2 Replies Latest reply: May 22, 2019 8:44 PM by Martin RSS

    IP Static routes with "permanent" word in the syntax

    Mihai

      Hello ,

       

      I've just read in the ICND! 100-105 book about the method with "permanent" ip static route .

       

      My question is , as in packet tracer we can't do this exercise , do the route appears in the routing table even if the interface is down ?

       

      Can anyone post a photo where the route is still present , but the interface is down ?

       

      Best regards,

      Mihai

         
        • 1. Re: IP Static routes with "permanent" word in the syntax
          Phoenix

          Hi Mihai,

           

          Here is a simple topology with static route permanent configuration.

          • Initially, after configuring static route for remote LAN network, there are two routes in the routing table for R2.
            • 1- Static route
            • 2- Directly connected route

          static-1.PNG

           

          • Now, I'll shut down the R2's F0/0 port but because of 'permanent' keyword , static route will still be present in the routing table

          static-2.PNG

          • Ping from R2 to remote PC-1 will fail obviously but as you can see route is still present for this destination.

          static-3.PNG

           

          Hope this help...

           

          Cheers!!!

          • 2. Re: IP Static routes with "permanent" word in the syntax
            Martin

            Yes, route appears in the routing table even if the interface is down


            router does recursive lookup to match network to outgoing interface; aka for each network in routing table, there must be exit interface.  Sometimes router must do recursive lookup twice. i.e. network x is via next hop z, which is via interface xyz.

             

            if interface or next hop goes down (is not available), network is removed from table.

            if u add "permanent" into static route statement, such route will stay in table if thou next hop is unavailable or interface is down.

            this is done sometimes if there are other ways to reach next hop.