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Bridging and IBM Networking Configuration Guide
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About The Cisco IOS Software Documentation
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Bridging and IBM Networking Overview
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Configuring Transparent Bridging
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Configuring Source-Route Bridging
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Configuring Remote Source-Route Bridging
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Configuring DLSw+
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Configuring STUN and BSTUN
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Configuring LLC2 and SDLC Parameters
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Configuring IBM Network Media Translation
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Configuring DSPU and SNA Service Point Support
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Configuring SNA Frame Relay Access Support
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Configuring APPN
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Configuring IBM Channel Attach
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Table Of Contents
Specify an SDLC Transmission Group
Create and Specify a Custom STUN Protocol
Establish the Frame Encapsulation Method
Configure HDLC Encapsulation without Local Acknowledgment
Configure TCP Encapsulation without Local Acknowledgment
Configure TCP Encapsulation with SDLC Local Acknowledgment and Priority Queuing
Assign the Router an SDLC Primary or Secondary Role
Enable the SDLC Local Acknowledgment Feature
Establish Priority Queuing Levels
Configure Local Acknowledgment for Direct Frame Relay Connectivity
Configure STUN with Multilink Transmission Groups
Set Up STUN Traffic Priorities
Prioritize by Serial Interface Address or TCP Port
Prioritize by Logical Unit Address
Prioritize STUN Traffic over All Other Traffic
Configuring STUN Priorities Using HDLC Encapsulation Example
Configuring SDLC Broadcast Example
Configuring Serial Link Address Prioritization Using STUN TCP/IP Encapsulation Example
Configuring STUN Multipoint Implementation Using a Line-Sharing Device Example
Configuring STUN Local Acknowledgment for SDLC Example
Configuring STUN Local Acknowledgment for Frame Relay Example
Configuring LOCADDR Priority Groups—Simple Example
Configuring LOCADDR Priority Groups for STUN Example
Block Serial Tunneling (BSTUN)
Point-to-Point and Multidrop Support
Configure BSTUN on the Serial Interface
Place a Serial Interface in a BSTUN Group
Define How Frames are Forwarded
Set Up BSTUN Traffic Priorities
Configure BSC Options on a Serial Interface
Simple BSC Configuration Example
Priority Queuing: Prioritization Based on BSTUN Header Example
Priority Queuing: Prioritization Based on BSTUN Header and Packet Sizes Example
Priority Queuing: Prioritization Based on BSTUN Header and BSC Address Example
Priority Queuing: Prioritization Based on BSTUN TCP Ports Example
Priority Queuing: Prioritization Based on BSTUN TCP Ports and BSC Address Example
Custom Queuing: Prioritization Based on BSTUN Header Example
Custom Queuing: Prioritization Based on BSTUN Header and Packet Size Example
Custom Queuing: Prioritization Based on BSTUN Header and BSC Address Example
Custom Queuing: Prioritization Based on BSTUN TCP Ports Example
Custom Queuing: Prioritization Based on BSTUN TCP Ports and BSC Address Example
Configuring STUN and BSTUN
Cisco's serial tunnel (STUN) implementation allows Synchronous Data Link Control (SDLC) devices and High-Level Data Link Control (HDLC) devices to connect to one another through a multiprotocol internetwork. Cisco's block serial tunnel (BSTUN) encapsulates binary synchronous communication (BSC) traffic for transfer over router links.
For a complete description of the commands mentioned in this chapter, refer to the "STUN and BSTUN Commands" chapter in the Bridging and IBM Networking Command Reference.
STUN Configuration Task List
To configure and monitor STUN, or STUN local acknowledgment, complete the tasks in the following sections:
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Establish the Frame Encapsulation Method
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The "STUN Configuration Examples" section follows these configuration tasks.
Enable STUN
To enable STUN perform the following task in global configuration mode:
When configuring redundant links, ensure that the STUN peer names you choose on each router are the IP addresses of the most stable interfaces on each device, such as a loopback or Ethernet interface. See "STUN Configuration Examples" later in this chapter.
Configure SDLC Broadcast
The SDLC broadcast feature allows SDLC broadcast address FF to be replicated for each of the STUN peers, so each of the end stations receives the broadcast frame. For example, in , the FEP views the end stations 1, 2 and 3 as if they are on an SDLC multidrop link. Any broadcast frame sent from FEP to Router A is duplicated and sent to each of the downstream routers (B and C).
Figure 76 SDLC Broadcast across Virtual Multidrop Lines
To enable SDLC broadcast, perform the following task in interface configuration mode:
Only enable SDLC broadcast on the device that is configured to be the secondary station on the SDLC link (Router A in ).
