5-3 Routing :
Within a network or a subnetwork, hosts communicate with each other without the need for any Network layer intermediary device. When a host needs to communicate with another network, an intermediary device, or router, acts as a gateway to the other network.
As a part of its configuration, a host has a default gateway address defined. As shown in the figure, this gateway address is the address of a router interface that is connected to the same network as the host.
Keep in mind that it is not feasible for a particular host to know the address of every device on the Internet with which it may have to communicate. To communicate with a device on another network, a host uses the address of this gateway, or default gateway, to forward a packet outside the local network. The router also needs a route that defines where to forward the packet next. This is called the next-hop address. If a route is available to the router, the router will forward the packet to the next-hop router that offers a path to the destination network.
If communication is between hosts in different networks, the local network delivers the packet from the source to its gateway router. The router examines the network portion of the packet destination address and forwards the packet to the appropriate interface. If the destination network is directly connected to this router, the packet is forwarded directly to that host. If the destination network is not directly connected, the packet is forwarded on to a second router that is the next-hop router.
5-4-1 Default Gateway
The default gateway is configured on a host. On a Windows computer, the Internet Protocol (TCP/IP) Properties tools are used to enter the default gateway IPv4 address. Both the host IPv4 address and the gateway address must have the same network (and subnet, if used) portion of their respective addresses. Default gateway always is the last host possible address .
5-4 IP Address Types :
1-Private Addresses :
Although most IPv4 host addresses are public addresses designated for use in networks that are accessible on the Internet, there are blocks of addresses that are used in networks that require limited or no Internet access. These addresses are called private addresses.
The private address blocks are:
10.0.0.0 to 10.255.255.255 (10.0.0.0 /8)
172.16.0.0 to 172.31.255.255 (172.16.0.0 /12)
192.168.0.0 to 192.168.255.255 (192.168.0.0 /16)
2-Public Addresses
The vast majority of the addresses in the IPv4 unicast host range are public addresses. These addresses are designed to be used in the hosts that are publicly accessible from the Internet. Even within these address blocks, there are many addresses that are designated for other special purposes.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .