Hello Martin
Your observation is correct. In HSRP and GLBP, the Virtual IP responds to pings, but in VRRP, it does not. This is based on the way the protocol itself is designed. The reason for this is clearly stated in RFC 3768 which defines VRRP.
Unlike HSRP, VRRP can use either a non-assigned IP address as the virtual IP (as configured in the lesson), or it can use an IP address that is owned by one of the redundant routers as the virtual IP. In this case, the “IP Address Owner” is defined as the router that has been assigned the same address that is used as the virtual address. In such a case, the IP address owner also becomes the master device.
Now the RFC states the following:
The Master:
MUST NOT accept packets addressed to the IP address(es) associated
with the virtual router if it is not the IP address owner.MUST accept packets addressed to the IP address(es) associated
with the virtual router if it is the IP address owner.
So in a scenario like the one in the lesson, if you ping the virtual IP address, then the router MUST NOT accept packets addressed to the virtual IP addresses. So pings will be ignored. However, if you configured the virtual IP address as one of the real assigned addresses on one of the routers, then those packets will be accepted and the pings will be responded to.
So to summarize, if the destination IP is that of the IP Address Owner, the ping will be responded to. If the virtual address does not belong to one of the routers, then it will not respond to pings.
Why is this? Well, the RFC gives the following reason:
Potential Forwarding Loop
A VRRP router SHOULD not forward packets addressed to the IP
Address(es) it becomes Master for if it is not the owner. Forwarding
these packets would result in unnecessary traffic. Also in the case
of LANs that receive packets they transmit (e.g., token ring) this
can result in a forwarding loop that is only terminated when the IP
TTL expires.
I hope this has been helpful!
Laz