You must also configure SDLC address FF on Router A for each of the STUN peers. To do so, perform the following task in interface configuration mode:
Configure SDLC address FF on Router A for each STUN peer.
stun route address address-number tcp ip-address [local-ack] [priority] [tcp-queue-max]
Specify STUN Protocol Group
Place ach STUN interface in a group that defines the ISO 3309-compliant framed protocol running on that link. Packets will only travel between STUN interfaces that are in the same protocol group.
There are three predefined STUN protocols:
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You also can specify a custom STUN protocol.
You must specify either the SDLC protocol or the SDLC transmission group protocol if you want to use the STUN Local Acknowledgment feature.
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Specify a Basic STUN Group
The basic STUN protocol is not dependent on the details of serial protocol addressing and is used when addressing is unimportant. Use this when your goal is to replace one or more sets of point-to-point (not multidrop) serial links by using a protocol other than SDLC. Perform the following task in global configuration mode:
Specify a basic protocol group and assign a group number.
stun protocol-group group-number basic
Specify an SDLC Group
You can specify SDLC protocol groups to associate interfaces with the SDLC protocol. Use the SDLC STUN protocol to place the routers in the midst of either point-to-point or multipoint (multidrop) SDLC links. To define an SDLC protocol group, perform the following task in global configuration mode:
Specify an SDLC protocol group and assign a group number.
stun protocol-group group-number sdlc
If you specify an SDLC protocol group, you cannot specify the stun route all command on any interface of that group.
For an example of how to configure an SDLC protocol group, see the "Configuring Serial Link Address Prioritization Using STUN TCP/IP Encapsulation Example" later in this chapter.
Specify an SDLC Transmission Group
An SNA transmission group is a set of lines providing parallel links to the same pair of SNA front-end-processor (FEP) devices. This provides redundancy of paths for fault tolerance and load sharing. To define an SDLC transmission group, perform the following task in global configuration mode:
Specify an SDLC protocol group, assign a group number, and create an SNA transmission group.
stun protocol-group group-number sdlc sdlc-tg
All STUN connections in a transmission group must connect to the same IP address and use the SDLC local acknowledgment feature.
Create and Specify a Custom STUN Protocol
To define a custom protocol and tie STUN groups to the new protocol, perform the following tasks in global configuration mode:
Enable STUN Keepalive
To define the number of times to attempt a peer connection before declaring the peer connection be down, perform the following task in global configuration mode::
Enable STUN Remote Keepalive
To enable detection of the loss of a peer, perform the following task in global configuration mode::
Enable STUN Quick-Response
You can enable STUN quick-response, which improves network performance when used with local acknowledgment. When STUN quick-response is used with local acknowledgment, the router responds to an exchange identification (XID) or a Set Normal Response Mode (SNRM) request with a Disconnect Mode (DM) response when the device is not in the CONNECT state. The request is then passed to the remote router and, if the device responds, the reply is cached. The next time the device is sent an XID or SNRM, the router replies with the cached DM response.
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To enable STUN quick-response, perform the following task in global configuration mode:
Enable STUN Interfaces
You must enable STUN on serial interfaces and place these interfaces in the protocol groups you have defined. To enable STUN on an interface and to place the interface in a STUN group, perform the following tasks in interface configuration mode:
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encapsulation stun
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stun group group-number
When a given serial link is configured for the STUN function, it is no longer a shared multiprotocol link. All traffic that arrives on the link will be transported to the corresponding peer as determined by the current STUN configuration.
Establish the Frame Encapsulation Method
To allow SDLC frames to travel across a multimedia, multiprotocol network, you must encapsulate them using one of the methods in the following sections:
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Configure HDLC Encapsulation without Local Acknowledgment
You can encapsulate SDLC or HDLC frames using the HDLC protocol. The outgoing serial link still can be used for other kinds of traffic. The frame is not TCP encapsulated. To configure HDLC encapsulation, perform one of the following tasks in interface configuration mode:
Use the no forms of these commands to disable HDLC encapsulation.
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Configure TCP Encapsulation without Local Acknowledgment
If you do not want to use SDLC local acknowledgment and only need to forward all SDLC frames encapsulated in TCP, complete the following tasks in interface configuration mode:
Use the no form of these commands to disable forwarding of all TCP traffic.
This configuration is typically used when two routers can be connected via an IP network as opposed to a point-to-point link.
Configure TCP Encapsulation with SDLC Local Acknowledgment and Priority Queuing
You configure SDLC local acknowledgment using TCP encapsulation. When you configure SDLC local acknowledgment, you also have the option to enable support for priority queuing.
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SDLC local acknowledgment provides local termination of the SDLC session so that control frames no longer travel the WAN backbone networks. This means that time-outs are less likely to occur.
illustrates an SDLC session. IBM 1, using a serial link, can communicate with IBM 2 on a different serial link separated by a wide-area backbone network. Frames are transported between Router A and Router B using STUN. However, the SDLC session between IBM 1 and IBM 2 is still end-to-end. Every frame generated by IBM 1 traverses the backbone network to IBM 2, which, upon receipt of the frame, acknowledges it.
Figure 77 SDLC Session without Local Acknowledgment
With SDLC local acknowledgment, the SDLC session between the two end nodes is not end-to-end but instead terminates at the two local routers, as shown in Figure 78. The SDLC session with IBM 1 ends at Router A, and the SDLC session with IBM 2 ends at Router B. Both Router A and Router B execute the full SDLC protocol as part of SDLC Local Acknowledgment. Router A acknowledges frames received from IBM 1. The node IBM 1 treats the acknowledgments it receives as if they are from IBM 2. Similarly, Router B acknowledges frames received from IBM 2. The node IBM 2 treats the acknowledgments it receives as if they are from IBM 1.
Figure 78 SDLC Session with Local Acknowledgment
To configure TCP encapsulation with SDLC local acknowledgment and priority queuing, perform the tasks in the following sections:
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Assign the Router an SDLC Primary or Secondary Role
To establish local acknowledgment, the router must play the role of an SDLC primary or secondary node. Primary nodes poll secondary nodes in a predetermined order. Secondaries then transmit if they have outgoing data.
For example, in the IBM environment, an FEP is the primary station and cluster controllers are secondary stations. If the router is connected to a cluster controller, the router should appear as an FEP and must therefore be assigned the role of a primary SDLC node. If the router is connected to an FEP, the router should appear as a cluster controller and must therefore be assigned the role of a secondary SDLC node. Devices connected to SDLC primary end-stations must play the role of an SDLC secondary and routers attached to SDLC secondary end stations must play the role of an SDLC primary station.
To assign the router a primary or secondary role, perform one of the following tasks in interface configuration mode:
Assign the STUN-enabled router an SDLC primary role.
stun sdlc-role primary
Assign the STUN-enabled router an SDLC secondary role.
stun sdlc-role secondary
Enable the SDLC Local Acknowledgment Feature
To enable SDLC local acknowledgment, complete the following task in interface configuration mode:
Establish SDLC local acknowledgment using TCP encapsulation.
stun route address address-number tcp ip-address [local-ack] [priority] [tcp-queue-max]
The stun route address 1 tcp local-ack priority tcp-queue-max interface configuration command enables local acknowledgment and TCP encapsulation. Both options are required to use transmission groups. You should specify the SDLC address with the echo bit turned off for transmission group interfaces. The SDLC broadcast address 0xFF is routed automatically for transmission group interfaces. The priority keyword creates multiple TCP sessions for this route. The tcp-queue-max keyword sets the maximum size of the outbound TCP queue for the SDLC. The default TCP queue size is 100. The value for hold-queue in should be greater than the value for tcp-queue-max.
You can use the priority keyword (to set up the four levels of priorities to be used for TCP encapsulated frames) at the same time you enable local acknowledgment. The priority keyword is described in the following section. Use the no form of this command to disable SDLC Local Acknowledgment. For an example of how to enable local acknowledgment, see "Configuring Serial Link Address Prioritization Using STUN TCP/IP Encapsulation Example" later in this chapter.
Establish Priority Queuing Levels
With SDLC local acknowledgment enabled, you can establish priority levels used in priority queuing for serial interfaces. The priority levels are as follows:
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To set the priority queuing level, perform the following task in interface configuration mode:
Establish the four levels of priorities to be used in priority queuing.
stun route address address-number tcp ip-address [local-ack] priority [tcp-queue-max]
Use the no form of this command to disable priority settings. For an example of how to establish priority queuing levels, see "Configuring Serial Link Address Prioritization Using STUN TCP/IP Encapsulation Example" later in this chapter.
Configure Local Acknowledgment for Direct Frame Relay Connectivity
To implement STUN with local acknowledgment using direct Frame Relay encapsulation, perform the following task in interface configuration mode:
Configure Frame Relay encapsulation between STUN peers with local acknowledgment.
stun route address sdlc-addr interface frame-relay-port dlci number localsap local-ack cls
Configure STUN with Multilink Transmission Groups
You can configure multilink SDLC transmission groups across STUN connections between IBM communications controllers such as IBM 37x5s. Multilink transmission group allow you to collapse multiple WAN leased lines into one leased line.
SDLC multilink transmission groups provide the following features:
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STUN connections that are part of a transmission group must have local acknowledgment enabled. Local acknowledgment keeps SDLC poll traffic off the WAN and reduces store-and-forward delays through the router. It also might minimize the number of NCP timers that expire due to network delay. Also, these STUN connections must go to the same IP address. This is because SNA transmission groups are parallel links between the same pair of IBM communications controllers.
Design Recommendations
This section provides some recommendations that are useful in configuring SDLC multilink transmission groups.
