What Clock Combinations Are Possible for Channelized T1/E1/ISDN PRI Drop and Insert?

When you configure the drop-and-insert feature on a channelized T1/E1/ISDN PRI PIM, you must ensure that both ports run on the same clock. The following clock combinations are valid:

• When port 0 is configured to use the internal clock, port 1 must also be configured to use the internal clock.
• When port 0 is configured to use the external clock, port 1 must be configured to run on the same clock, the external clock for port 0.
• When port 1 is configured to use the external clock, port 0 must be configured to run on the same clock, the external clock for port 1.

Services Routers connected to one another must have complementary clock sources configured. Consider a scenario where Router R1 is connected to Routers R2 and R3. Port 0 on the channelized T1/E1/ISDN PRI PIM of R1 is connected to R2, and port 1 is connected to R3. The drop-and-insert feature is configured on R1 to insert input coming from R2 on port 0 into port 1 for transmission to R3.

Routers R1, R2, and R3 can be configured in three ways, according to whether the drop-and-insert clock source on R1 is the external clock for port 0, the external clock for port 1, or the router's internal clock.

To configure the drop-and-insert interfaces on Router R1 to use the external clock for port 0:

1. On Router R2, configure:

2. On Router R3, configure:

3. On Router R1, configure:

To configure the drop-and-insert interfaces on Router R1 to use the external clock for port 1:

1. On Router R2, configure:

2. On Router R3, configure:

3. On Router R1, configure:

To configure the drop-and-insert interfaces on Router R1 to use the router's internal clock:

1. On Router R2, configure:

2. On Router R3, configure:

3. On Router R1, configure: