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Cisco IOS Bridging and IBM Networking Configuration Guide, Release 12.1
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About the Cisco IOS Software Documentation
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Using Cisco IOS Software
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Overview of SNA Internetworking
- Part 1: Bridging
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Part 2: IBM Networking
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Overview of IBM Networking
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Configuring Remote Source-Route Bridging
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Configuring Data-Link Switching Plus
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Configuring Serial Tunnel and Block Serial Tunnel
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Configuring LLC2 and SDLC Parameters
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Configuring IBM Network Media Translation
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Configuring Frame Relay Access Support
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Configuring NCIA Server
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Configuring the Airline Product Set
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Configuring DSPU and SNA Service Point Support
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Configuring SNA Switching Services
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Configuring Cisco Transaction Connection
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Configuring Cisco Mainframe Channel Connection Adapters
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Configuring CLAW and TCP/IP Offload Support
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Configuring CMPC and CSNA
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Configuring CMPC+
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Configuring the TN3270 Server
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Index
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Table Of Contents
Configuring Source-Route Bridging
Configuring Source-Route Bridging
Configuring a Dual-Port Bridge
Configuring a Multiport Bridge Using a Virtual Ring
Configuring Fast-Switching SRB over FDDI
Configuring SRB over Frame Relay
Enabling the Forwarding and Blocking of Spanning-Tree Explorers
Enabling the Automatic Spanning-Tree Function
Configuring Bridging of Routed Protocols
Configuring a Static RIF Entry
Configuring the RIF Timeout Interval
Configuring Translation between SRB and Transparent Bridging Environments
Enabling Bridging between Transparent Bridging and SRB
Disabling Fast-Switched SR/TLB
Enabling Translation Compatibility with IBM 8209 Bridges
Enabling Token Ring LLC2-to-Ethernet Conversion
Enabling the Proxy Explorers Feature on the Appropriate Interface
Specifying Timeout and Enabling NetBIOS Name Caching
Configuring the NetBIOS Cache Name Length
Creating Static Entries in the NetBIOS Name Cache
Specifying Dead-Time Intervals for NetBIOS Packets
Configuring LNM Software on the Management Stations to Communicate with the Router
Disabling Automatic Report Path Trace Function
Preventing LNM Stations from Modifying Cisco IOS Software Parameters
Enabling Other LRMs to Change Router Parameters
Applying a Password to an LNM Reporting Link
Changing an LNM Reporting Interval
Enabling the RPS Express Buffer Function
Configuring NetBIOS Access Filters
Configuring Administrative Filters for Token Ring Traffic
Configuring Access Expressions that Combine Administrative Filters
Enabling or Disabling the Source-Route Fast-Switching Cache
Enabling or Disabling the Source-Route Autonomous-Switching Cache
Establishing the Connection Timeout Interval
Optimizing Explorer Processing
Establishing SRB Interoperability with Specific Token Ring Implementations
Establishing SRB Interoperability with TI MAC Firmware
Reporting Spurious Frame-Copied Errors
Monitoring and Maintaining the SRB Network
Basic SRB with Spanning-Tree Explorers Example
SRB with Automatic Spanning-Tree Function Configuration Example
Optimized Explorer Processing Configuration Example
SRB and Routing Certain Protocols Example
SRB with Multiple Virtual Ring Groups Example
SRB over FDDI Configuration Examples
SRB over FDDI Fast-Switching Example
SRB over Frame Relay Configuration Example
Adding a Static RIF Cache Entry Example
Adding a Static RIF Cache Entry for a Two-Hop Path Example
SR/TLB for a Simple Network Example
SR/TLB with Access Filtering Example
NetBIOS Support with a Static NetBIOS Cache Entry Example
LNM for a Simple Network Example
LNM for a More Complex Network Example
NetBIOS Access Filters Example
Filtering Bridged Token Ring Packets to IBM Machines Example
Administrative Access Filters—Filtering SNAP Frames on Output Example
Creating Access Filters Example
Back-to-Back Routers ATM Configuration Example
Single ATM PVC and Single Virtual Ring Per Router Configuration Example
Multiple ATM PVCs and Multiple Virtual Rings on One Router Configuration Example
Multiple ATM PVCs with a Single Virtual Ring on the Router Configuration Example
Configuring Source-Route Bridging
This chapter describes source-route bridging (SRB) configuration tasks. For a discussion of remote source-route bridging (RSRB) configuration tasks, refer to the "Configuring Remote Source-Route Bridging" chapter in this publication.