The bandwidth of the WAN should be larger than or equal to the aggregate bandwidth of all serial lines to avoid excessive flow control and ensure response timed does not degrade. If other protocols also are using the WAN, ensure that the WAN bandwidth is significantly greater than the aggregate SNA serial line bandwidth to ensure that the SNA traffic does not monopolize the WAN.
When you use a combination of routed transmission groups and directly connected NCP transmission groups, you need to plan the configuration carefully to ensure that SNA sessions do not stop unexpectedly. Assuming that hardware reliability is not an issue, single-link routed transmission groups are as reliable as direct NCP-to-NCP single-link transmission groups. This is true because neither the NCP nor the Cisco IOS software can reroute I-frames when a transmission group has only one link. Additionally, a multilink transmission group directed between NCPs and a multilink transmission group through a router are equally reliable. Both can perform rerouting.
However, you might run into problems if you have a configuration in which two NCPs are directly connected (via one or more transmission group links) and one link in the transmission group is routed. The NCPs treat this as a multilink transmission group. However, the Cisco IOS software views the transmission group as a single-link transmission group.
A problem can arise in the following situation: Assume that an I-frame is being transmitted from NCP A (connected to router A) to NCP B (connected to router B) and that all SDLC links are currently active. Router A acknowledges the I-frame sent from NCP A and sends it over the WAN. If, before the I-frame reaches Router B, the SDLC link between router B and NCP B goes down, Router B attempts to reroute the I-frame on another link in the transmission group when it receives the I-frame. However, because this is a single-link transmission group, there are no other routes, and Router B drops the I-frame. NCP B never receives this I-frame because Router A acknowledges its receipt, and NCP A marks it as transmitted and deletes it. NCP B detects a gap in the transmission group sequence numbers and waits to receive the missing I-frame. NCP B waits forever for this I-frame, and does not send or receive any other frames. NCP B is technically inoperational and all SNA sessions through NCP B are lost.
Finally, consider a configuration in which one or more lines of an NCP transmission group are connected to a router and one or more lines are directly connected between NCPs. If the network delay associated with one line of an NCP transmission group is different from the delay of another line in the same NCP transmission group, the receiving NCP spends additional time resequencing PIUs.
Set Up STUN Traffic Priorities
Use the methods described in the following sections to determine the order in which traffic should be handled on the network:
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Assign Queuing Priorities
You can assign queuing priorities by one of the following:
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Prioritize by Serial Interface Address or TCP Port
You can prioritize traffic on a per-serial-interface address or TCP port basis. You might want to do this so that traffic between one source-destination pair is always sent before traffic between another source-destination pair.
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To prioritize traffic, perform one of the following tasks in global configuration mode:
You must also perform the following task in interface configuration mode:
Figure 79 illustrates serial link address prioritization. Device A communicates with Device C, and Device B communicates with Device D. With the serial link address prioritization, you can choose to give A-C a higher priority over B-D across the serial tunnel.
Figure 79 Serial Link Address Prioritization
To disable priorities, use the no forms of these commands.
For an example of how to prioritize traffic according to serial link address, see "Configuring Serial Link Address Prioritization Using STUN TCP/IP Encapsulation Example" later in this chapter.
Prioritize by Logical Unit Address
SNA local logical unit (LU) address prioritization is specific to IBM SNA connectivity and is used to prioritize SNA traffic on either STUN or remote source-route bridging (RSRB). To set the queuing priority by LU address, perform the following task in interface configuration mode:
Assign a queuing priority based on the logical unit address.
locaddr-priority-list list-number address-number queue-keyword
In , LU address prioritization can be set so that particular LUs receive data in preference to others or so that LUs have priority over the printer, for example.
Figure 80 SNA LU Address Prioritization
To disable this priority, use the no form of this command.
For an example of how to prioritize traffic according to logical unit address, see "Configuring LOCADDR Priority Groups for STUN Example" later in this chapter.
Prioritize STUN Traffic over All Other Traffic
You can prioritize STUN traffic to be routed first before all other traffic on the network. To give STUN traffic this priority, perform the following task in global configuration mode:
Prioritize STUN traffic in your network over that of other protocols.
priority-list list-number stun queue address group-number address-number
To disable this priority, use the no form of this command.
For an example of how to prioritize STUN traffic over all other traffic, see "Configuring Serial Link Address Prioritization Using STUN TCP/IP Encapsulation Example" later in this chapter.
Monitor STUN Network Activity
You can list statistics regarding STUN interfaces, protocol groups, number of packets sent and received, local acknowledgment states, and more. To get activity information, perform the following task in EXEC mode:
STUN Configuration Examples
The following sections provide STUN configuration examples:
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Configuring STUN Priorities Using HDLC Encapsulation Example
Assume that the link between Router A and Router B in is a serial tunnel that uses the simple serial transport mechanism. Device A communicates with Device C (SDLC address C1) with a high priority. Device B communicates with Device D (SDLC address A7) with a normal priority.
