Dynamic Versus Static SPX Configuration

A static PE unit has saved configuration in startup configuration flash. The PE unit continues to exist if the system reloads. A PE unit with dynamic configuration does not have its configuration stored in startup flash. Consequently, the dynamically configured PE configuration is removed when the system reloads.

For example, when PE 18 joins a CB and the CB does not have a reserved configuration for SPX unit 18, the CB generates a new configuration. The PE is a dynamic PE unit until the configuration is saved to startup flash. If SPX unit 18 leaves the system before its configuration is saved, the CB removes SPX unit 18 configuration.

You can change the configuration of an SPX port or LAG for a dynamically learned PE unit. The system changes the unit from dynamic to static. If the PE unit leaves the Campus Fabric domain, the system retains the static configuration. When you change the configuration of a dynamic unit (that is, a unit whose configuration has not been saved to startup flash), the system keeps your changes as part of the dynamic configuration. As a result, if the PE unit leaves and rejoins the Campus Fabric domain, you do not need to modify the configuration again. A static configuration is retained when the unit leaves the domain; however, it may still be lost after a reload if you have not saved it by using the write memory command.

In Provisional-PE mode or in PE mode before the unit joins a CB, you can enter the write memory command to save the configuration as a static configuration in the PE startup file. Once the PE unit has joined a CB, the write memory command can be entered only from the CB. When the CB runs the write memory command, it sends a message to the PE unit that causes it to save the configuration in the PE startup file.

The show spx command identifies static ("S") and dynamic ("D") PE units. If a dynamic PE unit leaves the Campus Fabric domain, the unit is no longer present in command output. In contrast, if a PE unit with a static configuration leaves the domain, its configuration is still displayed in show spx command output, and its status is indicated as "Reserve." The following example shows one reserved PE configuration that has previously been saved (unit 17) and one dynamic PE unit (unit 18).

ICX7750-26Q Router# show spx
T=3h16m53.6: alone: standalone, D: dynamic cfg, S: static
ID   Type          Role    Mac Address   Pri State  Comment
1  S ICX7750-26QXG active  cc4e.2438.7280 0  local   Ready
2  S ICX7750-26QXG member  0000.0000.0000 0  reserve
3  S ICX7750-26QXG standby 748e.f8f9.6300 0  remote  Ready
17 S ICX7450-24G   spx     0000.0000.0000 0  reserve
18 D ICX7750-26QXG spx     cc4e.2438.7500 0  remote  Ready
active standby
+---+        +---+
| 1 |2/4--2/1| 3 |
+---+        +---+
          +----+
1/2/1--2/4| 18 |1/10=
          +----+