I have a 2801 router with two vpn tunnels going to two other sites. They share a T-1 (1.544mbps) link. When I perform a "sh int tu21", it shows 100k which I noticed today when I was on my management station.
1) Why is this?
2) Should I set the bw manually using the "bandwidth" command?
This is a bit of a surprise to me seeing the bandwidth of a tunnel at 100K, if it has not been set in the configuration. In my experience the bandwidth of tunnel interfaces usually is about 8K. The MTU is also surprisingly large for a tunnel. It would be interesting to see the configuration of the tunnel and of the physical interface which it uses.
You certainly could set the bandwidth using the bandwidth command. But before you spend the energy changing the configuration (and trying to configure what is the best value to use) I suggest that you try to supply an answer to the question about what difference it will make. Bear in mind that the configured bandwidth does not have any effect on the speed or performance of the interface. If you are running OSPF or EIGRP over the tunnel then they will use the bandwidth to calculate the metric. (But how valid or accurate is that metric? Since we do not know how many hops or what kind and what speed media it crosses, then how do we come up with an accurate number for the metric?) If you are running EIGRP over the tunnel then the bandwidth exerts some constraint on the rate at which EIGRP will send updates over the tunnel. The calculation of utilization in your network monitoring applications may use this value (and is subject to the same question about what is an appropriate value mentioned in conjunction with routing metric). Other than these is there a reason why you are concerned with the value of the bandwidth on this tunnel?
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