Figure 81 STUN Simple Serial Transport
The following configurations set the priority of STUN hosts A, B, C, and D.
Configuration for Router A
stun peer-name 1.0.0.1stun protocol-group 1 sdlcstun protocol-group 2 sdlc!interface serial 0no ip addressencapsulation stunstun group 1stun route address C1 interface serial 2!interface serial 1no ip addressencapsulation stunstun group 2stun route address A7 interface serial 2!interface serial 2ip address 1.0.0.1 255.0.0.0priority-group 1!priority-list 1 stun high address 1 C1priority-list 1 stun low address 2 A7Configuration for Router B
stun peer-name 1.0.0.2stun protocol-group 1 sdlcstun protocol-group 2 sdlc!interface serial 0no ip addressencapsulation stunstun group 1stun route address C1 interface serial 1!interface serial 1ip address 1.0.0.2 255.0.0.0priority-group 1!interface serial 2no ip addressencapsulation stunstun group 2stun route address A7 interface serial 1!priority-list 1 stun high address 1 C1priority-list 1 stun low address 2 A7Configuring SDLC Broadcast Example
In the following example, an FEP views end stations 1, 2, and 3 as if they were on an SDLC multidrop link. Any broadcast frame sent from the FEP to Router A is duplicated and sent to each of the downstream routers (B and C):
stun peer-name xxx.xxx.xxx.xxxstun protocol-group 1 sdlcinterface serial 1encapsulation stunstun group 1stun sdlc-role secondarysdlc virtual-multidropsdlc address 1sdlc address 2sdlc address 3stun route address 1 tcp yyy.yyy.yyy.yyy local-ackstun route address 2 tcp zzz.zzz.zzz.zzz local-ackstun route address 3 tcp zzz.zzz.zzz.zzz local-ackstun route address FF tcp yyy.yyy.yyy.yyystun route address FF tcp zzz.zzz.zzz.zzzConfiguring Serial Link Address Prioritization Using STUN TCP/IP Encapsulation Example
Assume that the link between Router A and Router B is a serial tunnel that uses the TCP/IP encapsulation as shown in . Device A communicates with Device C (SDLC address C1) with a high priority. Device B communicates with Device D (SDLC address A7) with a normal priority. The configuration file for each router follows the figure.
Figure 82 STUN TCP/IP Encapsulation
Configuration for Router A
stun peer-name 1.0.0.1stun protocol-group 1 sdlcstun protocol-group 2 sdlc!interface serial 0no ip addressencapsulation stunstun group 1stun route address C1 tcp 1.0.0.2 local-ack prioritypriority-group 1!interface serial 1no ip addressencapsulation stunstun group 2stun route address A7 tcp 1.0.0.2 local-ack prioritypriority-group 2!interface ethernet 0ip address 1.0.0.1 255.0.0.0!interface ethernet 1ip address 1.0.0.3 255.0.0.0!priority-list 1 protocol ip high tcp 1994priority-list 1 protocol ip medium tcp 1990priority-list 1 protocol ip normal tcp 1991priority-list 1 protocol ip low tcp 1992priority-list 1 stun high address 1 C1!priority-list 2 protocol ip high tcp 1994priority-list 2 protocol ip medium tcp 1990priority-list 2 protocol ip normal tcp 1991priority-list 2 protocol ip low tcp 1992priority-list 2 stun normal address 2 A7!hostname routerArouter igrpnetwork 1.0.0.0Configuration for Router B
stun peer-name 1.0.0.2stun protocol-group 1 sdlcstun protocol-group 2 sdlc!interface serial 0no ip addressencapsulation stunstun group 1stun route address C1 tcp 1.0.0.1 local-ack prioritypriority-group 1!interface serial 2no ip addressencapsulation stunstun group 2stun route address A7 tcp 1.0.0.1 local-ack prioritypriority-group 2!interface ethernet 0ip address 1.0.0.2 255.0.0.0!interface ethernet 1ip address 1.0.0.4 255.0.0.0!priority-list 1 protocol ip high tcp 1994priority-list 1 protocol ip medium tcp 1990priority-list 1 protocol ip normal tcp 1991priority-list 1 protocol ip low tcp 1992priority-list 1 stun high address 1 C1!priority-list 2 protocol ip high tcp 1994priority-list 2 protocol ip medium tcp 1990priority-list 2 protocol ip normal tcp 1991priority-list 2 protocol ip low tcp 1992priority-list 2 stun normal address 2 A7!hostname routerBrouter igrp 109network 1.0.0.0Configuring STUN Multipoint Implementation Using a Line-Sharing Device Example
In Figure 83, four separate PS/2 computers are connected to a line-sharing device off of Router B. Each PS/2 computer has four sessions open on an AS/400 device attached to Router A. Router B functions as the primary station, while Router A functions as the secondary station. Both routers locally acknowledge packets from the IBM PS/2 systems.
