internetprotocol(ppt45)-經(jīng)營管理-預(yù)覽頁
【正文】 Range 00000000 = 0 00100000 = 32 01000000 = 64 01100000 = 96 10000000 = 128 10100000 = 160 11000000 = 192 11100000 = 224 TOTAL 6 SUBNETS 8190 HOSTS PER SUBNET Netword ID FROM ISP No. of Network = 1 SUBNET MASK No. of Hosts = 65534 (2^162) We need 6 Subs 255 255 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 224 。 C Defining a Sub Mask Defining a Sub IDs Defining a Host Ids Example 來自 What is a Sub? (1) Sub 1 Sub 2 Main Network A sub is a subsection of an work, defined for administrative purpose or to cut down on broadcast traffic, as all messages on a work are “heard” by all hosts whether the message is for that host or not. Message sent from one host to another within the same sub do not need to be routed, but messages sent between hosts in different subs must be routed. Subs are connected by routers, or default gateways. 來自 What is a Sub? (2) Network ID Host ID 1 0 Example Network ID FROM ISP No. of Network = 1 SUBNET MASK No. of Hosts = 65534 (2^162) Network ID Host ID 1 0 We need more works Sub ID Borrow from Host ID 來自 What is a Sub? (3) After Sub Network ID bee Sub mask bee No. of Subs 254 Host for per Sub 254 (2^82) Network ID Host ID 1 0 Sub ID Use all 8 bit 11111111 for Sub 254 binations (2^82)* Only 8 bit for Host * However, according to RFC 1812, 255 binations can be achieved. 來自 What is a Sub? (4) After Sub Network ID Sub Mask Host Range ………… …………. TOTAL 254 SUBNETS 254 HOSTS PER SUBNET 來自 Why Subting? ? Reduced work traffic – ? smaller the work smaller the broadcast domains and less work traffic on that work segment ? Optimized work performance – ? result of reduced work traffic ? Simplified management – ? easier to identify and isolate work problems in a smaller group ? Facilitated spanning of large geographical distances – ? since WAN links are considerably slower and more expensive。 a message sent to this address is broadcast to each machine on the sub. ? – send to “all nodes” on work ? Limited Broadcast ? Network ID and/or Host ID Cannot Be All Bits Set to 0 ? used by Cisco routers to designate the default route ? 0 means “this work or segment”, or “this node” ? Host ID Must Be Unique to the Network 來自 Assigning Network Addresses Router 1 2 3 Router 來自 Assigning Host Addresses Router Router 1 2 3 來自 Subting What is a Sub? Why Subting? Implementing Subting Sub Masks Default Sub Masks Possible Sub Masks for Class A, B a
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