For a complete description of the SRB commands mentioned in this chapter, refer to the "Source-Route Bridging Commands" chapter in the Cisco IOS Bridging and IBM Networking Command Reference, Volume I. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.
This chapter contains the following sections:
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Monitoring and Maintaining the SRB Network
Technology Overview
Cisco's IOS bridging software includes SRB capability. A source-route bridge connects multiple physical Token Rings into one logical network segment. If the network segment bridges only Token Ring media to provide connectivity, the technology is termed SRB. If the network bridges Token Ring and non-Token Ring media is introduced into the bridged network segment, the technology is termed RSRB.
SRB enables routers to simultaneously act as a Level 3 router and a Level 2 source-route bridge. Thus, protocols such as Novell's IPX or XNS can be routed on Token Rings, while other protocols such as Systems Network Architecture (SNA) or NetBIOS are source-route bridged.
SRB technology is a combination of bridging and routing functions. A source-route bridge can make routing decisions based on the contents of the MAC frame header. Keeping the routing function at the MAC, or Level 2, layer allows the higher-layer protocols to execute their tasks more efficiently and allows the LAN to be expanded without the knowledge of the higher-layer protocols.
As designed by IBM and the IEEE 802.5 committee, source-route bridges connect extended Token Ring LANs. A source-route bridge uses the RIF in the IEEE 802.5 MAC header of a datagram (Figure 22) to determine which rings or Token Ring network segments the packet must transit.
Figure 22 IEEE 802.5 Token Ring Frame Format
The source station inserts the RIF into the MAC header immediately following the source address field in every frame, giving this style of bridging its name. The destination station reverses the routing field to reach the originating station.
The information in a RIF is derived from explorer packets generated by the source node. These explorer packets traverse the entire source-route bridge network, gathering information on the possible paths the source node might use to send packets to the destination.
Transparent spanning-tree bridging requires time to recompute a topology in the event of a failure; SRB, which maintains multiple paths, allows fast selection of alternate routes in the event of failure. Most importantly, SRB allows the end stations to determine the routes the frames take.
SRB Features
Cisco's SRB implementation has the following features:
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SRB Configuration Task List
Perform the tasks in the following sections to configure SRB:
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Caution
Configuring Source-Route Bridging
Our implementation of source-route bridging enables you to connect two or more Token Ring networks using either Token Ring or Fiber Distributed Data Interface (FDDI) media.
The Cisco IOS software offers the ability to encapsulate source-route bridging traffic using RFC 1490 Bridged 802.5 encapsulation. This encapsulation provides SRB over Frame Relay functionality.
You can configure the Cisco IOS software for source-route bridging by performing the tasks in one of the first three sections and, optionally, the tasks in the last section:
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Configuring a Dual-Port Bridge
A dual-port bridge is the simplest source-route bridging configuration. When configured as a dual-port bridge, the access server or router serves to connect two Token Ring LANs. One LAN is connected through one port (Token Ring interface), and the other LAN is connected through the other port (also a Token Ring interface). Figure 23 shows a dual-port bridge.
Figure 23 Dual-Port Bridge
To configure a dual-port bridge that connects two Token Rings, you must enable source-route bridging on each of the Token Ring interfaces that connect to the two Token Rings. To enable source-route bridging, use the following command in interface configuration mode for each of the Token Ring interfaces:
source-bridge local-ring bridge-number target-ring
Enables local source-route bridging on a Token Ring interface.
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A dual-port bridge is a limitation imposed by IBM Token Ring chips; the chips can process only two ring numbers. If you have a router with two or more Token Ring interfaces, you can work around the two-ring number limitation. You can configure your router as multiple dual-port bridges or as a multiport bridge using a virtual ring.