Figure 83 STUN Communication Involving a Line-Sharing Device
The configuration file for the routers shown in follows.
Configuration for Router A
! enter the address of the stun peerstun peer-name 150.136.134.86! specify that group 4 uses the SDLC protocolstun protocol-group 4 sdlcstun remote-peer-keepaliveinterface ethernet 1! enter the IP address for the Ethernet interfaceip address 150.136.134.86 255.255.255.0!! description of IBM AS/400 linkinterface serial 2! description of IBM AS/400 link; disable the IP address on a serial interfaceno ip address! enable STUN encapsulation on this interfaceencapsulation stun! apply previously defined stun group 4 to serial interface 2stun group 4! establish this router as a secondary stationstun sdlc-role secondary! wait up to 63000 msec for a poll from the primary before timing outsdlc poll-wait-timeout 63000! list addresses of secondary stations (PS/2 systems) attached to linksdlc address C1sdlc address C2sdlc address C3sdlc address C4! use tcp encapsulation to send frames to SDLC stations C1, C2, C3, or! C4 and locally terminate sessions with these stationsstun route address C1 tcp 150.136.134.58 local-ackstun route address C2 tcp 150.136.134.58 local-ackstun route address C3 tcp 150.136.134.58 local-ackstun route address C4 tcp 150.136.134.58 local-ackConfiguration for Router B
! enter the address of the stun peerstun peer-name 150.136.134.58! this router is part of SDLC group 4stun protocol-group 4 sdlcstun remote-peer-keepalive!interface ethernet 1! enter the IP address for the Ethernet interfaceip address 150.136.134.58 255.255.255.0!! description of PS/2 linkinterface serial 4! disable the IP address on a serial interfaceno ip address! enable STUN encapsulation on this interfaceencapsulation stun! apply previously defined stun group 4 to serial interface 2stun group 4! establish this router as a primary stationstun sdlc-role primarysdlc line-speed 9600! wait 2000 milliseconds for a reply to a frame before resending itsdlc t1 2000! resend a frame up to four times if not acknowledgedsdlc n2 4! list addresses of secondary stations (PS/2 systems) attached to linksdlc address C1sdlc address C2sdlc address C3sdlc address C4! use tcp encapsulation to send frames to SDLC stations C1, C2, C3, or! C4 and locally terminate sessions with these stationsstun route address C3 tcp 150.136.134.86 local-ackstun route address C1 tcp 150.136.134.86 local-ackstun route address C4 tcp 150.136.134.86 local-ackstun route address C2 tcp 150.136.134.86 local-ack! set the clockrate on this interface to 9600 bits per secondclockrate 9600Configuring STUN Local Acknowledgment for SDLC Example
The following example shows a sample configuration for a pair of routers performing SDLC local acknowledgment.
Configuration for Router A
stun peer-name 150.136.64.92stun protocol-group 1 sdlcstun remote-peer-keepalive!interface Serial 0no ip addressencapsulation stunstun group 1stun sdlc-role secondarysdlc address C1stun route address C1 tcp 150.136.64.93 local-ackclockrate 19200Configuration for Router B
stun peer-name 150.136.64.93stun protocol-group 1 sdlcstun remote-peer-keepalive!interface Serial 0no ip addressencapsulation stunstun group 1stun sdlc-role primarysdlc line-speed 19200sdlc address C1stun route address C1 tcp 150.136.64.92 local-ackclockrate 19200Configuring STUN Local Acknowledgment for Frame Relay Example
The following example describes an interface configuration for Frame Relay STUN with local acknowledgment:
stun peer-name 10.1.21.1 cls 4stun protocol-group 120 sdlc!interface Serial1no ip addressencapsulation frame-relayframe-relay lmi-type ansiframe-relay map llc2 22!interface Serial4no ip addressencapsulation stunclockrate 9600stun group 120stun sdlc-role secondarysdlc address C1sdlc address C2stun route address C1 interface Serial1 dlci 22 04 local-ackstun route address C2 interface Serial1 dlci 22 08 local-ack!Configuring LOCADDR Priority Groups—Simple Example
The following example shows how to establish queuing priorities on a STUN interface based on an LU address:
! sample stun peer-name global commandstun peer-name 131.108.254.6! sample protocol-group command for referencestun protocol-group 1 sdlc!interface serial 0! disable the ip address for interface serial 0no ip address! enable the interface for STUNencapsulation stun! sample stun group commandstun group 2! sample stun route commandstun route address 10 tcp 131.108.254.8 local-ack priority!! assign priority group 1 to the input side of interface serial 0locaddr-priority 1priority-group 1!interface Ethernet 0! give locaddr-priority-list 1 a high priority for LU 02locaddr-priority-list 1 02 high! give locaddr-priority-list 1 a low priority for LU 05locaddr-priority-list 1 05 lowConfiguring LOCADDR Priority Groups for STUN Example
