Cabletron Systems CyberSWITCH CSX400, Руководство пользователя

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About the CSX400
CSX400 and CSX400-DC User’s Guide 11
HDLC
Cabletron Systems has provided the High-level Data Link Control (HDLC) protocol which is used
in conjunction with the Inverse Multiplexing (IMUX) feature and the WPIM-HDSL to conserve a
user’s WAN bandwidth between two Cabletron Systems products, over a point-to-point
connection. Cabletron Systems products such as the CSX400, CSX200, and HSIM-W6 must be in
use on both ends of the WAN link for these functions to work. The HDLC (RAW) protocol reduces
the amount of overhead information that needs to be contained within each data packet to direct it
to its destination. This decreased packet overhead provides the IMUX and HDSL functions with
more bandwidth to transfer user data.
DHCP and NAT
The Dynamic Host Configuration Protocol (DHCP) and Network Address Translation (NAT)
method eliminates the expense of purchasing limited public IP addresses for each client on a local
network, and the need to re-configure a client if it is moved to a different network.
The CSX400 acts as a DHCP server that allows individual clients (PCs, network equipment) to
take turns using a range of private IP addresses (often referred to as local IP addresses), and
provides optional secondary setup features for these clients on a per-port basis. The CSX400
distributes these addresses dynamically assigning a local IP address to an individual client from a
range of 253 available addresses in its table on a first-come-first-served basis. This local IP address
is then “leased” for a predetermined amount of time, which is configured for the particular port.
Each Ethernet port provides DHCP services for one Class C subnet and secondary setup features
for individual clients that support the use of a default gateway, domain name and WINs server.
On the Wide Area Network (WAN) side, the Network Address Translation (NAT) routing method
is used to enable clients assigned with local IP addresses to use the public IP address(es) of the
CSX400 WAN interface(s) to access the WAN.
NOTE
A private or “local” network is referred to as a sub network that is using private or
“local” IP addresses. An “outside” network refers to a Wide Area Network (WAN)
commonly known as an Internet, an intranet is an “Internet” in use on a facility or
campus where registered public IP addresses are required.