diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index 6365938..6f854d8 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -1128,6 +1128,7 @@
 	BSC_CTR_PAGING_ATTEMPTED,
 	BSC_CTR_PAGING_DETACHED,
 	BSC_CTR_PAGING_RESPONDED,
+	BSC_CTR_UNKNOWN_UNIT_ID,
 };
 
 static const struct rate_ctr_desc bsc_ctr_description[] = {
@@ -1140,6 +1141,8 @@
 	[BSC_CTR_PAGING_ATTEMPTED] = 		{"paging:attempted", "Paging attempts for a subscriber."},
 	[BSC_CTR_PAGING_DETACHED] = 		{"paging:detached", "Paging request send failures because no responsible BTS was found."},
 	[BSC_CTR_PAGING_RESPONDED] = 		{"paging:responded", "Paging attempts with successful response."},
+
+	[BSC_CTR_UNKNOWN_UNIT_ID] = 		{"abis:unknown_unit_id", "Connection attempts from unknown IPA CCM Unit ID."},
 };
 
 
diff --git a/src/libbsc/bts_ipaccess_nanobts.c b/src/libbsc/bts_ipaccess_nanobts.c
index d5b3b21..823fd66 100644
--- a/src/libbsc/bts_ipaccess_nanobts.c
+++ b/src/libbsc/bts_ipaccess_nanobts.c
@@ -468,6 +468,7 @@
 		LOGP(DLINP, LOGL_ERROR, "Unable to find BTS configuration for "
 			" %u/%u/%u, disconnecting\n", dev->site_id,
 			dev->bts_id, dev->trx_id);
+		rate_ctr_inc(&bsc_gsmnet->bsc_ctrs->ctr[BSC_CTR_UNKNOWN_UNIT_ID]);
 		return NULL;
 	}
 	DEBUGP(DLINP, "Identified BTS %u/%u/%u\n",