2. Different mechanisms

To explain the different technical options, we'll take two networks as examples. Three VPNs (one green, one yellow and one purple) are involved in inter-AS, as each customer (green, yellow and purple) has sites in both AS 64500 and AS 64501. AS 64500 is made up of two PE routers (PE1 and PE2) and an ASBR (ASBR1) which links it to AS 64501, itself made up of a PE router (PE3) and an ASBR (ASBR2). Each network includes a (RR) for MP-iBGP session scaling, as shown in figure 3 .