SEP, Specifying an Interface to Block

Specifying the interface with the highest priority as the blocked   interface

The rules for comparing the priorities of interfaces are as follows:

1.        The interface with the   highest priority is designated as the blocked interface. The priorities of   interfaces can be set. The greater the priority value, the higher the   priority.

2.        If the interfaces have the   same priority, their bridge MAC addresses are compared. The interface with   the lowest bridge MAC address is more likely to be designated as a blocked   interface.

3.        If the interfaces have both   the same priority and bridge MAC address, their interface numbers are   compared. The interface with the smallest interface number is more likely to   be designated as a blocked interface.

Specifying the interface in the middle of a SEP segment as the blocked   interface

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Specifying a blocked interface based on the hop count set by users

The hop count of the primary edge interface is 1, and the hop count from   the primary edge interface to the neighboring interface is 2. Continuing to   move downstream, each downstream neighbor of the primary edge interface   increases the hop count by one.

Specifying a blocked interface based on the device name and interface   name

After SEP is configured, a device name and an interface name are used to   designate the interface to be blocked. Before specifying an interface to   block, run a display command to obtain information about all   interfaces, and then specify the device name and interface name.

If there are several devices with the same device name and interface name   on a ring network, preemption packets search from the device where the   primary edge interface resides and then block the first searched interface   with the specified device name and interface name.

NOTE:

If the device name and interface name are used to specify an interface to   block, changing the device name or interface name will render the preemption   mechanism ineffective.

Non-preemption mode

When the last faulty link   recovers or last two interfaces complete neighbor negotiation, the interface   to be blocked is determined by exchanging packets containing the blocked   status of interfaces. The other   interfaces enter the forwarding state.

Preemption Mode

NOTE:

Preemption can be   implemented only on the device where the primary edge interface resides or   the no-neighbor primary edge interface resides.

The preemption mode is   classified into delayed preemption and manual preemption.

o    Delayed preemption

When the last faulty edge   interface recovers, the edge interface no longer receives fault advertisement   packets. If the primary edge interface receives no fault advertisement packet   within 3 seconds, it starts a delay timer. After the delay timer expires,   nodes in the SEP segment preempt blocked interfaces.

o    Manual preemption

When the manual preemption   mode is configured by using commands and the link status databases of the   primary edge interface and the secondary edge interface are complete, the   elected primary edge interface or the brother interface of no-neighbor   primary edge interface will send preemption packets to block a specified   interface. The interface sends a packet to advertise its status immediately   after being blocked. The interface that is blocked before preemption enters   the forwarding state. Then, manual preemption is complete.

NOTE:

Only two interfaces on a   device can be added to the same SEP segment. If one interface is the   no-neighbor primary edge interface, the other interface is the brother   interface of the no-neighbor primary edge interface.