diff --git a/ompi/mca/coll/base/coll_tags.h b/ompi/mca/coll/base/coll_tags.h
index f40f029fbb..2bcf2a6cc9 100644
--- a/ompi/mca/coll/base/coll_tags.h
+++ b/ompi/mca/coll/base/coll_tags.h
@@ -43,6 +43,8 @@
 #define MCA_COLL_BASE_TAG_SCATTERV -26
 #define MCA_COLL_BASE_TAG_NONBLOCKING_BASE -27
 #define MCA_COLL_BASE_TAG_NONBLOCKING_END ((-1 * INT_MAX/2) + 1)
+#define MCA_COLL_BASE_TAG_NEIGHBOR_BASE  (MCA_COLL_BASE_TAG_NONBLOCKING_END - 1)
+#define MCA_COLL_BASE_TAG_NEIGHBOR_END   (MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 1024)
 #define MCA_COLL_BASE_TAG_HCOLL_BASE (-1 * INT_MAX/2)
 #define MCA_COLL_BASE_TAG_HCOLL_END (-1 * INT_MAX)
 #endif /* MCA_COLL_BASE_TAGS_H */
diff --git a/ompi/mca/coll/basic/coll_basic_neighbor_allgather.c b/ompi/mca/coll/basic/coll_basic_neighbor_allgather.c
index 8f79b43d87..9bb1e360fe 100644
--- a/ompi/mca/coll/basic/coll_basic_neighbor_allgather.c
+++ b/ompi/mca/coll/basic/coll_basic_neighbor_allgather.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
  *                         Corporation.  All rights reserved.
- * Copyright (c) 2004-2016 The University of Tennessee and The University
+ * Copyright (c) 2004-2019 The University of Tennessee and The University
  *                         of Tennessee Research Foundation.  All rights
  *                         reserved.
  * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
@@ -70,7 +70,7 @@ mca_coll_basic_neighbor_allgather_cart(const void *sbuf, int scount,
         if (MPI_PROC_NULL != srank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv(rbuf, rcount, rdtype, srank,
-                                    MCA_COLL_BASE_TAG_ALLGATHER,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim,
                                     comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
 
@@ -78,7 +78,7 @@ mca_coll_basic_neighbor_allgather_cart(const void *sbuf, int scount,
             /* remove cast from const when the pml layer is updated to take
              * a const for the send buffer. */
             rc = MCA_PML_CALL(isend((void *) sbuf, scount, sdtype, srank,
-                                    MCA_COLL_BASE_TAG_ALLGATHER,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1,
                                     MCA_PML_BASE_SEND_STANDARD,
                                     comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
@@ -89,13 +89,13 @@ mca_coll_basic_neighbor_allgather_cart(const void *sbuf, int scount,
         if (MPI_PROC_NULL != drank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv(rbuf, rcount, rdtype, drank,
-                                    MCA_COLL_BASE_TAG_ALLGATHER,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1,
                                     comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
 
             nreqs++;
             rc = MCA_PML_CALL(isend((void *) sbuf, scount, sdtype, drank,
-                                    MCA_COLL_BASE_TAG_ALLGATHER,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim,
                                     MCA_PML_BASE_SEND_STANDARD,
                                     comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
diff --git a/ompi/mca/coll/basic/coll_basic_neighbor_allgatherv.c b/ompi/mca/coll/basic/coll_basic_neighbor_allgatherv.c
index f837109f90..37d97970a3 100644
--- a/ompi/mca/coll/basic/coll_basic_neighbor_allgatherv.c
+++ b/ompi/mca/coll/basic/coll_basic_neighbor_allgatherv.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
  *                         Corporation.  All rights reserved.
- * Copyright (c) 2004-2016 The University of Tennessee and The University
+ * Copyright (c) 2004-2019 The University of Tennessee and The University
  *                         of Tennessee Research Foundation.  All rights
  *                         reserved.
  * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
@@ -69,13 +69,14 @@ mca_coll_basic_neighbor_allgatherv_cart(const void *sbuf, int scount, struct omp
         if (MPI_PROC_NULL != srank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv((char *) rbuf + disps[i] * extent, rcounts[i], rdtype, srank,
-                                    MCA_COLL_BASE_TAG_ALLGATHER, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
 
