--> Broadcast traffic is one type of traffic, in which data is sent from one source to all the destinations.
--> Broadcast address in the network can be of two types,
1) Network Broadcast address: 255.255.255.255 ( This is used to forward the packet to all the devices within the subnet)
2) IP Broadcast Address: Last IP Address of each subnet ( Broadcast address of specific subnet).
--> Routers drop broadcast traffic as soon as they receive that on any interface of the router.
--> IP directed broadcast allows the router to forward the broadcast packet on a particular subnet.
--> IP directed broadcast basically used in wake-on-LAN (WOL) application by forwarding broadcast packets targeted at the hosts in a specified destination subnet.
--> IP directed broadcast packets are sent over the network in the same way as unicast IP packets until they reach the destination subnet.
--> When they reach the destination subnet and IP directed broadcast is enabled on the receiving switch, the switch translates the IP directed broadcast packet into a broadcast that floods the packet on the target subnet.
--> All hosts on the target subnet receive the IP directed broadcast packet.
--> Typically, you do not enable IP directed broadcast on subnets that have direct connections to the Internet.
--> Disabling IP directed broadcast on a subnet’s Layer 3 interface affects only that subnet.
--> If you disable IP directed broadcast on a subnet and a packet that has the broadcast IP address of that subnet arrives at the switch, the switch drops the broadcast packet.
Example:
--> If a device with ip 192.168.1.20/24 is sending broadcast traffic on the subnet by forwarding packets to 192.168.3.255/24.
--> The routers in between the path forwards the packet is similar to the unicast packet if ip direct broadcast is enabled.
--> It can cause DOS attacks and hence it is recommended to disable it.
Configuration on Cisco Devices
Router(config)# Int G0/0
Router(config-if)# ip directed-broadcast
--> Broadcast address in the network can be of two types,
1) Network Broadcast address: 255.255.255.255 ( This is used to forward the packet to all the devices within the subnet)
2) IP Broadcast Address: Last IP Address of each subnet ( Broadcast address of specific subnet).
--> Routers drop broadcast traffic as soon as they receive that on any interface of the router.
--> IP directed broadcast allows the router to forward the broadcast packet on a particular subnet.
--> IP directed broadcast basically used in wake-on-LAN (WOL) application by forwarding broadcast packets targeted at the hosts in a specified destination subnet.
--> IP directed broadcast packets are sent over the network in the same way as unicast IP packets until they reach the destination subnet.
--> When they reach the destination subnet and IP directed broadcast is enabled on the receiving switch, the switch translates the IP directed broadcast packet into a broadcast that floods the packet on the target subnet.
--> All hosts on the target subnet receive the IP directed broadcast packet.
--> Typically, you do not enable IP directed broadcast on subnets that have direct connections to the Internet.
--> Disabling IP directed broadcast on a subnet’s Layer 3 interface affects only that subnet.
--> If you disable IP directed broadcast on a subnet and a packet that has the broadcast IP address of that subnet arrives at the switch, the switch drops the broadcast packet.
Example:
--> If a device with ip 192.168.1.20/24 is sending broadcast traffic on the subnet by forwarding packets to 192.168.3.255/24.
--> The routers in between the path forwards the packet is similar to the unicast packet if ip direct broadcast is enabled.
--> It can cause DOS attacks and hence it is recommended to disable it.
Configuration on Cisco Devices
Router(config)# Int G0/0
Router(config-if)# ip directed-broadcast
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