Why is the tx-quque-limit set to 26 as default for member links for a multilink bundle when dMLP is enabled on a Cisco 7500?
For any Serial interface of bandwidth T1/E1, the tx-queue-limit is around 4 or 5. When you are bundling T1s/E1s together in multilink, the bandwidth would increase for the bundle. Because switching would take place based on the bandwidth of MLP interface, you need to increase the tx-queue-limit of member links. Only one of the member links, called the primary link, is used for switching, therefore, its tx-queue-limit need to be increased. Also, this value is an empirical one chosen after testing and then tuning to this value. In general, the deployments have not more than 4 to 6 T1/E1 links in a bundle. A value of 26 can cater for 6 to 8 T1/E1 links perfectly, and hence this value was chosen.
