States of member interfaces

An HDLC link bundle member interface can be in one of the following states:

• Initial—The member interface is down at the link layer.

• Negotiated—The member interface is as follows:

  • Up at the link layer.

  • Does not meet the conditions for being a Selected interface in the HDLC link bundle.

• Ready—The member interface is as follows:

  • Up at the link layer.

  • Meets the conditions for being a Selected interface.

  • Not Selected yet due to the following restrictions:

    • The maximum number of Selected interfaces.

    • The minimum number of Selected interfaces required for bringing up the HDLC link bundle.

    • The minimum bandwidth required for bringing up the HDLC link bundle.

• Selected—The member interface is up at the link layer, meets the conditions for being Selected, and conforms to the restrictions. Only member interfaces in Selected state can forward traffic.

If an HDLC link bundle does not contain any Selected interfaces, the HDLC link bundle interface is brought down, and it cannot forward traffic. It will not be brought up and forward traffic until Selected interfaces are detected in the HDLC link bundle. The bandwidth of an HDLC link bundle interface is the total bandwidth of all Selected interfaces.

The states of HDLC link bundle member interfaces are determined according to the following rules:

1. An interface is placed in the Initial state if its link layer protocol is down.

2. An interface is placed in the Negotiated state when its link layer protocol goes up.

3. An interface in the Negotiated state might transit to the Selected or Ready state after completing the following selection process.

4. For example:

   • The number of member interfaces in the Negotiated state is M.

   • The maximum number of Selected interfaces allowed in the HDLC link bundle is set to N.

   The maximum number of Selected member interfaces allowed in a bundle is set by using the bundle max-active links command. If the command is not set or the set value exceeds the hardware capability, the hardware capability applies.

   • When N is no smaller than M, all the member interfaces in the Negotiated state enter the Selected state.

   • When N is smaller than M, these member interfaces are sorted as follows:

     • They are first sorted in the descending order of rates/baud rates.

     • Member interfaces with the same rate/baud rate are sorted in the descending order of bundling priorities.

     • Member interfaces with the same bundling priority are sorted in the ascending order of interface numbers.

     The first N member interfaces enter the Selected state, and the remaining (M-N) member interfaces enter the Ready state.

5. For example, the number of member interfaces meeting the conditions for being Selected is P. The minimum number of Selected interfaces required for bringing up the HDLC link bundle is set to Q.

   The P interfaces will be Selected when any of the following conditions exist:

   • P is not smaller than Q.

   • The following limits are not set:

     • Minimum number of Selected interfaces required for bringing up the HDLC link bundle.

     • Minimum bandwidth required for bringing up the HDLC link bundle.

   None of the P member interfaces will be Selected and they all stay in the Ready state when any of the following conditions exist:

   • P is smaller than Q.

   • The total bandwidths of the P member interfaces is smaller than the minimum bandwidth required for bringing up the HDLC link bundle.