7 Replies Latest reply: Aug 29, 2012 11:46 PM by kpathri RSS

    Intervlan routing in Packet tracer.

    kpathri

      Hi All,

       

      I created two vlans with two L2 switches and one layer 3 switch in packet tracer. However i am able to ping from pc in one vlan to pc in other vlan with out "ip routing" command in L3 switch. i heard that in layer 3 switch we should enable the command "ip routing" for intervlan routing. Is it true? If so why i am able to ping from 10.100 to 20.0.0.100. I thought "ip routing" is enabled by default in layer 3 switch and i disabled the command with "no ip routing". But still i am able to ping from 10.0.0.100 to 20.0.0.100. So here i want to know is this an issue with PT or how can i stop intervlan routing in layer 3 swithc.

       

      Please see the attached PT file. If facing any problem in opening the file please open the document from open-file----etc of packet tracer.

       

      Thank you in advance.

        • 1. Re: Intervlan routing in Packet tracer.
          AshwinR

          Yes, on a Layer 3 Switch, you manually need to turn on IP routing.

           

          When I turn off IP routing on the L# switch the ping it not successfull anymore. Did you do it correctly (turn of IP routing)?

           

          The commands are:

          conf t

          #no ip routing

           

           

          This is my output:

          PC>ping 20.0.0.100

          Pinging 20.0.0.100 with 32 bytes of data:

          Request timed out.
          Reply from 20.0.0.100: bytes=32 time=17ms TTL=127
          Reply from 20.0.0.100: bytes=32 time=8ms TTL=127
          Reply from 20.0.0.100: bytes=32 time=8ms TTL=127

          Ping statistics for 20.0.0.100:
              Packets: Sent = 4, Received = 3, Lost = 1 (25% loss),
          Approximate round trip times in milli-seconds:
              Minimum = 8ms, Maximum = 17ms, Average = 11ms

           

          After turning off IP routing on the L3 switch:

          PC>ping 20.0.0.100

          Pinging 20.0.0.100 with 32 bytes of data:

          Request timed out.
          Request timed out.
          Request timed out.
          Request timed out.

          Ping statistics for 20.0.0.100:
              Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

          PC>

          • 2. Re: Intervlan routing in Packet tracer.
            boro

            Instead of shuting down ip routing I would use access lists to prevent intervlan routing.

             

             

            /b

            • 3. Re: Intervlan routing in Packet tracer.
              cadetalain

              Hi,

               

              there is indeed a problem with PT because when issuing no ip routing the show ip route output still shows the connected Vlan subnets which it shouldn't, yet you can't ping between the hosts anymore which is normal behaviour so it seems it is a cosmetic bug.

              But as boro said to prevent intervlan routing you should be better using access-list like this:

              access-list 100 deny ip 10.0.0.0 0.0.0.255 20.0.0.0 0.0.0.255

              access-list 100 permit ip any any

               

              int vlan 10

              ip access-group 100 in

               

              Regards.

               

              Alain

              • 4. Re: Intervlan routing in Packet tracer.
                boro

                Assuming that ip routing is switched off.

                Routing table would still exist with direct connected networks?

                Routing table would be intact?

                Or routing table with be cleared or switched off?

                 

                /b

                 

                 

                I have switched off routing on my home router ;-)

                It seems that table still exist but is cleared.

                 

                /b

                • 5. Re: Intervlan routing in Packet tracer.
                  Martin

                  Guys, some commands do not work on PT; no ip routing or ip classfull do not work;

                   

                  this is what switch shows:

                   

                  SW1(config)#no ip routing

                  SW1(config)#^Z

                  SW1#sh ip ro

                  *Mar  1 05:12:22.406: %SYS-5-CONFIG_I: Configured from console by console

                  SW1#sh ip ro

                  Default gateway is not set

                   

                  Host               Gateway           Last Use    Total Uses  Interface

                  ICMP redirect cache is empty

                  SW1#

                  • 6. Re: Intervlan routing in Packet tracer.
                    cadetalain

                    Hi,

                     

                    look at the output posted by Martin in his latest reply, this is how it should be with ipv4 routing turned off.

                     

                    Regards.

                     

                    Alain

                    • 7. Re: Intervlan routing in Packet tracer.
                      kpathri

                      Ashwin,

                       

                      Thanks for the reply. I checked this multiple times but ping was successful for so many attempts with and without ip routing. But after certain attempts it stopped pinging with out ip routing. After my task is finished then only i posted in CLN to check is this a bug in PT.  I believe this as the bug.

                       

                      Regards,

                      Kiran.