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This chapter describes how to configure Token Ring switching on the Catalyst 5000 series switch. The Token Ring modules have 16 shielded RJ-45 (copper) or Volition (fiber) ports for Token Ring connections. These ports allow full- or half-duplex connections to other switches, hubs, or end nodes.
This chapter consists of these sections:
These sections describe how Token Ring switching works:
The Catalyst 5000 series Token Ring modules provide these features:
In addition to the standard Management Information Base (MIB) objects supported by the Catalyst 5000 series switch, the Token Ring modules support these additional MIBs:
The proprietary MIBs supported are:
Most user-configurable variables are supported in either the standard MIBs or private MIBs.
A source-route bridge makes all forwarding decisions based on data in the Routing Information Field (RIF). It does not learn or look up Media Access Control (MAC) addresses; SRB frames without a RIF are not forwarded.
Typically, clients or servers that support source routing send an explorer frame to determine the path to a given destination. There are two types of explorer frames: All-Routes Explorer and Spanning-Tree Explorer. All SRB bridges copy All-Routes Explorer frames and add their own routing information. For frames that are received from or sent to ports that are in the spanning-tree forwarding state, bridges copy Spanning-Tree Explorer frames and add their own routing information. Because All-Routes Explorer frames will traverse all paths between two devices, they are used in path determination. Spanning-Tree Explorer frames are used to send datagrams because the spanning tree ensures that only one copy of a Spanning-Tree Explorer frame is sent to each ring.
SRT bridging is an IEEE standard that combines source-route bridging and transparent bridging. An SRT bridge forwards frames that do not contain a RIF based on the destination MAC address. Frames that contain a RIF are forwarded based upon source routing. The SRT bridge only runs the IEEE Spanning-Tree Protocol. SRT does not support the IBM Spanning-Tree Protocol.
The Token Ring modules can forward broadcast, multicast, and unicast frames based on MAC addresses. If you have source-route bridges in your network, the Token Ring modules can forward frames based on the RIF. This dual frame-forwarding technology is called source-route switching.
In source-route switching, the switch learns and forwards frames based on source-route descriptors for stations that are one or more source-route bridge hops away. A route descriptor is a portion of a RIF that indicates a single hop. It is defined as a ring number and a bridge number. When a source-routed frame enters the switch, the switch learns the route descriptor for the hop closest to the switch. Frames received from other ports with the same next-hop route descriptor as their destination are forwarded to that port.
The key difference between SRB and source-route switching is that while a source-route switch looks at the RIF, it never updates the RIF. Therefore, all ports in a source-route switch group have the same ring number.
Source-route switching provides the following benefits:
To set the bridging mode of a Token Ring Concentrator Relay Function (TrCRF), perform this task in privileged mode:
| Task | Command |
|---|---|
Set the bridging mode. | set vlan vlan_num [mode {srt | srb}] |
The Token Ring modules support a new token-passing standard called Dedicated Token Ring (DTR). DTR is the IEEE 802.5R standard that:
DTR provides improved access to central resources, such as network servers. The server can use the full 16 Mbps available for sending and receiving, resulting in an aggregate bandwidth of 32 Mbps.
Table 46-1 shows the Token Ring default configuration.
| Feature | Default Value |
|---|---|
Port enable state | All ports are enabled |
Port name | None |
Port priority | Normal |
Port speed | Auto-detect |
Duplex mode | Autonegotiate half- or full-duplex mode |
Transmission threshold | 3 |
Minimum transmit setting | 4 |
VLAN | All ports assigned to default TrCRF |
Spanning-Tree Protocol | Enabled for all ports |
All-Routes Explorer reduction | Enabled |
These sections describe how to configure Token Ring switching:
 | Caution Changing certain configuration parameters of a connected port will cause the port to close and reopen. You will lose all address information and statistics for that port. |
To assign a name to a port on the Token Ring module, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Assign a name to a port. | set port name mod_num/port_num name |
Step 2 Verify that the port name is configured. | show port [mod_num[/port_num]] |
This example shows how to set the name for a port and how to verify the name assignment:
Console> (enable) set port name 3/2 Print-1st Floor Port 3/2 name set. Console> (enable) show port 3/2 Port Name Status Vlan Level Duplex Speed Type ----- ------------------ ---------- ---------- ------ ------ ----- ------------ 3/2 Print-1st Floor inactive 1003 normal fdx 16 TokenRing Last-Time-Cleared -------------------------- Wed May 6 1998, 18:09:47 Console> (enable)
To address the needs of delay-sensitive data, each port on a Token Ring module has two data queues: high-priority and low-priority queues.