You can define several separate dual-port bridges in the same router. However, the routers on the LANs cannot have any-to-any connectivity; that is, they cannot connect to every other router on the bridged LANs. Only the routers connected to the dual-port bridge can communicate with one another. Figure 24 shows two separate dual-port bridges (T0-T2 and T1-T3) configured on the same router.
Figure 24 Multiple Dual-Port Bridges
To configure multiple dual-port source-route bridges, use the following command in interface configuration mode for each Token Ring interface that is part of a dual-port bridge:
source-bridge local-ring bridge-number target-ring
Enables local source-route bridging on a Token Ring interface.
If you want your network to use only SRB, you can connect as many routers as you need via Token Rings. Remember, source-route bridging requires you to bridge only Token Ring media.
Configuring a Multiport Bridge Using a Virtual Ring
A better solution for overcoming the two-ring number limitation of IBM Token Ring chips is to configure a multiport bridge using a virtual ring. A virtual ring on a multiport bridge allows the router to interconnect three or more LANs with any-to-any connectivity; that is, connectivity between any of the routers on each of the three LANs is allowed. A virtual ring creates a logical Token Ring internal to the Cisco IOS software, which causes all the Token Rings connected to the router to be treated as if they are all on the same Token Ring. The virtual ring is called a ring group. Figure 25 shows a multiport bridge using a virtual ring.
Figure 25 Multiport Bridge Using a Virtual Ring
To take advantage of this virtual ring feature, each Token Ring interface on the router must be configured to belong to the same ring group. For information about configuring a multiport bridge using a virtual ring, see the "Configuring a Multiport Bridge Using a Virtual Ring" section later in this chapter.
To configure a source-route bridge to have more than two network interfaces, you must perform the following tasks:
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Once you have completed these tasks, the router acts as a multiport bridge, not as a dual-port bridge.
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Defining a Ring Group in SRB Context
Because all IBM Token Ring chips can process only two ring numbers, we have implemented the concept of a ring group or virtual ring. A ring group is a collection of Token Ring interfaces in one or more routers that share the same ring number. This ring number is used just like a physical ring number, showing up in any route descriptors contained in packets being bridged. Within the context of a multiport bridge that uses SRB rather than RSRB, the ring group resides in the same router. See the "Configuring Remote Source-Route Bridging" chapter to compare ring groups in the SRB and RSRB context.
A ring group must be assigned a ring number that is unique throughout the network. It is possible to assign different Token Ring interfaces on the same router to different ring groups, if, for example, you plan to administer them as interfaces in separate domains.
To define or remove a ring group, use one of the following commands in global configuration mode:
source-bridge ring-group ring-group [virtual-mac-address]
Defines a ring group.
no source-bridge ring-group ring-group [virtual-mac-address]
Removes a ring group.
Enabling SRB and Assigning a Ring Group to an Interface
After you have defined a ring group, you must assign that ring group to those interfaces you plan to include in that ring group. An interface can only be assigned to one ring group. To enable any-to-any connectivity among the end stations connected through this multiport bridge, you must assign the same target ring number to all Token Ring interfaces on the router.
To enable SRB and assign a ring group to an interface, use the following command in interface configuration mode:
source-bridge local-ring bridge-number target-ring
Enables source-route bridging and assigns a ring group to a Token Ring interface.
Configuring SRB over FDDI
Cisco's implementation of SRB expands the basic functionality to allow autonomous switching of SRB network traffic for FDDI interfaces, adding counters to SRB accounting statistics, and implementing process-level switching of SRB over FDDI. This functionality provides a significant increase in performance for Token Rings interconnected across an FDDI backbone (Figure 26).
SRB over FDDI is supported on the Cisco 4000-M, Cisco 4500-M, Cisco 4700-M, Cisco 7000 series, Cisco 7200 series, and Cisco 7500 routers.
