Bridging

For data that is restricted to the Token Ring networks available from the SR-TB bridgeÕs front panel, the bridging method used is user-conÞgurable via local management to be Source Route-only (bridged packets must include RIF information and will be source routed; no transparent bridging is enabled), Source Route-Transparent (bridging method will be determined by whether the RII bit is set), or Transparent only (no source routed packets will be bridged). Remote management of these interfaces is based upon their current mode (as set through local management).

For data that will ultimately be sent across an FDDI interface to an ATM, Ethernet, FDDI, or another Token Ring segment, the Routing Information Field will be stripped from the packet so the packet can be transparently bridged onto Ethernet or FDDI media; however, the RIF information as well as the source address of the packet is stored in a RIF cache of the SR-TB bridge. When data is returned to that source address, the SR-TB bridge can look up the address information in its RIF cache, append the proper Routing Information onto the packet, and then forward the data to the Token Ring segment.

The RIF cache is a software table that can store up to 8192 entries. An SR-TB bridge updates its RIF cache much like a Transparent bridge dynamically updates its Filtering Database: it learns new address information by listening to incoming packets on each port, saves that information to an Address Database, andÑif the address was learned to be Source-Route capableÑupdates routing information for that source address in the RIF cache. Every time a packet arrives from an FDDI interface for a MAC address that is communicating through the SR-TB bridgeÕs front panel, the RIF cache table is searched for an address/RIF match.

There are conÞguration issues when a Token Ring module receives a packet from an FDDI interface for a destination address that is unknown, and not in its Address Database or RIF cache. You must conÞgure your SR-TB bridge to treat incoming packets with an unknown destination address as either a Source Route or Transparently bridged packet (since Token Ring end stations attached to the module may or may not support Source Routing).

If the bridge is conÞgured to treat an incoming packet with unknown addresses as a Source Routed frame, it will forward it using either STE or ARE frames. If the bridge is conÞgured to treat an incoming packet with an unknown destination as a Transparently bridged frame, it simply forwards the frame.

After a packet with a previously unknown destination has been bridged successfully, and communication begins between the two end nodes, the RIF cache will be updated and packets will be translated as described previously.

Bridging Basics

4-5

Page 50 Page 52
Page 51
Image 51
Cabletron Systems CSX200, CSX400 manual Bridging
Page 50 Page 52

CSX200, CSX400 specifications

Cabletron Systems was a leading developer of networking solutions, and its CSX400 and CSX200 series of high-performance switches represent some of the key innovations in the field of enterprise networking during their time. Both models were geared towards enhancing network reliability, efficiency, and speed, particularly in environments where heavy data traffic and complex networking demands were prevalent.

The CSX400, designed for larger enterprises, boasts a robust architecture capable of handling significant throughput. One of its standout features is its stackable design, allowing multiple switches to be interconnected and managed seamlessly as a single unit. This scalability provides organizations with the flexibility to expand their networks without significant infrastructure overhauls. The CSX400 supports various Ethernet standards, including 10/100 Ethernet and Gigabit Ethernet, positioning it to effectively manage both legacy and modern networking requirements.

In addition to its scalability, the CSX400 is distinguished by its advanced Layer 2 and Layer 3 routing capabilities. This dual-layer functionality enables efficient data handling and is instrumental in managing traffic between different network segments. Moreover, the switch incorporates features like VLAN (Virtual Local Area Network) support and Quality of Service (QoS) prioritization, allowing for enhanced performance of critical applications and streamlined bandwidth allocation.

On the other hand, the CSX200 series is tailored for smaller enterprises or branch offices needing a reliable yet efficient networking solution. Despite its compact design, the CSX200 is equipped with essential features that promote effective network management and security. It offers a simplified management interface, making it user-friendly for network administrators. The switch also provides essential access control measures, employing technologies like IEEE 802.1X for network access security.

Both the CSX400 and CSX200 prioritize performance through the incorporation of advanced switching technologies. They support features such as Spanning Tree Protocol (STP), enabling loop-free topologies and enhanced network resilience. These attributes are particularly crucial in dynamic networking environments where downtime can have significant repercussions on business operations.

Overall, Cabletron Systems' CSX400 and CSX200 series represent a blend of scalability, advanced routing capabilities, and user-friendly management, making them vital assets for organizations looking to optimize their network infrastructure during a period of rapid technological evolution. With their rich feature sets and unwavering performance, these switches helped pave the way for modern networking solutions that cater to diverse enterprise needs.
Top Page Image Contents