The queue is determined by the value of the priority field in the frame control (FC) byte of the frame. If the FC priority is above the user-defined priority level, the frame is put in the high-priority queue and is transmitted using the frame priority. If the FC priority is at or below the user-defined priority level, the frame is sent to the low-priority queue.
You can set two types of frame priorities for a port:
To set the frame priority levels for a port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Set the frame priority levels for a port. | set tokenring priority mod_num/port_num {threshold 0-7 | minxmit 0-6} |
Step 2 Verify the priority configuration. | show tokenring [mod_num[/port_num]] |
This example shows how to set the Token Ring priority threshold to 6 on a port:
Console> (enable) set tokenring priority 3/2 threshold 6 Port 2 priority threshold set to 6. Console> (enable) show tokenring 3/2 Ports Crf/Brf Ring# Port-Mode Early-Token AC-bits ----- --------- ----- ------------- ----------- -------- 3/2 1003/1005 3276 fdx-cport enabled disabled Ports Prior-Thresh Min-Xmit MAC-Address ----- ------------ -------- ----------------- 3/2 6 5 00:40:0b:01:bc:65 Ports Cfg-Loss-Thresh Cfg-Loss-Intvl Cfg-Loss-Count Cfg-Loss-Reason ----- --------------- -------------- -------------- --------------- 3/2 50 20 0 none Console> (enable)
The Token Ring modules support 4- and 16-Mbps Token Ring transmission speeds. You can configure ports on the Token Ring modules to operate at one of these speeds or to automatically sense the speed of the ring to which it is connected (the default setting). However, with Token Ring technology, you cannot change the transmission speed without closing and reopening the port. These rules apply:
To set the transmission speed for a port on the Token Ring module, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Set the transmission speed for a Token Ring module port. | set port speed mod_num/port_num {4 | 16 | auto} |
Step 2 Verify the port speed. | show port [mod_num[/port_num]] |
This example shows how to set the ring speed for a port and verify the configuration:
Console> (enable) set port speed 3/2 16 Port 3/2 speed set to 16Mbps. Console> (enable) show port 3/2 Port Name Status Vlan Level Duplex Speed Type ----- ------------------ ---------- ---------- ------ ------ ----- ------------ 3/2 Print-1st Floor inactive 1003 normal fdx 16 TokenRing Last-Time-Cleared -------------------------- Wed May 6 1998, 18:09:47 Console> (enable)
Each port on the Token Ring module can operate in one of these modes:
The default mode, auto, enables the port to detect the transmission mode it needs to use. However, you can configure the mode if necessary.
To set the transmission mode for a port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Set the transmission mode for a port. | set tokenring portmode mod_num/port_num {auto | fdxcport | hdxcport | fdxstation | |
Step 2 Verify the transmission mode setting. | show tokenring [mod_num[/port_num]] |
This example shows how to set the transmission mode for a port and verify the configuration:
Console> (enable) set tokenring portmode 3/2 fdxcport Port 3/2 mode set to fdxcport Console> (enable) show tokenring 3/2 Ports Crf/Brf Ring# Port-Mode Early-Token AC-bits ----- --------- ----- ------------- ----------- -------- 3/2 1003/1005 3276 fdx-cport enabled disabled Ports Prior-Thresh Min-Xmit MAC-Address ----- ------------ -------- ----------------- 3/2 6 5 00:40:0b:01:bc:65 Ports Cfg-Loss-Thresh Cfg-Loss-Intvl Cfg-Loss-Count Cfg-Loss-Reason ----- --------------- -------------- -------------- --------------- 3/2 50 20 0 none
The interface ports on the Token Ring modules support early token release. Early token release allows a station to release a new token onto the ring immediately after transmitting, instead of waiting for the first frame to return. Early token release increases the total bandwidth on the ring. All ports, by default, are enabled to use early token release.
