$78-$ used when a host or a router needs to find the link$-$layer

$($MAC$)$ address of another host or router in its network

a$.$ AGMP

b$.$ ARP

c$.$ ICMP

d$.$ RARP

$79-$ The kink$-$layer broadcast address

a$.00$:$00$:$00$:$00$:$00$:$00$

b$.FF$:$FF$:$FF$:$FF$:$FF$:$FF$

c$\mathrm{.}111\mathrm{.}111\mathrm{.}111\mathrm{.}111$

d$\mathrm{.}127\mathrm{.}0\mathrm{.}0\mathrm{.}1$