A directed broadcast is a broadcast intended for all nodes on a nonlocal network. For example, the broadcast address 255.255.255.255 reaches all nodes on a network; the directed broadcast address 128.1.255.255 is intended for all nodes whose network address is 128.1.0.0. A router not directly attached to 128.1.0.0 simply forwards the directed broadcast packet to the next hop. A router on network 128.1.0.0---if it has directed broadcast forwarding enabled---accepts and forwards the packet to all nodes whose network address is 128.1.0.0. Routers connecting subnets of 128.1.0.0 also accept and forward the packet to the nodes on their respective subnets.
IP Redirects enables the sending of redirect messages to end nodes by using ICMP. For instance, you have 2 routers in a local segment and they are servicing different networks. Your default gateway is routerA and routerA have ip routes pointing to routeB. With IP Redirects, routerA is able to redirect the traffic to RouterB.
