Peer-Keepalive Link And Messages - Cisco Nexus 3548 Configuration Manual
Nx-os interfaces release 9x
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- Command reference manual (556 pages) ,
- Configuration manual (230 pages) ,
- Installation manual (112 pages)
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Configuring Virtual Port Channels
Peer-Keepalive Link and Messages
You can configure the EtherChannels and vPC peer links by using LACP or no protocol. When possible, we
recommend that you use LACP on the peer-link, because LACP provides configuration checks against a
configuration mismatch on the EtherChannel.
The vPC peer switches use the vPC domain ID that you configure to automatically assign a unique vPC system
MAC address. Each vPC domain has a unique MAC address that is used as a unique identifier for the specific
vPC-related operations, although the switches use the vPC system MAC addresses only for link-scope
operations, such as LACP. We recommend that you create each vPC domain within the contiguous network
with a unique domain ID. You can also configure a specific MAC address for the vPC domain, rather than
having the Cisco NX-OS software assign the address.
The vPC peer switches use the vPC domain ID that you configure to automatically assign a unique vPC system
MAC address. The switches use the vPC system MAC addresses only for link-scope operations, such as LACP
or BPDUs. You can also configure a specific MAC address for the vPC domain.
We recommend that you configure the same VPC domain ID on both peers and, the domain ID should be
unique in the network. For example, if there are two different VPCs (one in access and one in aggregation)
then each vPC should have a unique domain ID.
After you create a vPC domain, the Cisco NX-OS software automatically creates a system priority for the
vPC domain. You can also manually configure a specific system priority for the vPC domain.
Note
If you manually configure the system priority, you must ensure that you assign the same priority value on
both vPC peer switches. If the vPC peer switches have different system priority values, the vPC will not come
up.
Peer-Keepalive Link and Messages
The Cisco NX-OS software uses a peer-keepalive link between the vPC peers to transmit periodic, configurable
keepalive messages. You must have Layer 3 connectivity between the peer switches to transmit these messages;
the system cannot bring up the vPC peer link unless a peer-keepalive link is already up and running.
You can configure a hold-timeout and a timeout value simultaneously.
Hold-timeout value—The hold-timeout value range is between 3 to 10 seconds, with a default value of 3
seconds. This timer starts when the vPC peer link goes down. The purpose of the hold-timeout period is to
prevent false-positive cases.
If you configure a hold-timeout value that is lower than the timeout value, then the vPC system ignores vPC
peer-keepalive messages for the hold-timeout period and considers messages for the reminder of the timeout
period. If no keepalive message is received for this period, the vPC secondary device takes over the role of
the primary device. For example, if the hold-timeout value is 3 seconds and the timeout value is 5 seconds,
for the first 3 seconds vPC keepalive messages are ignored (such as, when accommodating a supervisor failure
for a few seconds after peer link failure) and keepalive messages are considered for the remaining timeout
period of 2 seconds. After this period, the vPC secondary device takes over as the primary device, in case
there is no keep alive message.
Timeout value—The timeout value range is between 3 to 20 seconds, with a default value of 5 seconds. This
timer starts at the end of the hold-timeout interval. If you configure a timeout value that is lower than or equal
to the hold-timeout value, then the timeout duration is initiated after the hold-timeout period. For example, if
the timeout value is 3 seconds and the hold-timeout value is 5 seconds, the timeout period starts after 5 seconds.
Cisco Nexus 3548 Switch NX-OS Interfaces Configuration Guide, Release 9x
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