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Monday, September 13, 2010

DMVPN- tunnel transmit (and recieve) bandwidth statements

Should this command be used on a DMVPN multipoint interface (3845 router) where typically over 100 spokes have tunnels terminated? Because the defualt is 8Mb. All of our monitoring tools report that the multipoint tunnel interface is over utilized every work day. We've looked for information about this command and pasted what we found below (which supports our question). But we've found nothing about this in any DMPVN documentation . tunnel bandwidth {receive | transmit} bandwidth receive Specifies the bandwidth to be used to receive packets through the tunnel. transmit Specifies the bandwidth to be used to send packets through the tunnel. bandwidth Bandwidth, in kbps. Range is from 0 to 2147483647. Default is 8000.

Tunnel bandwidth transmit and tunnel bandwidth receive are only used with RBSCP - rate based satellite control protocol. In the document link, in the usage guidelines, it says:"Use the tunnel bandwidth command to specify the capacity of the satellite link."
  • So this doesn't apply to limiting bandwidth. Set the 'bandwidth' command on the tunnel interface to be equal to your ISP link and see if that resolves your issue. It won't change the throughput of of the tunnel, but will allow more routing protocol traffic like EIGRP, which limits itself to 1/2 the defined bandwidth of the tunnel. Hopefully your monitoring tool will see the increased bandwidth and get rid of the message for you. If not, you need to determine what number your tool is pulling down for the 'bandwidth' of the tunnel so you can figure out why it says it's being exceeded.

Please check this link:
  1. Tunnel bandwidth is only used with RBSCP - see the usage guidelines in the documents you are posting and you will see the word 'satellite', which indicates it's for RBSCP. Putting the commands in will change the display output, but will not actually change the transmit/receive rate unless you are using RBSCP.
  2. The second part of my message about the 'bandwidth', was an effort o find a way to stop your tool from reporting your tunnel (which is a virtual interface that has no *actual* bandwidth restrictions when not using rbscp) as being over-subscribed.You'll need to work with your monitoring tool vendor to see where they are pulling the bandwidth/throughput number and how they're determining it's oversubscribed. Most probably they're looking at the bandwidth command/setting on the tunnel interface, but as it's a tunnel interface, that number shouldn't be used in determining whether a tunnel is 'over-subscribed'.

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