Cisco Cisco Nexus 5010 Switch Guida Alla Progettazione
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Figure 9. Etherchannel Misconfiguration Guard
When Switch1 and Switch2 are configured as a vPC system, Cisco Catalyst Switch3 and Switch4 see the BPDU
coming only from one port: the port connecting to the primary vPC switch. Alternatively, when the vPC peer
switches are disconnected (dual-active scenario), both start generating BPDUs, at which point EtherChannel
misconfiguration guard intervenes to shut down the links connecting to the Cisco Nexus switches because in this
case Switch1 and Switch2 would generate BPDUs with different Bridge IDs.
Because of this EtherChannel misconfiguration guard on the Cisco Catalyst platforms used to interfere with the
vPC dual-active failure scenarios whereby two Cisco Nexus switches that were previously forming a vPC system
are losing connectivity on both the peer link and the peer keepalive link. Starting from Cisco NX-OS 4.2 this
problem doesn’t exist any more.
problem doesn’t exist any more.
Note: The misconfiguration guard is not really required in the case of a vPC dual-active failure, because there is
no remaining connectivity between Switch1 and Switch2; thus, this protection does not need to be implemented.
no remaining connectivity between Switch1 and Switch2; thus, this protection does not need to be implemented.
This protection is also unnecessary when the vPC peer keepalive link is up, because vPC implements a recovery
mechanism that shuts down vPC member ports on the secondary vPC peer.
If running a Cisco NX-OS release prior to 4.2 and to reduce the effect on production traffic, disable the
EtherChannel misconfiguration protection (or dispute mechanism) as shown here on the access-layer switches if
they run Cisco Catalyst switches and Cisco IOS Software (you do not need to do this on Cisco NX-OS devices):
no spanning-tree etherchannel guard misconfig