Cisco WS-X6708-10G-3CXL= - 10 Gigabit Ethernet Module Manual de usuario descargar pdf (Pagina 19)

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Figure 12. Multichassis Cisco EtherChannel Links

Like regular Cisco EtherChannel interfaces, all ports within the multichassis Cisco EtherChannel link have the same

source index regardless of the chassis in which they are physically present, making it possible to apply a single IP

address for Layer 3 Cisco EtherChannel links or for Spanning Tree Protocol to view such a Cisco EtherChannel

interface as a single, logical port.

One unique difference between multichassis Cisco EtherChannel and regular Cisco EtherChannel interfaces is the

way traffic is load balanced across the channel group members. A regular Cisco EtherChannel link selects the

appropriate channel group member to exit based purely on the hashing algorithm of choice. A multichassis Cisco

EtherChannel link, however, has some extra intelligence to reduce the amount of traffic that requires transmission

across the VSL. This optimization is accomplished by populating the index port only with the ports local to the

physical chassis, allowing the chassis to favor the local ports of the multichassis Cisco EtherChannel link over those

on the remote chassis.

For traffic that must be flooded on the VLAN (broadcasts, multicasts, and unknown unicasts), a copy is sent across

the VSL to be sent out any single-homed ports belonging to the VLAN. Because the first chassis will have sent a copy

out one of the multichassis Cisco EtherChannel ports, packets received from the VSL are not sent out of another

multichassis Cisco EtherChannel port. If all of the multichassis Cisco EtherChannel ports on a given chassis are

removed because of a failure, management control, and so on, the Cisco EtherChannel link is no longer a

multichassis Cisco EtherChannel link, but a regular Cisco EtherChannel link, and hence flooded packets will be sent

out of this EtherChannel link from the VSL.

Although the data traffic is spread across the two chassis, the active supervisor engine must terminate control traffic

for the multichassis Cisco EtherChannel link on the active virtual switch, including most of the Layer 2 protocols such

as Spanning Tree Protocol, Port Aggregation Protocol (PAgP), VLAN Trunking Protocol (VTP), and so on. All

multichassis Cisco EtherChannel links have their control protocols terminated on the active supervisor engine. Any

control protocols received by multichassis Cisco EtherChannel link ports on the standby virtual switch are redirected

to the active supervisor engine through the VSL. Because the Cisco EtherChannel link is terminated in one chassis,

PAgP and LACP have the same device identifier on all the member links, regardless of the chassis on which the link

resides.

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Cisco WS-X6708-10G-3CXL= - 10 Gigabit Ethernet Module Manual de usuario Pagina 19