Cisco Cisco IOS Software Release 12.2(8)YN

For additional information about service provider ISDN switches, refer to the document 

Cisco IOS Release 12.2(8)YN on the Cisco ICS 7750 supports up to 48 channels of voice traffic on the 
same MRP300, in either of the following configurations:

One VWIC-2MFT-T1 (the other MRP300 slot must be empty)

Two VWIC-1MFT-T1s

In order to support 48 voice channels on the same MRP300, that MRP300 can serve only as a voice 
gateway—that is, that MRP300 cannot be configured to provide VLAN routing or any other data 
networking functions. 

In order to support 48 voice channels, it is recommended that a PVDM-256K-16 be installed in each 
PVDM slot, because 4 DSPs must be available to each T1 (assuming that the G.711 codec is being used).

The maximum number of voice channels supported on ASIs and on other MRPs is as follows:

ASI81—38 channels (8 FXS channels + 30 E1 channels)

ASI160—16 channels (16 FXS channels)

MRP200—34 channels (4 FXS or FXO channels + 30 E1 channels)

MRP3-8FXOM1—38 channels (8 FXO channels + 30 E1 channels)

MRP3-8FXS—38 channels (8 FXS channels + 30 E1 channels)

Cisco IOS Release 12.2(8)YN on the Cisco ICS 7750 makes it possible to control the grouping of DSPs, 
by adding support for the [no] tdm connected command. Entering this command on an MRP controls 
the number of DSP groups that are created when there is only one T1 or E1 voice clocking domain.

That is, if a tdm connected command has not been entered, the default configuration would be such that 
there are two DSP groups, provided that there is some combination of analog, BRI, T1, or E1 ports 
installed in the MRP.  If a tdm connected command has been entered, the following DSP groups are 
created, regardless of the types of ports that are installed in the MRP:

Single voice T1 or E1 clocking domain—One DSP group

Two voice T1 or E1 clocking domains—Two DSP groups

When tdm connected has been configured on an MRP, if a subsequent tdm clock command is entered 
that configures a port for voice (or for voice and data), or if the MRP reboots, then a single DSP group 
will be created, regardless of the combination of analog, T1, or E1 ports that is installed, except when 
there are two T1 voice clocking domains.