To enable the early token release feature on a Token Ring module port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Enable the early token release feature on a Token Ring module port. | set tokenring etr mod_num/port_num enable |
Step 2 Verify the early token release configuration. | show tokenring [mod_num[/port_num]] |
This example shows how to enable early token release and verify the configuration:
Console> (enable) set tokenring etr 3/2 enable Port 3/2 Early Token Release enabled. Console> (enable) show tokenring 3/2 Ports Crf/Brf Ring# Port-Mode Early-Token AC-bits ----- --------- ----- ------------- ----------- -------- 3/2 1003/1005 3276 fdx-cport enabled disabled Ports Prior-Thresh Min-Xmit MAC-Address ----- ------------ -------- ----------------- 3/2 6 5 00:40:0b:01:bc:65 Ports Cfg-Loss-Thresh Cfg-Loss-Intvl Cfg-Loss-Count Cfg-Loss-Reason ----- --------------- -------------- -------------- --------------- 3/2 50 20 0 none Console> (enable)
To disable the early token release feature on a Token Ring module port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Disable early token release on a Token Ring module port. | set tokenring etr mod_num/port_num disable |
Step 2 Verify the early token release configuration. | show tokenring [mod_num[/port_num]] |
You can specify whether the address-recognized (A) bit and the frame-copied (C) bit should be set unconditionally on repeated source-routed Logical Link Control (LLC) frames. These include source-routed frames with a RIF length greater than 2 and all Spanning-Tree Explorer and All-Routes Explorer frames. The default is disable. If this parameter is disable, the setting of these bits is based on whether the frame was actually forwarded.
To set the AC bits for a port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Set the AC bits for a port. | set tokenring acbits mod_num/port_num {enable | disable} |
Step 2 Verify the AC bits setting for a port. | show tokenring [mod_num[/port_num]] |
This example shows how to set the AC bits for a port and how to verify the configuration:
Console> (enable) set tokenring acbits 3/2 enable Port 3/2 acbits enabled. Console> (enable) show tokenring 3/2 Ports Crf/Brf Ring# Port-Mode Early-Token AC-bits ----- --------- ----- ------------- ----------- -------- 3/2 1003/1005 3276 fdx-cport enabled enabled Ports Prior-Thresh Min-Xmit MAC-Address ----- ------------ -------- ----------------- 3/2 6 5 00:40:0b:01:bc:65 Ports Cfg-Loss-Thresh Cfg-Loss-Intvl Cfg-Loss-Count Cfg-Loss-Reason ----- --------------- -------------- -------------- --------------- 3/2 50 20 0 none Console> (enable)
Configuration loss occurs when a port completes a connection, allows data traffic to flow, and subsequently closes. The configuration loss threshold controls the number of configuration losses that can occur within a specified time. When the threshold is exceeded, the port is disabled and you must enable it by entering the set port enable command or an SNMP manager. The valid range for the configuration loss threshold is 1 through 100. The default is 8.
To set and verify the configuration loss threshold for a port, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Set the configuration loss threshold for a port. | set tokenring configloss mod_num/port_num {threshold <1..100> | interval <1..9999>} |
Step 2 Verify the configuration loss threshold setting. | show tokenring [mod_num[/port_num]] |
This example shows how to set the configuration loss threshold for a port and verify the configuration:
Console> (enable) set tokenring configloss 3/2 threshold 50 Port 3/2 configloss threshold set to 50. Console> (enable) set tokenring configloss 3/2 interval 20 Port 3/2 configloss interval set to 20. Console> (enable) show tokenring 3/2 Ports Crf/Brf Ring# Port-Mode Early-Token AC-bits ----- --------- ----- ------------- ----------- -------- 3/2 1003/1005 3276 fdx-cport enabled enabled Ports Prior-Thresh Min-Xmit MAC-Address ----- ------------ -------- ----------------- 3/2 6 5 00:40:0b:01:bc:65 Ports Cfg-Loss-Thresh Cfg-Loss-Intvl Cfg-Loss-Count Cfg-Loss-Reason ----- --------------- -------------- -------------- --------------- 3/2 50 20 0 none Console> (enable)
For parallel SRB or SRT backbones, All-Routes Explorer reduction ensures that the number of All-Routes Explorer frames generated by the switch does not overwhelm the network.
In accordance with the IEEE 802.1d SRT standard, the Token Ring module discards any All-Routes Explorer frames that have already been on a ring attached to the switch. This ensures that only one All-Routes Explorer frame is received on each ring within each VLAN (Token Ring Bridge Relay Function [TrBRF] and Token Ring Concentrator Relay Function [TrCRF]). The number of frames is equal to the number of external parallel paths between the rings. If a port on the switch fails or is disabled, the switch no longer checks for this ring number in the RIF. This bypass allows frames to travel on alternate paths.
By default, All-Routes Explorer reduction is enabled.
To enable All-Routes Explorer reduction, perform this task in privileged mode:
| Task | Command |
|---|---|
Enable All-Routes Explorer reduction. | set tokenring reduction enable |
To disable All-Routes Explorer reduction, perform this task in privileged mode:
| Task | Command |
|---|---|
Disable All-Routes Explorer reduction. | set tokenring reduction disable |
Posted: Tue Mar 30 16:16:11 PST 1999
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