Figure 26 Autonomous FDDI SRB
To configure autonomous FDDI SRB, use the following commands, beginning in global configuration mode:
Configuring Fast-Switching SRB over FDDI
Fast-Switching SRB over FDDI enhances performance. For example, if you want to use access-lists, fast-switching SRB over FDDI provides fast performance and access-list filters capability.
To configure fast-switching SRB over FDDI, use the following commands, beginning in global configuration mode:
Configuring SRB over Frame Relay
Cisco IOS software offers the ability to encapsulate SRB traffic using RFC 1490 Bridged 802.5 encapsulation. This provides SRB over Frame Relay functionality that is interoperable with other vendors' implementations of SRB over Frame Relay and with some vendors' implementations of FRAS BAN.
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To configure SRB over Frame Relay, use the following commands in interface configuration mode:
Enabling the Forwarding and Blocking of Spanning-Tree Explorers
When trying to determine the location of remote destinations on a source-route bridge, the source device will need to send explorer packets. Explorer packets are used to collect routing information field (RIF) information. The source device can send spanning-tree explorers or all-routes explorers. Note that some older IBM devices generate only all-routes explorer packets, but many newer IBM devices are capable of generating spanning-tree explorer packets.
A spanning-tree explorer packet is an explorer packet that is sent to a defined group of nodes that comprise a statically configured spanning tree in the network. In contrast, an all-routes explorer packet is an explorer packet that is sent to every node in the network on every path.
Forwarding all-routes explorer packets is the default. However, in complicated source-route bridging topologies, using this default can generate an exponentially large number of explorers that are traversing the network. The number of explorer packets becomes quite large because duplicate explorer packets are sent across the network to every node on every path. Eventually each explorer packet will reach the destination device. The destination device will respond to each of these explorer packets. It is from these responses that the source device will collect the RIF and determine which route it will use to communicate with the destination device. Usually, the route contained in the first returned response will be used.
The number of explorer packets traversing the network can be reduced by sending spanning-tree explorer packets. Spanning-tree explorer packets are sent to specific nodes; that is, to only the nodes on the spanning tree, not to all nodes in the network. You must manually configure the spanning-tree topology over which the spanning-tree explorers are sent. You do this by configuring which interfaces on the routers will forward spanning-tree explorers and which interfaces will block them.
To enable forwarding of spanning-tree explorers on an outgoing interface, use the following command in interface configuration mode:
source-bridge spanning
Enables the forwarding of spanning-tree explorer packets on an interface.
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To block forwarding of spanning tree explorers on an outgoing interface, use the following command in interface configuration mode:
Enabling the Automatic Spanning-Tree Function
The automatic spanning-tree function supports automatic resolution of spanning trees in SRB networks, which provides a single path for spanning explorer frames to traverse from a given node in the network to another. Spanning explorer frames have a single-route broadcast indicator set in the routing information field. Port identifiers consist of ring numbers and bridge numbers associated with the ports. The spanning-tree algorithm for SRB does not support Topology Change Notification bridge protocol data unit (BDPU).
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To create a bridge group that runs an automatic spanning-tree function compatible with the IBM SRB spanning-tree implementation, use the following command in global configuration mode:
bridge bridge-group protocol ibm
Creates a bridge group that runs the automatic spanning-tree function.
To enable the automatic spanning-tree function for a specified group of bridged interfaces, use the following command in interface configuration mode:
source-bridge spanning bridge-group
Enables the automatic spanning-tree function on a group of bridged interfaces.
To assign a path cost for a specified interface, use the following command in interface configuration mode:
source-bridge spanning bridge-group path-cost path-cost
Assigns a path cost for a specified group of bridged interfaces.
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See the end of this chapter for an example of source-route bridging with the automatic spanning-tree function enabled.
Limiting the Maximum SRB Hops
You can minimize explorer storms if you limit the maximum number of source-route bridge hops. For example, if the largest number of hops in the best route between two end stations is six, it might be appropriate to limit the maximum source-route bridging hops to six to eliminate unnecessary traffic. This setting affects spanning-tree explorers and all-routes explorers sent from source devices.
