Index: trunk/src/plugins/rt_topo/crbs_cdt.c
===================================================================
--- trunk/src/plugins/rt_topo/crbs_cdt.c	(revision 1420)
+++ trunk/src/plugins/rt_topo/crbs_cdt.c	(revision 1421)
@@ -34,7 +34,7 @@
 
 #warning TODO: use libualloc for ctn
 static int add_c_edge_cnt;
-#define ADD_C_EDGE(p1, p2) \
+#define ADD_C_EDGE(p1, p2, immut) \
 do { \
 	e = cdt_insert_constrained_edge(cdt, p1, p2); \
 	e->data = obj; \
@@ -49,6 +49,7 @@
 		ctn->old = 1; \
 		gl = grbs_line_realize(&crbs->grbs, tn, cp1->gpt, cp2->gpt); \
 		gl->user_data = ctn; \
+		gl->immutable = immut; \
 		printf("GT 2net_new _c_edge_%d %f %f from P%ld to P%ld\n", add_c_edge_cnt++, cop, clr, cp1->gpt->uid, cp2->gpt->uid); \
 	} \
 } while(0) \
@@ -60,6 +61,7 @@
 	double dx = p2->pos.x - p1->pos.x, dy = p2->pos.y - p1->pos.y;
 	double len2 = dx*dx + dy*dy;
 	cdt_t *cdt = &crbs->cdt;
+	int immut = 1; /* because constrained in the cdt, we do not ever want these to move in grbs */
 
 	if (len2 > maxlen2) {
 		double d, len, x, y;
@@ -81,15 +83,15 @@
 			p = crbs_make_point(crbs, x, y, cop, clr, NULL, net);
 			if (p == NULL)
 				continue;
-			ADD_C_EDGE(lp, p);
+			ADD_C_EDGE(lp, p, immut);
 			lp = p;
 		}
 
 		/* end */
-		ADD_C_EDGE(lp, p2);
+		ADD_C_EDGE(lp, p2, immut);
 	}
 	else
-		ADD_C_EDGE(p1, p2);
+		ADD_C_EDGE(p1, p2, immut);
 }
 
 void rt_topo_crbs_cdt_init(rtrnd_t *ctx, crbs_t *crbs)