Configure Bridging of Routed Protocols

Source-route bridges use Media Access Control (MAC) information, specifically the information contained in the RIF, to bridge packets. A RIF contains a series of ring and bridge numbers that represent the possible paths the source node might use to send packets to the destination. Each ring number in the RIF represents a single Token Ring in the source-route bridged network and is designated by a unique 12-bit ring number. Each bridge number represents a bridge that is between two Token Rings in the SRB network and is designated by a unique 4-bit bridge number. The information in a RIF is derived from explorer packets traversing the source-route bridged network. Without the RIF information, a packet could not be bridged across a source-route bridged network.

Unlike source-route bridges, Level 3 routers use protocol-specific information (for example, Novell Internetwork Packet Exchange (IPX) or Xerox Network Systems (XNS) headers) rather than MAC information to route datagrams. As a result, the Cisco IOS software default for routed protocols is to not collect RIF information and to not be able to bridge routed protocols. However, if you want the software to bridge routed protocols across a source-route bridged network, the software must be able to collect and use RIF information to bridge packets across a source-route bridged network. You can configure the software to append RIF information to routed protocols so that routed protocols can be bridged. Figure 49 shows a network topology in which you would want to use this feature.

Figure 49 Topology for Bridging Routed Protocols across a Source-Route Bridged

Network

Cisco routed network

Source-route bridged

Token Ring network

S2328

To configure the Cisco IOS software to bridge routed protocols, you must perform the task in the first section, and optionally, one or both of the tasks in the other sections as follows:

•

Enable Use of the RIF

Configure a Static RIF Entry

Configure the RIF Timeout Interval

Enable Use of the RIF

You can configure the Cisco IOS software so that it will append RIF information to the routed protocols. This allows routed protocols to be bridged across a source-route bridged network. The routed protocols that you can bridge are as follows:

•

Apollo Domain

AppleTalk

ISO Connectionless Network Service (CLNS)

DECnet

IPX

Configuring Source-Route Bridging BC-117

Cisco Systems BC-109 manual Configure Bridging of Routed Protocols, Enable Use of the RIF

Models: BC-109