Do not add the same network multiple times

birdvisu/maps.py

@@ -30,11 +30,13 @@ class Topology:
 				self.network_addrs[directive] = net_addr
 
 		# Fix the topology: find other networks (stubnets, external, ...) and links:
+		known = set()
 		for r, rd in self.routers:
 			for n, nd in rd:
 				if n.startswith(('network', 'stubnet', 'external')):
 					net_id = re.match(r'((network|stubnet|external) [^ ]+)', n).group(1)
-					if n.startswith(('stubnet', 'external')):
+					if n.startswith(('stubnet', 'external')) and net_id not in known:
+						known.add(net_id)
 						self.networks.append((net_id, []))
 						# Add dummy mapping
 						self.network_addrs[net_id] = net_id