             /* remove cast from const when the pml layer is updated to take
              * a const for the send buffer. */
             nreqs++;
-            rc = MCA_PML_CALL(isend((void *) sbuf, scount, sdtype, srank, MCA_COLL_BASE_TAG_ALLGATHER,
+            rc = MCA_PML_CALL(isend((void *) sbuf, scount, sdtype, srank,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1,
                                     MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
@@ -83,11 +84,12 @@ mca_coll_basic_neighbor_allgatherv_cart(const void *sbuf, int scount, struct omp
         if (MPI_PROC_NULL != drank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv((char *) rbuf + disps[i+1] * extent, rcounts[i+1], rdtype, drank,
-                                    MCA_COLL_BASE_TAG_ALLGATHER, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
 
             nreqs++;
-            rc = MCA_PML_CALL(isend((void *) sbuf, scount, sdtype, drank, MCA_COLL_BASE_TAG_ALLGATHER,
+            rc = MCA_PML_CALL(isend((void *) sbuf, scount, sdtype, drank,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim,
                                     MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
diff --git a/ompi/mca/coll/basic/coll_basic_neighbor_alltoall.c b/ompi/mca/coll/basic/coll_basic_neighbor_alltoall.c
index c5103860e0..6d6468174f 100644
--- a/ompi/mca/coll/basic/coll_basic_neighbor_alltoall.c
+++ b/ompi/mca/coll/basic/coll_basic_neighbor_alltoall.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
  *                         Corporation.  All rights reserved.
- * Copyright (c) 2004-2016 The University of Tennessee and The University
+ * Copyright (c) 2004-2019 The University of Tennessee and The University
  *                         of Tennessee Research Foundation.  All rights
  *                         reserved.
  * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
@@ -37,6 +37,10 @@
 #include "coll_basic.h"
 #include "ompi/mca/topo/base/base.h"
 
+/**
+ * We only have 1024 tags for the neighbor collective, so for now we only support
+ * 512 dimensions.
+ */
 static int
 mca_coll_basic_neighbor_alltoall_cart(const void *sbuf, int scount, struct ompi_datatype_t *sdtype, void *rbuf,
                                       int rcount, struct ompi_datatype_t *rdtype, struct ompi_communicator_t *comm,
@@ -68,7 +72,7 @@ mca_coll_basic_neighbor_alltoall_cart(const void *sbuf, int scount, struct ompi_
         if (MPI_PROC_NULL != srank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv(rbuf, rcount, rdtype, srank,
-                                    MCA_COLL_BASE_TAG_NONBLOCKING_BASE - 2 * dim,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim,
                                     comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
@@ -78,7 +82,7 @@ mca_coll_basic_neighbor_alltoall_cart(const void *sbuf, int scount, struct ompi_
         if (MPI_PROC_NULL != drank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv(rbuf, rcount, rdtype, drank,
-                                    MCA_COLL_BASE_TAG_NONBLOCKING_BASE - 2 * dim - 1,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1,
                                     comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
@@ -105,7 +109,7 @@ mca_coll_basic_neighbor_alltoall_cart(const void *sbuf, int scount, struct ompi_
              * a const for the send buffer. */
             nreqs++;
             rc = MCA_PML_CALL(isend((void *) sbuf, scount, sdtype, srank,
-                                    MCA_COLL_BASE_TAG_NONBLOCKING_BASE - 2 * dim - 1,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1,
                                     MCA_PML_BASE_SEND_STANDARD,
                                     comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
@@ -116,7 +120,7 @@ mca_coll_basic_neighbor_alltoall_cart(const void *sbuf, int scount, struct ompi_
         if (MPI_PROC_NULL != drank) {
             nreqs++;
             rc = MCA_PML_CALL(isend((void *) sbuf, scount, sdtype, drank,
-                                    MCA_COLL_BASE_TAG_NONBLOCKING_BASE - 2 * dim,
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim,
                                     MCA_PML_BASE_SEND_STANDARD,
                                     comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
diff --git a/ompi/mca/coll/basic/coll_basic_neighbor_alltoallv.c b/ompi/mca/coll/basic/coll_basic_neighbor_alltoallv.c
index 8449778140..e963dc2541 100644
--- a/ompi/mca/coll/basic/coll_basic_neighbor_alltoallv.c
+++ b/ompi/mca/coll/basic/coll_basic_neighbor_alltoallv.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
  *                         Corporation.  All rights reserved.
- * Copyright (c) 2004-2016 The University of Tennessee and The University
+ * Copyright (c) 2004-2019 The University of Tennessee and The University
  *                         of Tennessee Research Foundation.  All rights
  *                         reserved.
  * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
@@ -68,14 +68,14 @@ mca_coll_basic_neighbor_alltoallv_cart(const void *sbuf, const int scounts[], co
         if (MPI_PROC_NULL != srank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv((char *) rbuf + rdisps[i] * rdextent, rcounts[i], rdtype, srank,
-                                    MCA_COLL_BASE_TAG_ALLTOALL, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
 
