available bandwidth

Yes, that is the default and it indicates that the maximum reservable bandwidth on the interface. The reservation is done when QoS is configured on the system. You can change that using the "max-reserved-bandwidth" command under the interface.

The idea with only allowing 75% of the bandwidth to be reservable by default is to allow 25% for routing protocols and other such important traffic. BTW since you are running EIGRP, you can also look into a command that limits how much of the bandwidth EIGRP is allowed to use. That command is "ip bandwidth-percent eigrp percent ".

Cisco da Gama

I see... I can understand setting aside some of the bandwidth for overhead, but isn't 25% a little much? In case, that comes to about 600 kbit/s. The only routing protocol going over these T1s is EIGRP with a handful of networks.

Are there any kind of guidelines to adjusting this? Would it be better to use max-reserved-bandwidth, or ip bandwidth-percent eigrp? Thanks!

Note that 75% number is just the max reservable bandwidth when you are using QoS. It does not mean that only 75% of the bandwidth will be used. If there is user traffic, it will use the all the bandwidth it can if QoS is not configured. It is just that you cannot use QoS to give bandwidth guarantees beyond 75% if the interface bandwidth unless you increase the reservable bandwidth using the "max-reserved-bandwidth" command.

By default, EIGRP will use no more than 50% of the link bandwidth. If you have an unstable network where you think EIGRP is using too much of your link bandwidth, you can limit that further using the "ip bandwidth-percent eigrp" command to less than 50%. If the network is stable, I would suggest just leaving that alone.

Cisco da Gama

I see... there seems this ceiling at 75% of the bandwidth that we can't seem to get through. I don't think I've ever configured any QoS before. Could something be on by default?

The T1s in question are a full T1 and 14 channels of another one. I expect the theorectical maximum bandwidth to be 2432 kbit/s (38 channels X 64 kbit/s/channel). The peak speed showing up on our router stats is about 1800 kbit/s, about 75% (that was a location to location backup at around 4am when the rest of the network was quiet). During the day, we seem to get an average throughput of 1200 to 1400 kbit/s in the tests that I've done. I don't see any points that seem to be saturated.

Is the throughput we're getting reasonable for the bandwidth we have?

Thanks!