To limit the number of SRB hops, use one of the following commands in interface configuration mode:
Configuring 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 27 shows a network topology in which you would want to use this feature.
Figure 27 Topology for Bridging Routed Protocols across a Source-Route Bridged Network
To configure the Cisco IOS software to bridge routed protocols, perform the following tasks:
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Enabling 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:
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Enable use of the RIF only on Token Ring interfaces on the router.
To configure the Cisco IOS software to append RIF information, use the following command in interface configuration mode:
multiring {protocol-keyword [all-routes | spanning] | all | other}
Enables collection and use of RIF information.
For an example of how to configure the software to bridge routed protocols, see the "SRB and Routing Certain Protocols Example" section".
Configuring a Static RIF Entry
If a Token Ring host does not support the use of IEEE 802.2 TEST or XID datagrams as explorer packets, you might need to add static information to the RIF cache of the router.
To configure a static RIF entry, use the following command in global configuration mode:
rif mac-address rif-string {interface-name | ring-group ring}
Enters static source-route information into the RIF cache.
Configuring the RIF Timeout Interval
RIF information that can be used to bridge routed protocols is maintained in a cache whose entries are aged.
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To configure the number of minutes an inactive RIF entry is kept in the cache, use the following commands in global configuration mode:
Configuring Translation between SRB and Transparent Bridging Environments
Source-route translational bridging (SR/TLB) is a Cisco IOS software feature that allows you to combine SRB and transparent bridging networks without the need to convert all of your existing source-route bridges to source-route transparent (SRT) nodes. As such, it provides a cost-effective connectivity path between Ethernets and Token Rings, for example.
When a router is configured for SR/TLB, the router operates in fast-switching mode by default, causing packets to be processed in the interrupt handler when the packets first arrive, rather than queuing them for scheduled processing. You can also use the no source-bridge transparent fastswitch command to disable fast-switched SR/TLB, causing the router to handle packets by process switching. For more information on disabling fast-switched SR/TLB, refer to the "Disabling Fast-Switched SR/TLB" section in this chapter.
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Overview of SR/TLB
You can bridge packets between an SRB domain and a transparent bridging domain. Using this feature, a software "bridge" is created between a specified virtual ring group and a transparent bridge group. To the source-route station, this bridge looks like a standard source-route bridge. There is a ring number and a bridge number associated with a ring that actually represents the entire transparent bridging domain. To the transparent bridging station, the bridge represents just another port in the bridge group.
When bridging from the SRB (typically, Token Ring) domain to the transparent bridging (typically, Ethernet) domain, the source-route fields of the frames are removed. The RIFs are cached for use by subsequent return traffic.
When bridging from the transparent bridging domain to the SRB domain, the router checks the packet to see if it has a multicast or broadcast destination or a unicast (single host) destination. If it is multicast, the packet is sent as a spanning-tree explorer. If it is a unicast destination, the router looks up the path to the destination in the RIF cache. If a path is found, it will be used; otherwise, the router will send the packet as a spanning-tree explorer.
An example of a simple SR/TLB topology is shown in Figure 28.
Figure 28 Example of a Simple SR/TLB Topology
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The following notes and caveats apply to all uses of SR/TLB:
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Problems can occur with the following protocols when bridged between Token Ring and other media: Novell IPX, DECnet Phase IV, AppleTalk, VINES, XNS, and IP. Further, problems can occur with the Novell IPX and XNS protocols when bridged between FDDI and other media. Cisco recommends that these protocols be routed whenever possible.
To enable SR/TLB, you must perform the task in the following section:
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In addition, you can also perform the tasks in the following sections:
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Enabling Bridging between Transparent Bridging and SRB
Before enabling bridging, you must have completely configured your router using multiport SRB and transparent bridging. Once you have done this, establish bridging between transparent bridging and source-route bridging by using the following command in global configuration mode:
source-bridge transparent ring-group pseudo-ring bridge-number tb-group [oui]
Enables bridging between transparent bridging and SRB.
