Руководство По Проектированию для Cisco Cisco Nexus 5010 Switch
Design Guide
© 2010 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information.
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s - Supports-STP-Dispute
Device-ID Local Intrfce Hldtme Capability Platform Port ID
tc-nexus7k01-vdc2(TBM12162254)Eth2/1 158 R S I s N7K-C7010 Eth2/9
tc-nexus7k02-vdc2(TBM12193229)Eth2/2 158 R S I s N7K-C7010 Eth2/9
Cisco Fabric Services over Ethernet Synchronization Protocol
The vPC peers use the Cisco Fabric Services protocol to synchronize forwarding-plane information and implement
necessary configuration checks.
vPC peers must syncrhonize the Layer 2 forwarding table - that is, the MAC address information between the vPC
peers. This way, if one vPC peer learns a new MAC address, that MAC address is also programmed on the Layer 2
forwarding table of the other peer device.
The Cisco Fabric Services protocol travels on the peer link and does not require any configuration by the user.
To help ensure that the peer link communication for the Cisco Fabric Services over Ethernet protocol is always
available, spanning tree has been modified to keep the peer-link ports always forwarding.
The Cisco Fabric Services over Ethernet protocol is also used to perform compatibility checks to validate the
compatibility of vPC member ports to form the channel, to synchronize the IGMP snooping status, to monitor the
status of the vPC member ports, to synchronize the Address Resolution Protocol (ARP) table (starting from Cisco
NX-OS 4.2(6) and future Release 5.0 releases).
If the peer link is disconnected between two vPC peers, the synchronization between vPC peers is interrupted, which
may lead to traffic drop for multicast traffic and to flooding for unicast traffic.
vPC Configuration Changes When the Peer Link Fails
The correct sequence for setting up vPCs requires that the two participating vPC switches see each other over the
peer link and that they can communicate over the vPC peer keepalive link.
Figure 9 illustrates this fundamental concept: the configuration depicted in Figure 9 (2) requires starting from Figure 9
(1). If you try to configure a vPC like in Figure 9 (2) without having established vPC peer-link and vPC peer keepalive
connectivity, vPC ports won’t go into forwarding state.
connectivity, vPC ports won’t go into forwarding state.
Once you are in the state depicted in Figure 9 (1) (which is a fully formed vpc domain) the peer keepalive connectivity
is not strictly required in order to create or modify vPCs. In other words, you can configure the vPC in Figure 9 (2)
even if there’s a loss of vPC peer keepalive connectivity after the configuration depicted in Figure 9 (1).
even if there’s a loss of vPC peer keepalive connectivity after the configuration depicted in Figure 9 (1).
It is necessary and recommended to have functional vPC peer keepalive connectivity for the correct behavior of vPC
in presence of failures, but from a traffic forwarding and configuration purpose, the temporary failure of the peer
keepalive link doesn’t have any impact.
keepalive link doesn’t have any impact.
The vPC peer-link connectivity is more important for the correct traffic forwarding operations as well as for the ability
to create or modify vPCs.