Hi, fractional T3 is more correctly called subrate, that is a clear channel T3 with less bandwith using subrate mode, cisco supports four modes, you have to ask your provider what they are using on their side, and configure accordingly under controller t3;
dsu mode [ 0 | 1 |2 | 3 | 4 ]
* 0 Digital Link or Cisco 300-44210 Kbps
* 1 ADC Kentrox T3/E3 IDSU 1500-35000, 44210 Kbps
* 2 Larscom Access T45 3100-44210 Kbps
* 3 Adtran T3SU 300 75-44210 Kbps
* 4 Verilink HDM 2182 1500-44210 Kbps
dsu bandwidth
Configures the bandwidth for an unchannelized subrate T3 interface.
* bandwidth A Numeric value between 1 and 44210
The default bandwidth is 44210.
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