Dell EMC Networking OS10 How to Configure the Preempt Feature in VRRP Version 2 and 3
Summary: This Article explains how to configure Preempt and its behavior in VRRP Version 2 and Version 3
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Symptoms
What is Preempt
Preempt forces the system to change the primary router if another router with a higher priority comes online.
By default Preempt is enabled in OS10 (Both VRRP Version 2 and VRRP Version 3).
Behavior with Preemption Enabled
1. If a higher VRRP Priority switch comes up. Preemption causes that switch to become the primary.
2. If both switches have the same priority and if the current primary goes down. The current backup becomes the primary switch. When the original primary comes up it will be the new backup.
3. If the priority is the same, a change in the IP address to a higher IP on the backup switch will not cause the current primary to become the backup switch.
4. If the priority is the same, a change in the IP address to a higher IP in the current primary causes a reelection, and it becomes the backup switch.
5. If the priority is the same, adding a new switch will not cause the current primary to become the backup switch.
6. If we are using VRRP in VLT nodes, we can use both VLT nodes as active-active (enabled by default.). In Active-Active mode both the VLT nodes of a domain always continue to forward data plane traffic.
Configuration
| Command | Parameter |
| OS10#configure terminal | Enter into switch configuration mode |
| OS10(config)# interface | Enter Interface information (Vlan id, ethernet, portchannel ). |
| OS10(conf-if-XXXXXX)# vrrp-group X | Configure VRRP group identification number |
| OS10(conf-if-XXXXXX)# preempt | Enable Preempt (By Default Enabled). |
| OS10(conf-if-XXXXXX)# no preempt | Disable Preempt |
Cause
Sample Configuration
OS10# configure terminal
OS10(config)# interface vlan 1
OS10(conf-if-vl-1)# ip address 10.0.0.1/24
OS10(conf-if-vl-1)# vrrp-group 1
OS10(conf-vlan1-vrid-1)# virtual-address 10.0.0.254
OS10(conf-vlan1-vrid-1)# no preempt
Resolution
Verify Preempt State
1> Preempt Enabled
OS10(conf-if-vl-1)# do show vrrp brief
Interface Group Priority Preempt State Version Primary addr(s) Virtual addr
---------------------------------------------------------------------------------------------------------------------
vlan1 IPv4 1 100 true primary-state 2 10.0.0.2 10.0.0.254
2>Preempt Disabled
OS10(conf-vlan1-vrid-1)# do show vrrp brief
Interface Group Priority Preempt State Version Primary addr(s) Virtual addr
---------------------------------------------------------------------------------------------------------------------
vlan1 IPv4 1 100 false primary-state 2 10.0.0.2 10.0.0.254
Affected Products
PowerSwitch S3048-ON, PowerSwitch S4048-ON, Dell EMC Networking MX5108n, Dell EMC Networking MX9116n, PowerSwitch S4048T-ON, PowerSwitch S4112F-ON/S4112T-ON, PowerSwitch S4128F-ON/S4128T-ON, PowerSwitch S4148F-ON/S4148T-ON/S4148FE-ON
, PowerSwitch S4248FB-ON /S4248FBL-ON, PowerSwitch S5212F-ON, PowerSwitch S5224F-ON, PowerSwitch S5232F-ON, PowerSwitch S5248F-ON, PowerSwitch S5296F-ON, PowerSwitch S6100-ON, PowerSwitch Z9100-ON, PowerSwitch Z9264F-ON, SmartFabric OS10 Software
...
Article Properties
Article Number: 000135491
Article Type: Solution
Last Modified: 11 Oct 2023
Version: 5
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