The DS3/E3 mapping table associates DS3/E3 channels with logical or physical interfaces.

For example, consider a DS3 device with 16 T1's and 1 VCG. There are 28 logical/internal channels, numbered 1 through 28 but only 17 are actually connected.

We might describe the allocation of channels, in the dsx3MappingTable, as follows: dsx3MappingIfIndex.1. 1 = 1001 dsx3MappingIfIndex.1.15 = 1015 dsx3MappingIfIndex.1. 2 = 1002 dsx3MappingIfIndex.1.16 = 1016 dsx3MappingIfIndex.1. 3 = 1003 dsx3MappingIfIndex.1.17 = 1017 dsx3MappingIfIndex.1. 4 = 1004 dsx3MappingIfIndex.1.18 = 0 dsx3MappingIfIndex.1. 5 = 1005 dsx3MappingIfIndex.1.19 = 0 dsx3MappingIfIndex.1. 6 = 1006 dsx3MappingIfIndex.1.20 = 0 dsx3MappingIfIndex.1. 7 = 1007 dsx3MappingIfIndex.1.21 = 0 dsx3MappingIfIndex.1. 8 = 1008 dsx3MappingIfIndex.1.22 = 0 dsx3MappingIfIndex.1. 9 = 1009 dsx3MappingIfIndex.1.23 = 0 dsx3MappingIfIndex.1.10 = 1010 dsx3MappingIfIndex.1.24 = 0 dsx3MappingIfIndex.1.11 = 1011 dsx3MappingIfIndex.1.25 = 0 dsx3MappingIfIndex.1.12 = 1012 dsx3MappingIfIndex.1.26 = 0 dsx3MappingIfIndex.1.13 = 1013 dsx3MappingIfIndex.1.27 = 0 dsx3MappingIfIndex.1.14 = 1014 dsx3MappingIfIndex.1.28 = 0

Note that in the case above all channels are mapped to one T3 port with ifIndex = 1. The Channels 1...28 are represented via the 2nd index. The values of 1001...1016 are the T1 interface ifIndexes. The value of 1017 is the ifIndex of the VCG. Unconnected channels have a value of 0.