Disabling Fast-Switched SR/TLB
To disable fast-switched SR/TLB and cause the router to handle packets by process switching, use the following command in global configuration mode:
Enabling Translation Compatibility with IBM 8209 Bridges
To transfer data between IBM 8209 Ethernet/Token Ring bridges and routers running the SR/TLB software (to create a Token Ring backbone to connect Ethernets), use the following command on each Token Ring interface in interface configuration mode:
ethernet-transit-oui [90-compatible | standard | cisco]
Moves data between IBM 8209 Ethernet/Token Ring bridges and routers running translational bridging software.
Enabling Token Ring LLC2-to-Ethernet Conversion
The Cisco IOS software supports the following types of Token Ring-to-Ethernet frame conversions using Logical Link Control, type 2 (LLC2) Protocol:
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For most non-IBM hosts, Token Ring LLC2 frames can be translated in a straightforward manner into Ethernet 802.3 LLC2 frames. This is the default conversion in the Cisco IOS software.
However, many Ethernet-attached IBM devices use nonstandard encapsulation of LLC2 on Ethernet. Such IBM devices, including PS/2s running OS/2 Extended Edition and RT-PCs, do not place their LLC2 data inside an 802.3 format frame, but rather place it into an Ethernet Type 2 frame whose type is specified as 0x80d5. This nonstandard format is called 0x80d5, named after the type of frame. This format is also sometimes called RT-PC Ethernet format because these frames were first widely seen on the RT-PC. Hosts using this nonstandard 0x80d5 format cannot read the standard Token Ring LLC2 to Ethernet 802.2 LLC frames.
To enable Token Ring LLC2 to Ethernet LLC2 conversion, you can perform one or both of the following tasks:
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Enable 0x80d5 Processing
You can change the Cisco IOS software's default translation behavior of translating Token Ring LLC to Ethernet 802.3 LLC to translate Token Ring LLC2 frames into Ethernet 0x80d5 format frames. To enable this nonstandard conversion, use the following command in global configuration mode:
source-bridge enable-80d5
Changes the Ethernet/Token Ring translation behavior to translate Token Ring LLC2 frames into Ethernet 0x80d5 format frames.
Enable Standard Token Ring LLC2-to-Ethernet LLC2 Conversion
After you change the translation behavior to perform Token Ring LLC2 frames into Ethernet 0x80d5 format frames, some of the non-IBM hosts in your network topology might use the standard Token Ring conversion of Token Ring LLC2 to 802.3 LLC2 frames. If this is the case, you can change the translation method of those hosts to use the standard translation method on a per-DSAP basis. The translation method for all the IBM hosts would still remain as Token Ring LLC2 to Ethernet 0x80d5 translation.
To define non-IBM hosts in your network topology to use the standard translation method while the IBM hosts use the nonstandard method, use the following command in global configuration mode:
source-bridge sap-80d5 dsap
Allows some other devices to use normal LLC2/IEEE 802.3 translation on a per-DSAP basis.
Configuring NetBIOS Support
NetBIOS is a nonroutable protocol that was originally designed to transmit messages between stations, typically IBM PCs, on a Token Ring network. NetBIOS allows messages to be exchanged between the stations using a name rather than a station address. Each station knows its name and is responsible for knowing the names of other stations on the network.
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NetBIOS name caching allows the Cisco IOS software to maintain a cache of NetBIOS names, which avoids the high overhead of transmitting many of the broadcasts used between client and server NetBIOS PCs (IBM PCs or PS/2s) in an SRB environment.
When NetBIOS name caching is enabled, the software performs the following actions:
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The software will time out the entries in the NetBIOS name cache after a specific interval of their initial storage. The timeout value is a user-configurable value. You can configure the timeout value for a particular Token Ring if the NetBIOS name cache is enabled on the interface connecting to that Token Ring. In addition, you can configure static name cache entries that never time out for frequently accessed servers whose locations or paths typically do not change. Static RIF entries are also specified for such hosts.
Generally, NetBIOS name caching is most useful when a large amount of NetBIOS broadcast traffic creates bottlenecks on WAN media connecting distant locations, and the WAN media is overwhelmed with this traffic. However, when two high-speed LAN segments are directly interconnected, the packet savings of NetBIOS name caching is probably not worth the processor overhead associated with it.
