Product specifications

Chapter 2: Product Overview Efficient Networks
®
Router family
Technical Reference Guide
Page 2-6 Efficient Networks
®
Bridging has these capabilities:
• Allows protocols that cannot be routed (such as NETBIOS) to be forwarded.
• Allows optimizing internetwork capacity by localizing traffic on LAN
segments.
• Extends the physical reach of networks beyond the limits of each LAN
segment.
• Bridge filtering may increase network security.
Our bridging support includes the IEEE 802.1D standard for LAN-to-LAN bridging and
the Spanning Tree Protocol for interoperability with other vendors’ bridge/routers.
Bridging is provided over PPP as well as adjacent LAN ports.
Bridge-Only Units
A series of bridge-only units is available, both upgradable and non-upgradable. An
upgradable bridge can be upgraded to a router; a non-upgradable bridge cannot.
These bridge-only units are pre-configured; no further configuration is required. The
unit comes up in bridge mode automatically.
Upgrading an upgradable bridge to become a router requires the addition of a
software option key. The software option key turns on the IP Routing feature.
Bridge Filtering
You can control the flow of packets through the router using bridge filters. The filters
can “deny” or “allow” packets to cross the network based on the content of the
packets. This feature lets you restrict or forward messages with a specified address,
protocol, or data content. Common uses are to prevent access to remote networks,
control unauthorized access to the local network, and limit unnecessary traffic.
For example, to restrict remote access for specific users, you could define bridge
filters using the local MAC address of each user to be restricted. Each bridge filter is
specified as a “deny” filter based on the MAC address and position of the address
within the packet. Deny filtering mode is then enabled to initiate bridge filtering. While
in deny mode, all packets containing one of the filtered MAC addresses are denied
bridging across the router.
Similarly, protocol filtering can be used to prevent a specific protocol from being
bridged. In this case, the protocol ID field in a packet is used to deny or allow a
packet. You can also restrict the bridging of specific broadcast packets.
For a further discussion of bridge filtering, see “Bridge Filtering” on page 5-75.