5 Replies Latest reply: Mar 10, 2011 1:10 AM by anjaz@123 RSS

    Bandwidth command on the tunnel Interface


      Hello All,

      In my Network environment we used to set the bandwith for all GRE& IPSec tunnels.


      I have to understand more about the usage of Bandwidth command on the tunnel Interface.


      For instance, If I set the bandwidth as 3 MB for a tunnel, Does it mean that tunnel capicity is 3 MB and it will allow only 3 MB?


      Any suggestion would appreciable on this regard.




        • 1. Re: Bandwidth command on the tunnel Interface
          Keith Barker - CCIE RS/Security, CISSP

          Hello Thiyag-


          The bandwidth statement doesn't make data move faster or slower by itself, but it can be used by some technologies.


          For example, EIGRP and OSPF can look at the bandwidth parameter (either the default, or the configured one), as part of the calculation for the metric or cost of that link/interface.  


          The bandwidth can also be referenced in QoS applications.  


          On some IOS versions, GRE tunnels got a super small default bandwidth by default, and protocols like EIGRP doesn't want to use all the bandwidth for routing updates, and may not operate correctly with the default.    Another possibly, is that the GRE tunnel may never be used, as the metric is too high, due to default bandwidth that is too small, and that would be another reason for increasing it.


          Best wishes,



          • 2. Re: Bandwidth command on the tunnel Interface

            Hi Thi


            It is used by show int command as well when displaying utilisation.


            Regards Conwyn

            • 3. Re: Bandwidth command on the tunnel Interface

              Hi Keith,

              Bandwidth in Network Communication referes to the amount of data that can be transferred in a particular period from one source to destination.

              In cisco world with the increase in network speed also     increases the bandwidth capabilities i.e. we have default value to set to     1500 bytes now how does we know whether the ISP side supports how much of     MTU



              Ping<IP address> -l 1500 -f


              -l represents send buffer size

              Here-f represents don't fragment flag is set


              In router also we can do this type of ping for that we need to use the followingcommand :-

              Ping<Ip Address> size 1400 df-bit


              thus we can increase the bandwidth capabilities of our router thereby increases the throughput. thus it is necessary to find the bandwidth of ISP side to have a better throughput.


              Please correct me if i'am misundestood the point.....




              • 4. Re: Bandwidth command on the tunnel Interface

                Hi Anjaz


                You mis-understood the point. We are talking about GRE tunnels defaulting to 19K and how you can code any value you want but it is used by the routing protocols.


                To address your point different technologies have different segment sizes for example Token Ring, FDDI, PoS


                Regards Conwyn

                • 5. Re: Bandwidth command on the tunnel Interface

                  Thanks Conwyn for making it clear............ i got misunderstood with the GRE tunnels...