Configuration restrictions and guidelines
When you assign an interface to an HDLC link bundle, follow these restrictions and guidelines:
An interface can belong to only one HDLC link bundle at any point in time. To assign a member interface to another HDLC link bundle, remove the interface from the current HDLC link bundle first.
The link layer protocol of an interface to be assigned to an HDLC link bundle must be HDLC. After the interface is assigned to the HDLC link bundle, its link layer protocol cannot be changed.
You can assign interfaces to a nonexistent HDLC link bundle as members.
You can assign interfaces on different cards to the same HDLC link bundle.
Changing the bundling priority of a member interface might cause the device to determine the state of each member interface.
The peer interface directly connected to a local HDLC link bundle member interface must also join the same HDLC link bundle. A HDLC link bundle ID is locally significant. The ID on the peer device can be different from the local one.
As a best practice, use the bundle member-priority command and the bundle max-active links command together to make sure that:
Interconnected interfaces at both ends can be Selected.
They can exchange traffic correctly.