D-Link DGS-3224TGR - Switch, Руководство пользователя

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DGS-3224TGR Gigabit Ethernet Switch User’s Guide
25
MAC-Based Network Access Control
802.1X
Client
Network access controlled port
Network access uncontrolled port
RADIUS
Server
Ethernet Switch
802.1X
Client
802.1X
Client
802.1X
Client
802.1X
Client
802.1X
Client
802.1X
Client
802.1X
Client
802.1X
Client
802.1X
Client
802.1X
Client
802.1X
Client
…
Figure 5- 11. Example of Typical MAC-Based Configuration
In order to successfully make use of 802.1x in a shared media LAN segment, it would be necessary to create “virtual” Ports,
one for each attached device that required access to the LAN. The Switch would regard the single physical Port connecting
it to the shared media segment as consisting of a number of distinct virtual Ports, each virtual Port being independently
controlled from the point of view of EAPOL exchanges and authorization state. The Switch learns each attached device’s
individual MAC address, and effectively creates a virtual Port that the attached device can then use to communicate with
the LAN via the Switch.
DHCP
The Dynamic Host Configuration Protocol (DHCP) can reduce the administrative burden of assigning and maintaining IP
address information. DHCP provides reliable and simple TCP/IP network configuration, ensures that address conflicts do
not occur, and helps to conserve the use of IP addresses through the centralized management of address allocation.
Dynamic address allocation enables a client to be assigned an IP address from a pool of free addresses. Each address is
assigned with a lease and a lease expiration period. The client must renew the lease to continue using the assigned address.
Dynamically assigned addresses can be returned to the free address pool if the computer is not being used, if it is moved to
another subnet, of if its lease expires. Usually, network policy ensures that the same IP address is assigned to a client each
time and that addresses returned to the free address pool are reassigned.
When the address lease expires, the DHCP client enters the renewing state. The client sends a request message to the DHCP
server that provided the address. The DHCP server sends an acknowledgement that contains the new lease and
configuration parameters. The client then updates its configuration values and returns to the bound state.