2013-11-21 12:44:42.985 [error] <0.4200.0> gen_server <0.4200.0> terminated with reason: no case clause matching {ok,undefined} in riak_repl2_fscoordinator_serv:handle_protocol_msg/2 line 186
So, either riak_repl2_ip:get_matching_address/2 is return undefined when it shouldn't, or riak_repl2_fscoordinator_serv should handle undefined as a valid return.
Line in question: https://github.com/basho/riak_repl/blob/1.4.3/src/riak_repl2_fscoordinator_serv.erl#L186
Eveutally that calls down to:
https://github.com/basho/riak_repl/blob/1.4.3/src/riak_repl2_fscoordinator_serv.erl#L257
So, either riak_repl2_ip:get_matching_address/2 is return undefined when it shouldn't, or riak_repl2_fscoordinator_serv should handle undefined as a valid return.