Cabletron Systems HSIM-W6 Guía de instalación descargar pdf (Pagina 23)

HSIM-W84 Firmware Support

HSIM-W84 Installation Guide 2-11

Bridging and Routing

Bridging — Bridging connects two or more separate networks together. The bridge examines a

portion of each network frame called the header. This header contains control information for the

frame. The bridge compares the destination address of the frame to a table of source addresses

(bridges dynamically learn the physical location of devices by logging the source addresses of

each frame and the bridge port the frame was received on in the source address table). In

transparent bridging, the decision to forward the frame is based on this comparison. If the address

indicates that the sending station and the destination station are on the same side of the bridge, the

frame is not forwarded across the bridge. If the addresses do not indicate that, the bridge forwards

the broadcast frame across the bridge to the other network(s).

Bridging allows frames to be sent to all destinations regardless of the network protocols used. It

also allows protocols that cannot be routed (such as NETBIOS) to be forwarded, and optimizes

internetwork capacity by localizing trafﬁc on LAN segments. A bridge extends the physical reach

of networks beyond the limits of each LAN segment. Filters can be used to increase network

security in bridged networks, and restrict message forwarding by using user-built address

tables (non-transparent bridging).

Routing — Routing provides a way to transfer user data from source to destination over different

LAN and WAN links using one or more network protocol formats. Routing relies on routing

address tables to determine the best path for each packet. Routing tables can be seeded (i.e.,

addresses for remote destinations are placed in the table along with network address masks and a

metric for path latency). Routing tables are also built dynamically (i.e., the location of remote

stations, hosts and networks are updated through inter-router protocols). Routing helps to increase

network capacity by localizing trafﬁc on LAN segments and broadcasts that would result from

bridged trafﬁc. It also provides security by isolating trafﬁc on segmented LANs. Routing extends

the world-wide reach of networks.

HSIM-W84 Bridging and Routing — The HSIM-W84 can operate as a bridge, a router, or both.

The HSIM-W84 operates as a router for network protocols that are supported when routing is

enabled and operates as a bridge when bridging is enabled. When both bridging and routing are

enabled, routing takes precedence over bridging (i.e., the HSIM-W84 uses the protocol address

information of the packet to route the packet to the correct destination, and if the protocol is not

supported, the device uses the MAC address information to bridge the packet).

Operation of the HSIM-W84 is inﬂuenced by routing and bridging controls and ﬁlters set during

HSIM-W84 conﬁguration. General IP routing, and routing or bridging from speciﬁc remote

routers are controls set during the conﬁguration process.

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Cabletron Systems HSIM-W6 Guía de instalación Pagina 23