ATM Advanced Integration Module (AIM) modules installed in 2600/3600/3700 routers require some unique clocking configuration to allow it to function properly. Failure to configure it properly results in errors on the T1/E1 controller and Inverse Multiplexing (IMA) links, as well as groups that flap continuously.
http://www.cisco.com/en/US/docs/ios/12_2/12_2x/12_2xb/feature/guide/ft_gins2.html
Configure a network clock source and participation for each WIC and AIM module installed. Packet voice and video are sensitive to time delays. To prevent mismatches and data slips, you must synchronize data flows to a single clock source, known as the network clock. When a network clock is configured on a gateway, the router externally clocks one T1 or E1 port, then passes that clock signal across the backplane to another T1 or E1 port on another WIC or network module slot. Use of a network clock on a gateway is configured by naming the network modules and interface cards that are participating in network clocking, and then selecting a controller to act as the source of timing for the network clock.
The network clock provides timing from the source through the controller to the AIM, and then out to all participating router slots. Cisco 2600 series routers support one internal AIM slot, and Cisco 3660 routers support two internal AIM slots. An AIM slot connects to both the main system bus and a secondary time-division multiplexing (TDM) bus running between network module slots and, on the Cisco 2600 series, to WAN interface card (WIC) slots.
For example, on a 2600 series switch with an AIM-ATM module and two VWICs used for IMA, configure as shown:
network-clock-participate wic 0
network-closck-participate wic 1
network-clock-select 1 T1 0/0
On the 2611, 2621, and 2651 the network-clock-participate aim 0 is not required or supported. On the 2691, 3600 or 3700 then you must also include the network-clock-participate aim X command for each installed AIM-ATM module.
