fix

src/router.rs

@@ -18,7 +18,7 @@ impl Router {
     pub fn get(routers: &mut HashMap<u8, Router>, link_address: SocketAddr) -> Option<&mut Router> {
         match link_address {
             SocketAddr::V4(addr) => {
-                let id = addr.ip().octets()[3];
+                let id = addr.ip().octets()[2];
                 routers.get_mut(&id)
             }
             SocketAddr::V6(_) => None,