Cisco Cisco Nexus 5010 Switch Guida Alla Progettazione
Design Guide
Figure 9.
vPC Doesn’t Introduce Duplicate Frames
Finally, it is also important to realize that a topology based on PortChannels doesn’t introduce loops, even if the peer
link is lost and all the ports are forwarding. Figure 10 explains why.
link is lost and all the ports are forwarding. Figure 10 explains why.
Figure 10 illustrates the worst-case scenario of a vPC dual-active failure when both peer-link and peer-keepalive
connectivity is lost. In this particular case one switch is running spanning tree (switch 4) with links that are not in
PortChannel mode, while the other switches are configured in PortChannel mode. Even with this scenario, the worst
that can happen is duplicate frames.
connectivity is lost. In this particular case one switch is running spanning tree (switch 4) with links that are not in
PortChannel mode, while the other switches are configured in PortChannel mode. Even with this scenario, the worst
that can happen is duplicate frames.
With all links forwarding, a broadcast frame or an unknown unicast generated on switch 4, for example, is forwarded
only on both links directed to switch 1 and switch 2. When these two frames arrive on switch 3, they are not sent back
to the PortChannel because that breaks the basic rule of Layer 2 forwarding—namely, that a frame cannot return to
the port from which it originated.
only on both links directed to switch 1 and switch 2. When these two frames arrive on switch 3, they are not sent back
to the PortChannel because that breaks the basic rule of Layer 2 forwarding—namely, that a frame cannot return to
the port from which it originated.
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