIP, OSPF, ISIS) to exchange the routes of a particular CErouter with the PE routers that are attached to that ISAM. This is done in a way whichensures that routes from different VPNs remain distinct and separate, even if twoVPNs have an overlapping address space.In addition, ISAM uses VPRN to separate traffic from different service providers.Each service provider has his own means to manage the IP addresses, services andthe traffic of its subscribers, even if all the routing is actually done in the scope of theglobal Internet so that subscriber IP subnets never overlap.For this, ISAMs are connected to PE routers and Edge Routers via VLANs.Figure 33 displays a VPRN network example.Figure 33 Virtual Private Routed Network7.2.1 ISAM to PE Route ExchangeRouting information between the ISAM and the Provider Edge (PE) can beexchanged by the following methods:• Static Routes• E-BGP• RIP• OSPFEach protocol provides controls to limit the number of routes learned from each CErouter.Serviceaccess pointVPRNVPRNVPRNISAM7750EMANAccess portVLAN (localscope)IES SAPAccessportVLANVRFbaseVPRN7750VRF baseVRF baseIPIPIPIPIPIPIPIPSAPSAPSAPSAPSAPSAPSAPSAPSAPSAPIP SAPIP SAPIP SAPIP SAP
