>> In story number two, host A, the source, once again performs the boolean and operationto determine that its network ID is 10.10.1.0.
>>在故事2中，主机A，源，再次执行布尔和运算来确定它的网络ID是10.10.1.0。
This time, the destination IP address is 10.10.4.1, host X.
这一次，目的IP地址是10.10.4.1，主机X。
Using the source maskof 255.255.255.0, the second boolean and operation resultsin a destination network ID of 10.10.4.0.
使用源掩码255.255.255.0，第二个布尔值和操作的结果是目标网络ID为10.10.4.0。
The two network IDs are not the same,and the source realizes it can't send traffic directly to the destination.
这两个网络id不相同，源意识到它不能将流量直接发送到目的地。
One of the golden rules of networking is that direct communication is only possiblebetween devices on the same network.
联网的黄金法则之一是，直接通信只能在同一网络上的设备之间进行。
The source needs to get the traffic now to its default gateway,an interface on a router connected to its network.
源现在需要将流量传输到其默认网关，即连接到其网络的路由器上的接口。
When a device is configured either statically or dynamically, in addition to an IP addressand a subnet mask, that device also gets an IP address of a router interface on the network.
当设备被静态或动态配置时，除了IP地址和子网掩码之外，该设备还会获得网络上路由器接口的IP地址。
That router interface is responsible for taking traffic off the network destinedfor other networks and bringing traffic from other networks back onto the network.
该路由器接口负责从发送到其他网络的网络中提取流量，并将来自其他网络的流量带回网络中。
We call that interface on the router performing those functions a default gateway.
我们将路由器上执行这些功能的接口称为默认网关。
And its IP address needs to be known by hosts on the network.
它的IP地址需要被网络上的主机知道。
Routers are the devices that connect different networks together.
路由器是连接不同网络的设备。
And each interface of a router connects to a different network.
路由器的每个接口都连接到不同的网络。
Even though host A, the source, determines that the traffic is remote,it will once again send an ARP request, which is broadcasted to all devices on its network.
即使源主机A确定流量是远程的，它也将再次发送ARP请求，该请求将广播到其网络上的所有设备。
This time, the ARP request is looking for the MAC address of host A's default gateway.
这一次，ARP请求查找主机A的默认网关的MAC地址。
In our story, we'll say the gateways IP address is 10.10.1.99.
在我们的故事中，我们将说网关IP地址是10.10.1.99。
The gateway will send its MAC address in a unicast ARP reply backto host A.
网关将以单播ARP应答的方式将其MAC地址发送回主机a。
Host A now sends the traffic with a destination MAC address of the routerand the destination IP address of the actual destination,which could be two, five, ten or more routers away.
主机A现在用路由器的目标MAC地址和实际目标的目标IP地址发送流量，实际目标可能是两个、五个、十个或更多路由器。
Incidentally, routers never forward broadcasts to other networks.
顺便说一句，路由器从不转发广播到其他网络。
Router interfaces will hear broadcasts on the networks they're connected tobut will never forward broadcast traffic from one networkout of another interface to a different network.
路由器接口将听到它们所连接的网络上的广播，但决不会将广播流量从一个网络转发到另一个接口到另一个网络。
If they did that, a simple broadcast could go around the world and back.
如果他们这样做了，一个简单的广播就可以在世界各地来回播放。
Just to understand our typology, a map or diagram of the network,you'll notice that each interconnection between router interfaces,including the router interfaces themselves, is considered a separate network.
为了理解我们的类型，一个网络的地图或图表，您会注意到路由器接口之间的每个互连，包括路由器接口本身，都被认为是一个单独的网络。
That means every device between router A's right interface and router B's left interface,including those interfaces, is on that shared network.
这意味着路由器A的右接口和路由器B的左接口之间的每个设备，包括那些接口，都在那个共享网络上。
The network identifier would be 10.10.2.0 if the subnet mask was 255.255.255.0.
如果子网掩码是255.255.255.0，则网络标识符为10.10.2.0。
And all devices on that network would need an IP address starting off with 10.10.2.
网络上的所有设备都需要一个IP地址以10.10.2开头。
The last octet would be the host octet.
最后的八位字节将是本地主机八位位组。
Following the IP addressing rules we've discussed,every device on a share network starts off with the same network identifier.
按照我们讨论的IP寻址规则，共享网络上的每个设备都以相同的网络标识符开始。
In this story, we'll just make it easy and make the subnet mask for all devicesand networks 255.255.255.0, which means all hostson each network will share the same first three numbers or octets.
在本例中，我们将简化并为所有设备和网络创建子网掩码255.255.255.0，这意味着每个网络上的所有主机将共享相同的前三个数字或八进制数。
The last octet will be a host identifier for all networks.
最后的八位字节将是所有网络的主机标识符。
Everything between router B's right interface and router C's left interface is a network.
路由器B的右接口和路由器C的左接口之间的所有东西都是一个网络。
That network identifier is 10.10.3.0.
网络标识符是10.10.3.0。
Our last network in this topology is everything to the rightof router C's right interface, the 10.10.4.0 network.
这个拓扑中的最后一个网络是路由器C的正确接口10.10.4.0网络右边的所有东西。
转载于:https://www.cnblogs.com/sec875/articles/10344646.html
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