A virtual template interface is used to provide the configuration for dynamically created virtual access interfaces. Once the virtual template interface is created, it can be configured in the same way as a serial interface. Virtual template interfaces can be created and applied by various applications such as Virtual Profiles, virtual private dialup networks (VPDN), PPP over ATM, protocol translation, and Multichassis Multilink PPP (MMP). Interface multilink is a command introduced in 12.0 which is used to combine multiple links like multiple T1s to increase the bandwidth of the channel. refer this link for more information :
http://www.cisco.com/en/US/products/sw/iosswrel/ps1826/products_configuration_guide_chapter09186a00800d9bd9.html
