Dell Networking OS10 How to Use LACP PortChannel for a PXE Boot Client

Sammanfattning: This article explains how to use Link Aggregation Control Protocol (LACP) with clients requiring Preboot execution environment (PXE) boot in OS10 switches.

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Table of Content

Why LACP Fallback is Required
How LACP Fallback Operates
Configuration Syntax
Sample Configuration

 

Why LACP Fallback is Required

LACP PortChannel (LAG) requires the peer-side device to send LACP PDU. However, when clients boot in PXE mode, they cannot send LACP PDUs and the switch does not enable the LACP PortChannel. LACP Fallback feature allows the devices to communicate using a single port in the PortChannel during the PXE boot process.
 

How LACP Fallback Operates

  • When you enable LACP fallback, the switch starts a timer. If the timer expires before LACP completes, then the switch selects one port of the port group and makes it operational. This port is used for the PXE boot process by the client
  • When the switch starts receiving LACP PDU, OS10 ungroups the statically added member port from LACP port channel and resumes with normal LACP functionality.


Fallback Port election

  • LACP port priority configuration allows deterministic port allocation. The port with the least priority is placed in the active state when a PortChannel is in LACP fallback mode.
  • If all the ports in a PortChannel have the same port priority, the switch internally compares the interface names by base name, module number, port number, and then selects the lowest one to be active. For example, Ethernet 1 is less than Ethernet 2 and hence Ethernet 1 becomes active.
  • In a VLT network, if the interface name is the same on both the VLT peers, then the port in switch with the lower system MAC address becomes active
 
NOTE: The fallback port is elected only once during the initial LACP negotiation when a member port is brought up. Expired timers do not retrigger the fallback process until all member links are down and brought up again. Typically this is accomplished through a cold boot of the remote device. LACP Individual feature port does not have this requirement.
 
NOTE: As an alternative to LACP Fallback, you may also use LACP individual port feature. This feature is available from 10.5.3.0. You cannot configure the LACP individual ports and LACP fallback features on a LAG simultaneously as they are mutually exclusive.
 

Configuration Syntax

NOTE: If you are configuring LACP fallback in a VLT domain, configure LACP fallback commands in both the VLT peers.
 

Configuration

Explanation

 
OS10# configure terminal

Enter Configure Mode

 
OS10(config)# interface port-channel X

Configure the PortChannel interface

 
OS10(conf-if-po-X)# lacp fallback enable

Enables LACP fallback mode.

 
OS10(conf-if-po-X)# lacp fallback timeout

(Optional) Configures LACP fallback time-out period. (Default 15 Sec)

 
OS10(conf-if-po-X)# lacp fallback preemption

(Optional) Enables LACP fallback port preemption. (This is by default enable)


Commands to verify the LACP fallback are working.

OS10# show port-channel summary
OS10# show lacp port-channel interface port-channel <portchannel number>

 

Sample Configuration

Assume we are configuring PortChannel 1. The member ports are eth 1/1/1 and eth 1/1/2. We are connected to a Client which requires PXE boot.


PXE Boot Client passing to switch through port channel 1

Configuration

OS10# configure terminal
OS10(config)# interface port-channel 1
OS10(conf-if-po-1)# lacp fallback enable


Use the "show lacp port channel interface port channel 1” command to find the fallback port elected.

 

OS10# show lacp port-channel interface port-channel 1 | grep fallback
Fallback: Configured, Fallback port preemption: Configured, Fallback timeout: 15 seconds
Fallback Port Elected: ethernet1/1/1

 

NOTE: The Fallback port is only elected once LACP PortChannel is down and the timer expires.

Use "show port channel summary" to verify the PortChannel status. 
OS10# show port-channel summary
Flags:  D - Down    I - member up but inactive    P - member up and active
        U - Up (port-channel)    F - Fallback Activated
--------------------------------------------------------------------------------
Group Port-Channel           Type     Protocol  Member Ports
--------------------------------------------------------------------------------
1    port-channel1    (UF)    Eth      DYNAMIC   1/1/1(P) 1/1/2(I)
 

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Artikelegenskaper
Artikelnummer: 000184053
Artikeltyp: How To
Senast ändrad: 13 maj 2024
Version:  4
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