The following configuration example shows how to assign a priority group to an input interface:
Configuration for Router A
stun peer-name 1.0.0.1stun protocol-group 1 sdlc!interface serial 0no ip addressencapsulation stunstun group 1stun route address C1 tcp 1.0.0.2 local-ack priorityclockrate 19200locaddr-priority 1priority-group 1!interface Ethernet 0ip address 1.0.0.1 255.255.255.0!locaddr-priority-list 1 02 highlocaddr-priority-list 1 03 highlocaddr-priority-list 1 04 mediumlocaddr-priority-list 1 05 low!priority-list 1 protocol ip high tcp 1994priority-list 1 protocol ip medium tcp 1990priority-list 1 protocol ip normal tcp 1991priority-list 1 protocol ip low tcp 1992Configuration for Router B
stun peer-name 1.0.0.2stun protocol-group 1 sdlc!interface serial 0no ip addressencapsulation stunstun group 1stun route address C1 tcp 1.0.0.1 local-ack priorityclockrate 19200locaddr-priority 1priority-group 1!interface Ethernet 0ip address 1.0.0.2 255.255.255.0!locaddr-priority-list 1 02 highlocaddr-priority-list 1 03 highlocaddr-priority-list 1 04 mediumlocaddr-priority-list 1 05 low!priority-list 1 protocol ip high tcp 1994priority-list 1 protocol ip medium tcp 1990priority-list 1 protocol ip normal tcp 1991priority-list 1 protocol ip low tcp 1992Block Serial Tunneling (BSTUN)
Cisco's implementation of BSTUN provides the following features:
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BSC Network Overview
The BSC feature enables your Cisco 2500 series, Cisco 4000 series, or Cisco 4500 series router to support devices that use the Binary Synchronous Communication (BSC) data link protocol. This protocol enables enterprises to transport BSC traffic over the same network that supports their SNA and multiprotocol traffic, eliminating the need for separate bisync facilities.
At the access router, traffic from the attached BSC device is encapsulated in IP. The BSC traffic can then be routed across arbitrary media to the host site where another router supporting BSC will remove the IP encapsulation headers and present the BSC traffic to the BSC host or controller over a serial connection. HDLC can be used as an alternative encapsulation method for point-to-point links. shows how you can reconfigure an existing BSC link between two devices and provide the same logical link without any changes to the existing BSC devices.
Figure 84 Routers Consolidate BSC Traffic by Encapsulation in IP or HDLC
The routers transport all BSC blocks between the two devices in passthrough mode using BSTUN as encapsulation. BSTUN uses the same encapsulation architecture as STUN, but is implemented on an independent tunnel.
Point-to-Point and Multidrop Support
The BSC feature supports point-to-point, multidrop, and virtual multidrop BSC configurations.
Point-to-Point Operation
In point-to-point operation the BSC blocks between the two point-to-point devices are received and forwarded transparently by the Cisco IOS software. The contention to acquire the line for transmission is handled by the devices themselves.
Cisco's BSC multipoint operation is provided as a logical multipoint configuration. shows how a multipoint BSC link is reconfigured using Cisco routers. Router A is configured as BSC Secondary. It monitors the address field of the polling or selection block and uses this address information to put into the BSTUN frame for BSTUN to deliver to the correct destination router. To simulate the BSC multidrop, an EOT block is sent by the BSC Primary router before a poll or selection block. This ensures that BSC tributary stations are in control mode before being polled or selected.
Figure 85 Multipoint BSC Link Reconfigured Using Routers
Multidrop Configuration
Multidrop configurations are common in BSC networks where up to eight or ten BSC devices are frequently connected to a BSC controller port over a single low-speed link. Our virtual multidrop support allows BSC devices from different physical locations in the network to appear as a single multidrop line to the BSC host or controller. illustrates a multidrop BSC configuration before and after implementing routers.
Figure 86 Integrating BSC Devices over a Multiprotocol Network
Frame Sequencing
BSC is a half-duplex protocol. Each block of transmission is acknowledged explicitly. To avoid the problem associated with simultaneous transmission, there is an implicit role of primary and secondary station. The primary resends the last block if there is no response from the secondary within the period of block receive timeout. In the multidropsetup, the BSC control station is the primary and the tributary stations are secondary. In a point-to-point configuration, the primary role is assumed by the BSC device that has successfully acquired the line for transmission through the ENQ bidding sequence. The primary role stays with this station until it sends EOT.
