- Enterasys Security Router User's Guide

IP Routing Protocols
XSR User’s Guide 5-31
Load Balancing
The XSR provides load balancing according to the following rules:
• Load balancing depends on how your network is designed.
• Load balancing is supported by separate physical VRRP routers and not supported on the
same physical router which has two LAN ports on the same LAN segment with the same
subnet.
ARP Process on a VRRP Router
Three types of ARP requests can be employed on a VRRP router: Host, Proxy and Gratuitous ARP.
Host ARP
Host ARP performs according to the following rules:
• When a host sends an ARP request for one of the VR IP addresses, the master VR returns the
virtual MAC address (00-00-5e-00-01-VRID).
• The backup VR must not respond to the ARP request for one of the VR IP addresses.
• If the master VR is the IP address owner, when a host sends an ARP request for this address,
the master VR must respond with the virtual MAC address, not the real physical MAC address.
• For other IP addresses, the VRRP router must respond with the real physical MAC address,
regardless of master or backup.
Proxy ARP
• If Proxy ARP is used on a VRRP router, then the master VRRP router must advertise the VR
MAC address for the VR IP address in the proxy ARP message.
Gratuitous ARP
Gratuitous ARP behaves in the following manner on a VRRP router:
• Each VR sends gratuitous ARP when it becomes the master with virtual IP and MAC
addresses. One gratuitous ARP is issued per VR IP address.
• To make the bridge learn the correct VR MAC address, the VR masters send gratuitous ARP
for every virtual IP address in the corresponding VR every 10 seconds.
Traffic Process on a VRRP Router
Incoming traffic on a VRRP router is governed by the following rules:
• Whether a VRRP router is in a master or backup state, it must receive packets with a real
physical MAC address as the destination MAC address.
• The master VR must receive packets with a virtual MAC address as the destination MAC
address.
• The backup VR must not receive any packets with the virtual MAC address as the destination
MAC address.
Outgoing traffic on a VRRP router is governed by the following rules: