Update subnet-up.tmpl

tinc/subnet-up.tmpl

@@ -7,6 +7,10 @@ if [ -z "\$nonMACChars" ]; then
   echo "\$SUBNET" > \$macFile
 else
   # This subnet is likely an IP address, add it to the ARP table
-  mac=`cat \$macFile`
-  arp -s "\$SUBNET" "\$mac"
+  if test -f "\$macFile"; then
+    mac=`cat \$macFile`
+    arp -s "\$SUBNET" "\$mac"
+  else
+    echo "WARNING: No MAC known for node \$NODE, can't route \$SUBNET. This is only a problem if this is a remote route."
+  fi
 fi