diff --git a/seba-in-a-box/Makefile b/seba-in-a-box/Makefile
index e1430c6..006816f 100644
--- a/seba-in-a-box/Makefile
+++ b/seba-in-a-box/Makefile
@@ -43,7 +43,7 @@
 BBSIM_DHCP_TOSCA ?= examples/bbsim-dhcp.yaml
 
 # Targets
-ponsim: $(M)/siab
+ponsim: validate_args $(M)/siab
 
 bbsim: $(M)/bbsim-tosca
 
@@ -66,6 +66,18 @@
 # Parallel make won't work here; need to install seba-1.0.0 before siab
 siab-1.0: $(M)/seba-1.0.0 $(M)/siab
 
+validate_args:
+	if ! ([[ $(NUM_OLTS) == ?(-)+([0-9]) ]] && [ $(NUM_OLTS) -ge 1 ] && [ $(NUM_OLTS) -le 4 ]); \
+	then \
+		echo "Invalid value: NUM_OLTS must between 1 and 4"; \
+		exit 1; \
+	fi
+	if ! ([[ $(NUM_ONUS_PER_OLT) == ?(-)+([0-9]) ]] && [ $(NUM_ONUS_PER_OLT) -ge 1 ] && [ $(NUM_ONUS_PER_OLT) -le 4 ]); \
+	then \
+		echo "Invalid value: NUM_ONUS_PER_OLT must between 1 and 4"; \
+		exit 1; \
+	fi
+
 $(M)/setup:
 	sudo $(MAKEDIR)/../scripts/portcheck.sh
 	mkdir -p $(M)