Configure VRRP on 2 aggregation switches

VRRP can be configured on two aggregation switches to provide a highly available default gateway by assigning a shared virtual IP, setting priorities, and enabling preemption and interface tracking.

Overview

VRRP allows multiple switches to share a virtual IP address that acts as the default gateway for connected hosts. One switch becomes the Master, handling traffic for the virtual IP, while the other remains in Standby, taking over if the Master fails . This ensures uninterrupted network connectivity and eliminates a single point of failure.

Basic Configuration Steps

1. Assign IP Addresses to Interfaces
   • Configure each switch with a unique physical IP on the VLAN or SVI that will participate in VRRP.
   • Example:

     interface Vlan10 ip address 192.168.10.2/24 on Switch 1, and

     interface Vlan10 ip address 192.168.10.3/24 on Switch 2 .

2. Configure the VRRP Group
   • Assign a VRRP group number and the virtual IP that hosts will use as their default gateway.
   • Set priority to determine which switch becomes Master (higher priority wins).
   • Enable preemption if you want the higher-priority switch to take over when it comes online.
   • Example:

     vrrp 10 ip 192.168.10.1vrrp 10 priority 110vrrp 10 preempt on the primary switch, and

     vrrp 10 ip 192.168.10.1vrrp 10 priority 100vrrp 10 preempt on the secondary switch .

3. Adjust Advertisement Timers (Optional)
   • Default advertisement interval is 1 second; you can adjust for faster or slower failover:

     vrrp 10 timers advertise 3vrrp 10 preempt delay minimum 60 This delays preemption to prevent flapping .

4. Enable Interface or Object Tracking
   • Track critical interfaces or objects to dynamically adjust VRRP priority if a link goes down:

     vrrp 10 track interface Ethernet1/1 decrement 20 This ensures failover occurs if a key uplink fails .

Considerations for Aggregation Switches

• vPC or MC-LAG Integration
  • When using vPC (Cisco) or MC-LAG (other vendors), configure VRRP on the primary vPC/MC-LAG peer as active and the secondary as standby .
  • VRRP advertisements must traverse the peer link; multicast traffic may not pass correctly if MC-LAG is misconfigured, so ensure the peer link allows VRRP multicast packets .
• Multiple VRRP Groups
  • You can configure multiple VRRP groups per VLAN to provide redundancy for different subnets.
• VRRP Version
  • Use VRRPv3 for IPv4 and IPv6 support and to enable virtual switch redundancy across multiple switches .
• Failover Testing
  • Test by shutting down the Master switch or tracked interfaces to verify the Standby switch takes over the virtual IP correctly.

Example Topology

• Switch 1 (Primary)
  • VLAN 10: 192.168.10.2/24
  • VRRP 10: VIP 192.168.10.1, priority 110, preempt enabled
• Switch 2 (Secondary)
  • VLAN 10: 192.168.10.3/24
  • VRRP 10: VIP 192.168.10.1, priority 100, preempt enabled
• Hosts
  • Default gateway: 192.168.10.1 This setup ensures that if Switch 1 fails, Switch 2 immediately assumes the virtual IP and continues forwarding traffic without disruption.

Best Practices

• Keep VRRP priorities consistent with your intended Master/Standby roles.
• Use interface tracking to prevent failover loops.
• Ensure multicast traffic for VRRP is allowed across all relevant links, especially in MC-LAG or vPC environments.
• Avoid connecting both router interfaces to the same switch if possible; distribute connections across both aggregation switches for true redundancy . By following these steps and considerations, you can configure VRRP on two aggregation switches to provide a resilient, highly available default gateway for your network.