Example 2: Classic and Fabric-Enabled System
The following output is from a configuration with dual supervisor engines, one SFM, one classic line card in slot 3, and two fabric-enabled line cards in slots 7 and 9.
Sup-A> (enable) show fabric channel switchmode
Module Num Fab Chan Fab Chan Switch Mode Channel Status
------ ------------ -------- ------------ --------------
1 | 1 | 0, 0 flow through ok |
2 | 1 | 0, 1 | truncated | ok |
3 | 0 | n/a | n/a | n/a |
5 | 18 | 0, 0 | n/a | | ok |
5 | 18 | 1, 1 | n/a | | ok |
5 | 18 | 2, 2 | n/a | | unknown |
5 | 18 | 3, 3 | n/a | | unknown |
5 | 18 | 4, 4 | n/a | | unknown |
5 | 18 | 5, 5 | n/a | | unknown |
5 | 18 | 6, 6 | n/a | | ok |
5 | 18 | 7, 7 | n/a | | unknown |
5 | 18 | 8, 8 | n/a | | ok |
5 | 18 | 9, 9 | n/a | | unknown |
5 | 18 | 10, 10 n/a | | unknown |
5 | 18 | 11, 11 n/a | | unknown |
5 | 18 | 12, 12 n/a | | unknown |
5 | 18 | 13, 13 n/a | | unknown |
5 | 18 | 14, 14 n/a | | unknown |
5 | 18 | 15, 15 n/a | | unknown |
5 | 18 | 16, 16 n/a | | unknown |
5 | 18 | 17, 17 n/a | | unknown |
7 | 1 | 0, 6 | truncated | ok |
9 | 1 | 0, 8 | truncated | ok |
15 | 0 n/a | n/a | | n/a |
16 | 0 n/a | n/a | | n/a |
Automatic switching mode changes allow the acceptance of classic or fabric-enabled cards into a system with no manual configuration change. As previously stated, there is a performance versus interoperability tradeoff when installing classic line cards into a fabric-enabled system. Because many network environments hold performance in higher regard, a fabric-enabled system can be configured to reject classic cards (for example, not support flow-through mode). By issuing the set system crossbar-fallback none command, the system will not start classic line cards installed in the chassis, thereby running in compact switching mode (30 Mpps) only.
Sup-A> (enable) set system crossbar-fallback none
The default for the crossbar-fallback is bus mode. To determine the current system state, the show system crossbar-fallback
command is available.
Sup-A> (enable) show system crossbar-fallback
Cross-fallback: bus-mode
In summary, the SFM can be redundantly configured in a chassis to provide fabric-to-fabric and fabric-to-bus failover. A system configured with dual SFMs can use the standby SFM for failover. Additionally, single SFM systems with fabric-enabled line cards can fail over to the 32-Gbps bus for continuous operation. In both of these scenarios, recovery and return to normal operation occur in less than three seconds. This quick recovery time allows for a switching mode change and a synchronization process that must take place between each line card, supervisor engine, and the SFM fabric channels in these scenarios. The capability to configure redundant SFMs provides up to three levels of backplane redundancy, helping to enable continuous operations with minimal impact to network availability in the event of a hardware failure.
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