9 Replies Latest reply: Dec 21, 2013 2:02 PM by Chandan Singh Takuli RSS

    Overlap Error




      in routes why i cannot set two ip address in same network on two serial interfaces ?


      for example if i set on S0/0

      and set on S0/1


      i got overlap S0/0 error



        • 1. Re: Overlap Error
          just plain old Kev

          it has to do with your mask, which determines the range of ip addresses for a subnet.


          you are probably using a /30 which gives you .1 and .2 -- that is for point to point.


          each interface on the router needs to be in a different subnet.

          • 2. Re: Overlap Error

            Dear Hany ,

                                  Kev is right , It can't be the same address on both point-to-point links.May be you should try /28 on one serial interface and /29 on another .

            • 3. Re: Overlap Error

              On s0/0 ip


              but when i try to set on S0/1 ip address


              i got


     overlaps with Serial0/0



     overlaps with Serial0/ overlaps with Serial0/0
              • 4. Re: Overlap Error

                If you have subnetted the  network with  /24 mask and if your result is that as the starting network range , try to assign on s0/0 as is the network itself .In the second case use or on s0/1.

                • 5. Re: Overlap Error
                  just plain old Kev

                  /24 covers the whole range of ip in the last octet, but /29 covers part of it as well.


                  This will always result in overlap if you try to configure those on the same router.


                  I recommend you join the ccent and ccna forums for help...also you need a good study book to review ip subnetting.


                  You can also go to this link to see all the forums latest posts on one page:


                  • 6. Re: Overlap Error

                    This little exercise may help you understand routing

                    1.       Say Hani is data sitting in his living room (network) which is 10.0.0.---something--- 1 to 255

                    2.       And he wants to go to the kitchen (network) which is 10.0.1.---something--- 1 to 255

                    3.       Now the route or exit you take to leave the living room has a number above it, this would be s0/0/0 mask

                    4.       Now you are inside hallway leading to the kitchen (This is a router)

                    5.       To get to the kitchen (that other network) you need exit s0/0/1 and it needs to be a different network mask

                    6.       What you tried to do with your question was “leave” or “route” the network

                    7.       But, the destination you were headed to was, which is the same network.

                    8.       SO, you wanted to leave the living room, walk through the hallway, until you reached the living room.

                    9.       This is your overlap error

                    If you had 2 routers, then it would have been okay to have routerA fa0/0 and routerB fa0/0 and both with a fa0/1 as (connecting them together)

                    1.       Now the route can be completed by leaving through routerA

                    2.       Moving from routerA to routerB

                    3.       Then returning by means of routerB

                    • 7. Re: Overlap Error
                      just plain old Kev

                      look at this thread, there is a link to a chart that shows subnet ranges and where they overlap.


                      • 8. Re: Overlap Error

                        Thanks all for help i really do appreicated it


                        I figured out the problem


                        I have to delete all networks with the same subnet in all interfaces so i would able to set network range for example /30 if i want to set network for 2 available hosts in two direct connected routers but i cannot have /24 on interface and another interface /30



                        • 9. Re: Overlap Error
                          Chandan Singh Takuli

                          Hi Hany


                          You can have /24 & /30 on same router but the network address of both networks must not be same. As router is a layer 3 device it connects 2 different networks. so 2 ports of a router cannot be in same network.