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To enable NetBIOS name caching, you must perform the tasks in the following sections:
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In addition, you can configure NetBIOS name caching as described in the following sections:
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Enabling the Proxy Explorers Feature on the Appropriate Interface
To enable NetBIOS name caching on an interface, the proxy explorers feature must first be enabled on that interface. This feature must either be enabled for response to all explorer packets or for response to NetBIOS packets only.
To determine whether the proxy explorers feature has been enabled, use the following command in EXEC mode:
show startup-config
Determines whether or not the proxy explorers feature has been enabled.
To determine whether proxy explorers has been configured for response to all explorer packets, look in the configuration file for the source-bridge proxy-explorer entry for the appropriate interface. For example, if the appropriate interface is Token Ring 0, look for an entry similar to the following:
interface tokenring 0source-bridge proxy-explorerIf that entry does not exist, look for the source-bridge proxy-netbios-only entry for the appropriate interface.
If neither entry exists, proxy explorers has not yet been enabled for the appropriate interface. To enable proxy explorers for response to all explorer packets, refer to the section "Configure Proxy Explorers" later in this chapter.
Otherwise, enable proxy explorers only for the NetBIOS name caching function by using the following command in global configuration mode:
source-bridge proxy-netbios-only
Enables use of proxy explorers only for the NetBIOS name caching function and not for their general local response to explorers.
Specifying Timeout and Enabling NetBIOS Name Caching
After you have ensured that the proxy explorers feature has been enabled for the appropriate interface, you can specify a cache timeout and enable NetBIOS name caching. To do this, use the following commands in global configuration mode:
Configuring the NetBIOS Cache Name Length
To specify how many characters of the NetBIOS type name that the name cache will validate, use the following command in global configuration mode:
netbios name-cache name-len length
Specifies the number of characters of the NetBIOS type name to cache.
Enabling NetBIOS Proxying
The Cisco IOS software can act as a proxy and send NetBIOS datagram type frames. To enable this capability, use the following command in global configuration mode:
To define the validation time when the software is acting as a proxy for NetBIOS NAME_QUERY command or for explorer frames, use the following global configuration command:
Creating Static Entries in the NetBIOS Name Cache
If the router communicates with one or more NetBIOS stations on a regular basis, adding static entries to the NetBIOS name cache for these stations can reduce network traffic and overhead. You can define a static NetBIOS name cache entry that associates the server with the NetBIOS name and the MAC address. If the router acts as a NetBIOS server, you can specify that the static NetBIOS name cache is available locally through a particular interface. If a remote router acts as the NetBIOS server, you can specify that the NetBIOS name cache is available remotely. To do this, use one of the following commands in global configuration mode:
If you have defined a NetBIOS name cache entry, you must also define a RIF entry. For an example of how to configure a static NetBIOS entry, see the "NetBIOS Support with a Static NetBIOS Cache Entry Example" section later in this chapter.
Specifying Dead-Time Intervals for NetBIOS Packets
When NetBIOS name caching is enabled and default parameters are set on the router (as well as the NetBIOS name server and the NetBIOS name client), approximately 20 broadcast packets per login are kept on the local ring where they are generated. The broadcast packets are of the type ADD_NAME_QUERY, ADD_GROUP_NAME, and STATUS_QUERY.
The Cisco IOS software also converts pairs of FIND_NAME and NAME_RECOGNIZED packets received from explorers, which traverse all rings, to specific route frames that are sent only between the two machines that need to see these packets.
You can specify a query-timeout, or "dead-time" interval to prevent repeat or duplicate broadcast of these type of packets for the duration of the interval.
To specify dead time intervals, use one or both of the following commands in global configuration mode:
Configuring LNM Support
LAN Network Manager (LNM), formerly called LAN Manager, is an IBM product for managing a collection of source-route bridges. Using either a proprietary protocol or the Simple Network Management Protocol (SNMP), LNM allows you to monitor the entire collection of Token Rings that comprise your source-route bridged network. You can use LNM to manage the configuration of source-route bridges, monitor Token Ring errors, and gather information from Token Ring parameter servers.
