Cisco Cisco Nexus 5010 Switch Guida Alla Progettazione

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More on domain-id with Double-Sided vPC Topologies

As described in Chapter 3 “System ID in a vPC System”, the domain-id defined for the vPC domain is used to

generate the system-id of the system comprised of the vPC peers. Because of this it is important to ensure that
each vPC “system” in a topology such as the one illustrated in Figure 7 utilizes a different domain-id number.

This ensures uniqueness in the Bridge ID used for BPDUs and the LAGID used by LACP. Alternatively, as

described in Chapter 3, it is possible to define the same domain-id as long as the user configures manually a

different system-id which uniquely identifies the vPC domain.

Data Center-to-Data Center Connectivity

The multichassis EtherChannel configuration that is often required to connect distant data center sites consists of

four systems: two switching devices per site, connected with a multichassis EtherChannel as depicted in Figure 8.

In Figure 8, there are two data centers, DC1 and DC2. Each site is comprised of two Cisco Nexus 7000 Series

Switches that have a local peer link and a local peer-keepalive link. The two data centers are connected with

two fibers. One fiber connects N7kA-DC1 to N7kC-DC2 and one fiber connects N7kB-DC1 to N7kC-DC2.

An EtherChannel ensures that both links are forwarding and that DC1 and DC2 have Layer 2 connectivity.

Incidentally, the links are secured with Cisco Trusted Security, so what traverses the public space is encrypted

at wire speed at Layer 2.

As Figure 8 indicates, not only are back-to-back PortChannels supported, but also dual layers of PortChannels, in

that each Cisco Nexus 7000 Series system provides vPC toward the other data center and vPC from the access

layer.

When configuring the vPC domain IDs, make sure they differ on data center 1 and data center 2.

Figure 8. Layer 2 Extension Between Data Centers with vPC