public void replaceNullIDs(VersionSource id) {
    if (memberID == null) {
      memberID = (T) id;
    }
    if (previousMemberID == null && hasPreviousMemberID() && entryVersion > 1) {
      previousMemberID = (T) id;
    }
  }
replace null member IDs with the given identifier. This is used to incorporate version
information into the cache that has been received from another VM
geode-core/src/main/java/org/apache/geode/internal/cache/versions/VersionTag.java