Four I P Broadcast Address Talk to Edit - Computer Farmers Source - China Protocol Analysis Network Time - 2004-4-28
The restricted broadcast restricted broadcast address is 2 5 5. 2 5 5. 2 5 5. This address is used for the destination address of the I P datagram during the host configuration. At this time, the host may still not know the network mask of its network, and even its I P address does not know. In any case, the router does not forward the datagram of the destination address as the restricted broadcast address, such a datagree report only in the local network. An unfolbened problem is: If a host is a multi-interface, when a process sends a data report to this network broadcast address, whether the broadcast should send the datagram to each connected interface? If this is not the case, the application that broadcasts all interfaces of the host must determine all interfaces that support broadcasts in the host and send a datagram to each interface. Most B S D systems will be 2 5 5. 2 5 5. 2 5. 2 5 5 as a broadcast address of the first interface, and does not provide the function of transmitting a datagram to the interface that is broadcast. . However, R O U T E d (see 1 0. 3) and R W H o D (B S D R W H O Customer Server) is two applications that send U D p datag report to each interface. . Both the two applications use similar startup processes to determine all of the interfaces in the host and understand which interfaces have broadcast capabilities. At the same time, the broadcast address of the pointing network corresponding to the interface is used as the destination address of the data report to the interface. The Host Requirements RFC does not further involve the multi-interface host to send a restricted broadcast to all of its interfaces. The broadcast address of the network pointing to the network is the address of the network. The Class A network broadcast address is N e t i d. 2 5 5. 2 5 5. 2 5 5, where n e t i d is the network number of the Class A network. A router must forward the broadcast of the network, but it must have a choice that is not forwarded. The broadcast address of the subnet is the network of the subnet is the host number 1 and has an address of a specific subnet number. The I P address of the subnet direct broadcast address needs to understand the mask of the subnet. For example, if the router receives a data report to 1 2 8. 1. 2. 2 5 5, the subnet mask of the B network 1 2 8. 1 is 2 5 5. 2 5 5. 2 5 5. At 0, the address is the broadcast address of the subnet; however, if the mask of the subnet is 2 5 5. 2 5 5. 2 5 4. 0, this address is not a broadcast address of the subnet. Pointing to all subnets to point to all subnets, also requires a subnet mask of the network to distinguish from the broadcast address of the network. The subnet number and host number pointing to all subnet broadcast addresses are all 1. For example, if the target subnet mask is 2 5 5. 2 5 5. 2 5 5. 0, then I P Address 1 2 8. 1. 2 5 5. 2 5 5 is a broadcast address pointing to all subnets. However, if the network is not divided into subnet, this is a broadcast to network. Current view [almquist 1993] is that this broadcast is old, better way to use multicast instead of broadcasting all the subnets. [ALMQUIST 1993] Indicates that RFC 922 is required to transfer a broadcast to all subnets to all subnets, but the current router does not do this. This is fortunate, because an host that does not have a subnet mask due to error configuration will pass its local broadcast to all subnets. For example, if the I P address is 1 2 8. 1. 2. 3 The host does not set a subnet mask, its broadcast address is in normal case of 1 2 8. 1. 2 5 5. 2 5 5 . However, if the subnet mask is set to 255.255.255.0, the broadcast from the error configured host will point to all subnets. 1 9 8 3 years of advent of 4. 2 B S D is the first implementation of a wide range of T c P / I P, which uses the host number total 0 as a broadcast address.