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LNM is not limited to managing locally attached Token Ring networks; it also can manage any other Token Rings in your source-route bridged network that are connected through non-Token Ring media. To accomplish this task, LNM works in conjunction with the IBM Bridge Program. The IBM Bridge Program gathers data about the local Token Ring network and relays it back to LNM. In this manner, the bridge program becomes a proxy for information about its local Token Ring. Without this ability, you would require direct access to a device on every Token Ring in the network. This process would make managing an SRB environment awkward and cumbersome.
Figure 29 shows some Token Rings attached through a cloud and one LNM linking to a source-route bridge on each local ring.
Figure 29 LNM Linking to a Source-Route Bridge on Each Local Ring
If LNM requires information about a station somewhere on a Token Ring, it uses a proprietary IBM protocol to query to one of the source-route bridges connected to that ring. If the bridge can provide the requested information, it simply responds directly to LNM. If the bridge does not have the necessary information, it queries the station using a protocol published in the IEEE 802.5 specification. In either case, the bridge uses the proprietary protocol to send a valid response back to LNM, using the proprietary protocol.
As an analogy, consider a language translator who sits between a French-speaking diplomat and a German-speaking diplomat. If the French diplomat asks the translator a question in French for the German diplomat and the translator knows the answer, he or she simply responds without translating the original question into German. If the French diplomat asks a question the translator does not know how to answer, the translator must first translate the question to German, wait for the German diplomat to answer, and then translate the answer back to French.
Similarly, if LNM queries a source-route bridge in the proprietary protocol and the bridge knows the answer, it responds directly using the same protocol. If the bridge does not know the answer, it must first translate the question to the IEEE 802.5 protocol, query the station on the ring, and then translate the response back to the proprietary protocol to send to LNM.
Figure 30 illustrates requests from the LNM originating in an IBM proprietary protocol and then translated into IEEE 802.5 MAC-level frames.
Figure 30 LAN Network Manager Monitoring and Translating
Notice that the proprietary protocol LNM uses to communicate with the source-route bridge is an LLC2 connection. Although its protocol cannot be routed, LNM can monitor or manage anything within the SRB network.
How a Router Works with LNM
Cisco routers using 4/16-Mbps Token Ring interfaces configured for SRB support the proprietary protocol that LNM uses. These routers provide all functions the IBM Bridge Program currently provides. Thus LNM can communicate with a router as if it were an IBM source-route bridge, such as the IBM 8209, and can manage or monitor any Token Ring connected to the router.
Through IBM Bridge support, LNM provides three basic services for the SRB network:
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IBM Bridge support for LNM also allows asynchronous notification of some events that can occur on a Token Ring. Examples of these events include notification of a new station joining the Token Ring or of the ring entering failure mode, known as beaconing. Support is also provided for LNM to change the operating parameters in the bridge. For a complete description of LNM, refer to the IBM product manual supplied with the LNM program.
LNM support in our source-route bridges is a powerful tool for managing SRB networks. Through the ability to communicate with LNM and to provide the functionality of the IBM Bridge Program, our device appears as part of the IBM network. You therefore gain from the interconnectivity of our products without having to learn a new management product or interface.
When SRB is enabled on the router, configuring the Cisco IOS software to perform the functions of an IBM Bridge for communication with LNM occurs automatically. Therefore, if SRB has been enabled, you do not need to perform any tasks to enable LNM support. However, the LNM software residing on a management station on a Token Ring on the network should be configured to properly communicate with the router.
There are several options for modifying LNM parameters in the Cisco IOS software, but none are required for basic functionality. For example, because users can now modify the operation of the Cisco IOS software through SNMP as well as through LNM, there is an option to exclude a user from modifying the Cisco IOS software configuration through LNM. You also can specify which of the three LNM services (CRS, REM, RPS) the source-route bridge will perform.
To configure LNM support, perform the tasks in the following sections:
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