6.4. EID Reachability within a LISP Site

6.4. EID Reachability within a LISP Site

A site may be multihomed using two or more ETRs. The hosts and infrastructure within a site will be addressed using one or more EID-Prefixes that are mapped to the RLOCs of the relevant ETRs in the mapping system. One possible failure mode is for an ETR to lose reachability to one or more of the EID-Prefixes within its own site. When this occurs when the ETR sends Map-Replies, it can clear the R-bit associated with its own Locator. And when the ETR is also an ITR, it can clear its Locator-Status-Bit in the encapsulation data header.

It is recognized that there are no simple solutions to the site partitioning problem because it is hard to know which part of the EID-Prefix range is partitioned and which Locators can reach any sub-ranges of the EID-Prefixes. This problem is under investigation with the expectation that experiments will tell us more. Note that this is not a new problem introduced by the LISP architecture. The problem exists today when a multihomed site uses BGP to advertise its reachability upstream.