Port resources and ISLs

mark.j.smith · ‎07-08-2008

Hi there,

Maybe someone could clarify this for me:

If the bandwidth resources for a 4Gbps port is set to "dedicated", and then ISL'd to another switch which is only 2Gbps capable how much bandwidth is left in the port group ?

Reading the port-resources output is looks like there is only 8.8Gbps (12.8Gbps total minus the 4Gbps that has been dedicated) left to share with the other ports ... even though the port has negotiated to 2Gbps at a physical level ?

Is that a true figure and the blade will share out only 8.8Gbps ? Or will it share out 10.8Gbps ?

Thanks!

dmcloon · ‎07-08-2008

If the remote switch is only 2Gbps capable then you will be setting the local 4Gbps capable port to either "switchport speed 2000" or leave it at default of "switchport speed auto". With the former we will dedicate 2Gbps of bandwidth in port-resources. With the latter we have to allow for the port to negotiate 4Gbps so we will dedicate 4Gbps of bandwidth. Even if it negotiates 2Gbps, the 4Gbps have already been dedicated. If this is a concern simply code "switchport speed 2000" on the 4Gbps capable port.

mark.j.smith · ‎07-08-2008

That's how I thought it worked ... so just to clarify, if it is set to "auto" then 4Gbps get's dedicated .. and that 100% only leaves 8.8Gbps left to the rest of the port group ?

so if all the ports load up the total they use will cap at 8.8Gbps ?

Thanks!

dmcloon · ‎07-08-2008

Correct, 8.8Gbps will be left which can be shared by the rest of the ports in that group.