DELL N3000 User Manual

Configuring VRRP

The accept mode allows the switch to respond to pings (ICMP Echo 

Requests) sent to the VRRP virtual IP address. The VRRP specification (RFC 

3768) indicates that a router may accept IP packets sent to the virtual router 

IP address only if the router is the address owner. In practice, this restriction 

makes it more difficult to troubleshoot network connectivity problems. When 

a host cannot communicate, it is common to ping the host's default gateway 

to determine whether the problem is in the first hop of the path to the 

destination. When the default gateway is a virtual router that does not 

respond to pings, this troubleshooting technique is unavailable. In the Dell 

Networking switch VRRP feature, you can enable Accept Mode to allow the 

system to respond to pings that are sent to the virtual IP address.
This capability adds support for responding to pings, but does not allow the 

VRRP master to accept other types of packets. The VRRP master responds to 

both fragmented and un-fragmented ICMP Echo Request packets. The 

VRRP master responds to Echo Requests sent to the virtual router's primary 

address or any of its secondary addresses.
Members of the virtual router who are in backup state discard ping packets 

destined to VRRP addresses, just as they discard any Ethernet frame sent to a 

VRRP MAC address. 
When the VRRP master responds with an Echo Reply, the source IPv4 

address is the VRRP address and source MAC address is the virtual router's 

MAC address.

The VRRP Route/Interface Tracking feature extends VRRP capability to allow 

tracking of specific routes and interface IP states within the router that can 

alter the priority level of a virtual router for a VRRP group. 
VRRP interface tracking monitors a specific interface IP state within the 

router. Depending on the state of the tracked interface, the feature can alter 

the VRRP priority level of a virtual router for a VRRP group. 

An exception to the priority level change is that if the VRRP group is the IP 

address owner, its priority is fixed at 255 and cannot be reduced through the 

tracking process.