I'm studying towards the CCNA exam and am currently reading the ICND2 book.
In chapter 3 (p 147), we're given an example under predicting normal operation of the LAN switching data plane. Specifically, the example covers a PC broadcasting in a VLAN through three routers (configured in a 'triangular connection') to a router which is located the other side two of the routers.
The text says:
"The first working data plane example examines the path of a broadcast sent by PC1. PC1 might not have R1's MAC address in PC1's ARP cache, so in that case, PC1 sends an ARP broadcast with an IP destination of 255.255.255.255 and an Ethernet destination address of FFFF.FFFF.FFFF. This section examines what the various switches do to forward the broadcast..."
What I'm having difficulty understanding is why, if PC1 is trying to find the MAC address of the router, the ARP destination IP address is set as the broadcast IP and not the IP address of the router?
My understanding is that normally an ARP will be sent to a specific IP address, with a destination Ethernet address of FFFF.FFFF.FFFF. I also thought that a gratuitous ARP request has the both the source and destination IP addresses set to that of the sender. Neither of these cases cover an ARP with a destination IP address of the network broadcast address.
As I currently understand it, broadcast ARPs do not get responded to, is this right?
Having worked through the example, it does not state or otherwise imply that on receipt of the ARP by R1 that R1 will respond (and I would hope that it wouldn't, as long as my understanding is correct).
Is there something about ARPs sent to a broadcast address that I haven't picked up on? Do routers automatically respond to a broadcast ARP with their own IP and MAC address to the sender?