diff --git a/tbsetup/ns2ir/sim.tcl.in b/tbsetup/ns2ir/sim.tcl.in
index 398e5fefaf97337a02a395553ca55f051387134d..bed44100a0b439d6c38fdc92815983026b8ca8b0 100644
--- a/tbsetup/ns2ir/sim.tcl.in
+++ b/tbsetup/ns2ir/sim.tcl.in
@@ -499,6 +499,24 @@ Simulator instproc at {time eventstring} {
   }
 }
 
+#
+# Routing control. Right now, we do not support much at all.
+#
+Simulator instproc rtproto {type args} {
+    var_import ::GLOBALS::default_ip_routing_type
+
+    if {$args != {}} {
+	punsup "rtproto: arguments ignored: $args"
+    }
+
+    if {($type == "Session") ||	($type == "ospf")} {
+	set default_ip_routing_type "ospf"
+    } else {
+	punsup "rtproto: unsupported routing protocol ignored: $type"
+	return
+    }
+}
+
 # unknown 
 # This is invoked whenever any method is called on the simulator
 # object that is not defined.  We interpret such a call to be a