This document suggests the following guidelines for exchanging routing information between BGP-4 and EGP2.
To provide for graceful migration, a BGP speaker may participate in EGP2, as well as in BGP-4. Thus, a BGP speaker may receive IP reachability information by means of EGP2 as well as by means of BGP-4. The information received by EGP2 can be injected into BGP-4 with the ORIGIN path attribute set to 1. Likewise, the information received via BGP-4 can be injected into EGP2 as well. In the latter case, however, one needs to be aware of the potential information explosion when a given IP prefix received from BGP-4 denotes a set of consecutive A/B/C class networks. Injection of BGP-4 received NLRI that denotes IP subnets requires the BGP speaker to inject the corresponding network into EGP2. The local system shall provide mechanisms to control the exchange of reachability information between EGP2 and BGP-4. Specifically, a conformant implementation is required to support all of the following options when injecting BGP-4 received reachability information into EGP2:
The exchange of routing information via EGP2 between a BGP speaker participating in BGP-4 and a pure EGP2 speaker may occur only at the domain (autonomous system) boundaries.