Руководство По Проектированию для Cisco Cisco Nexus 5010 Switch
Design Guide
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Figure 5. vPC Components with the Fabric Extender (FEX)
To summarize, a vPC system consists of the following components:
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Two peer devices: the vPC peers, of which one is primary and one is secondary; both are part of a vPC
domain
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A Layer 3 Gigabit Ethernet link called a peer-keepalive link to resolve dual-active scenarios
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A redundant 10 Gigabit Ethernet PortChannel called a peer link which is used to carry traffic from one system
to the other when needed and to synchronize forwarding tables
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vPC member ports forming the virtual PortChannel
Traffic Flows
vPC configurations are optimized to help ensure that traffic through a vPC-capable system is symmetric. In Figure 6,
for example, the flow on the left (in blue) reaching a Cisco Nexus switch (Agg1 in the figure) from the core is
forwarded toward the access layer switch (Acc1 in the figure without traversing the peer Cisco Nexus switch device
(Agg2). Similarly, traffic from the server directed to the core reaches a Cisco Nexus Switch (Agg1), and the receiving
Cisco Nexus Switch routes this traffic directly to the core without unnecessarily passing it to the peer Cisco Nexus
device. This process occurs regardless of which Cisco Nexus device is the primary HSRP device for a given VLAN.