         if (MPI_PROC_NULL != drank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv((char *) rbuf + rdisps[i+1] * rdextent, rcounts[i+1], rdtype, drank,
-                                    MCA_COLL_BASE_TAG_ALLTOALL, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
     }
@@ -98,14 +98,14 @@ mca_coll_basic_neighbor_alltoallv_cart(const void *sbuf, const int scounts[], co
             nreqs++;
             /* remove cast from const when the pml layer is updated to take a const for the send buffer */
             rc = MCA_PML_CALL(isend((char *) sbuf + sdisps[i] * sdextent, scounts[i], sdtype, srank,
-                                    MCA_COLL_BASE_TAG_ALLTOALL, MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1, MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
 
         if (MPI_PROC_NULL != drank) {
             nreqs++;
             rc = MCA_PML_CALL(isend((char *) sbuf + sdisps[i+1] * sdextent, scounts[i+1], sdtype, drank,
-                                    MCA_COLL_BASE_TAG_ALLTOALL, MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim, MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
     }
diff --git a/ompi/mca/coll/basic/coll_basic_neighbor_alltoallw.c b/ompi/mca/coll/basic/coll_basic_neighbor_alltoallw.c
index 9060c82c10..29abb45625 100644
--- a/ompi/mca/coll/basic/coll_basic_neighbor_alltoallw.c
+++ b/ompi/mca/coll/basic/coll_basic_neighbor_alltoallw.c
@@ -3,7 +3,7 @@
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
  *                         Corporation.  All rights reserved.
- * Copyright (c) 2004-2016 The University of Tennessee and The University
+ * Copyright (c) 2004-2019 The University of Tennessee and The University
  *                         of Tennessee Research Foundation.  All rights
  *                         reserved.
  * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
@@ -65,14 +65,14 @@ mca_coll_basic_neighbor_alltoallw_cart(const void *sbuf, const int scounts[], co
         if (MPI_PROC_NULL != srank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv((char *) rbuf + rdisps[i], rcounts[i], rdtypes[i], srank,
-                                    MCA_COLL_BASE_TAG_ALLTOALL, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
 
         if (MPI_PROC_NULL != drank) {
             nreqs++;
             rc = MCA_PML_CALL(irecv((char *) rbuf + rdisps[i+1], rcounts[i+1], rdtypes[i+1], drank,
-                                    MCA_COLL_BASE_TAG_ALLTOALL, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
     }
@@ -95,14 +95,14 @@ mca_coll_basic_neighbor_alltoallw_cart(const void *sbuf, const int scounts[], co
             nreqs++;
             /* remove cast from const when the pml layer is updated to take a const for the send buffer */
             rc = MCA_PML_CALL(isend((char *) sbuf + sdisps[i], scounts[i], sdtypes[i], srank,
-                                    MCA_COLL_BASE_TAG_ALLTOALL, MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim - 1, MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
 
         if (MPI_PROC_NULL != drank) {
             nreqs++;
             rc = MCA_PML_CALL(isend((char *) sbuf + sdisps[i+1], scounts[i+1], sdtypes[i+1], drank,
-                                    MCA_COLL_BASE_TAG_ALLTOALL, MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
+                                    MCA_COLL_BASE_TAG_NEIGHBOR_BASE - 2 * dim, MCA_PML_BASE_SEND_STANDARD, comm, preqs++));
             if (OMPI_SUCCESS != rc) break;
         }
     }