To protect against occasional network latency, which causes the primary station to time out and resend the block before the BSC block sent by the secondary is received, the control byte of the encapsulating frame is used as a sequence number. This sequence number is controlled and monitored by the primary BSC router. This allows the primary BSC router to detect and discard "late" BSC blocks sent by the secondary router and ensure integrity of the BSC link.
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BSTUN Configuration Task List
The BSC feature is configured similar to SDLC STUN, but it is configured as a protocol within a BSTUN feature. To configure and monitor BSTUN, complete the tasks in the following sections:
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The "BSTUN Configuration Examples" section follows these tasks.
Enable Block Serial Tunneling
To enable BSTUN, perform the following task in global configuration mode:
Define the BSC Protocol Group
Define a BSTUN group and specify the protocol it uses. Currently the only block serial protocol supported is BSC. To define the BSC protocol group, perform the following task in global configuration mode:
Define the BSC protocol group.
bstun protocol-group group-number protocol [bsc | bsc-local-ack]
The bsc-local-ack protocol option only works for 3270 Bisync uses.
Enable BSTUN Keepalive
To define the number of times to attempt a peer connection before declaring the peer connection be down, perform the following task in global configuration mode::
Enable BSTUN Remote Keepalive
To enable detection of the loss of a peer, perform the following task in global configuration mode::
Configure BSTUN on the Serial Interface
Configure BSTUN on the serial interface before issuing any further BSTUN or BSC configuration commands for the interface. To configure the BSTUN function on a specified interface, perform the following command in interface configuration mode:
Place a Serial Interface in a BSTUN Group
Each BSTUN-enabled interface on a router must be placed in a previously defined BSTUN group. Packets will only travel between BSTUN-enabled interfaces that are in the same group. To assign a serial interface to a BSTUN group, perform the following task in interface configuration mode:
Define How Frames are Forwarded
To specify how frames are forwarded when received on a BSTUN interface, perform one of the following tasks in interface configuration mode:
Propagate all BSTUN traffic received on the input interface, regardless of the address contained in the serial frame. TCP encapsulation is used to propagate frames that match the entry.
bstun route all tcp ip-address1
Propagate all BSTUN traffic received on the input interface, regardless of the address contained in the serial frame. HDLC encapsulation is used to propagate the serial frames.
bstun route all interface serial number
Use HDLC encapsulation to propagate the serial frames. The specified interface is also a direct BSTUN link, rather than a serial connection to another peer.
bstun route interface serial number direct
Propagate the serial frame that contains a specific address. TCP encapsulation is used to propagate frames that match the entry.
bstun route address address-number tcp ip-address
Propagate the serial frame that contains a specific address. HDLC encapsulation is used to propagate the serial frames.
bstun route address address-number interface serial number
Propagate the serial frame that contains a specific address. HDLC encapsulation is used to propagate the serial frames. The specified interface is also a direct BSTUN link, rather than a serial connection to another peer.
bstun route address address-number interface serial number direct
1 This command functions in either passthrough or local acknowledgment mode.
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Set Up BSTUN Traffic Priorities
You can assign BSTUN traffic priorities based on either the BSTUN header or the TCP port. To prioritize traffic, perform one of the following tasks in global configuration mode:
You can customize BSTUN queuing priorities based on either the BSTUN header or TCP port. To customize priorities, perform one of the following tasks in global configuration mode:
Configure BSC Options on a Serial Interface
By default serial interfaces that are configured for bisynchronous tunneling run in half-duplex mode.To configure BSC options on a serial interface, perform one of the following tasks in interface configuration mode:
Specify the character set used by the BSC support feature.
bsc char-set [ascii | ebcdic]
Specify that the BSC link connected to the seial interface is a point-to-point BSC station.
bsc contention
Specify that the interface can run BSC using non-switched RTS signals in full-duplex mode.
full-duplex1
Specify the amount of time between the start of one polling cycle and the next.
bsc pause time
Specify the timeout for a poll or a select sequence.
bsc poll-timeout time
Specify that the router is acting as the primary end of the BSC link.
bsc primary
Specify the number of retries before a device is considered to have failed.
bsc retries retry-count
Specify that the router is acting as the secondary end of the BSC link.
bsc secondary
Specify specific polls, rather than general polls, used on the host-to-router connection.
bsc spec-poll
Specify the number of cycles of the active poll list that are performed between polls to control units in the inactive poll list.
bsc servlim servlim-count
1 This command is documented in the "Interface Commands" chapter of the Router Products Command Reference.
Monitor the Status of BSTUN
To list statistics regarding BSTUN interfaces, protocol groups, number of packets sent and received, local acknowledgment states, and other activity information, perform the following task in EXEC mode:
List the status display fields for BSTUN interfaces.
show bstun
Display status of the interfaces on which BSC is configured.
show bsc
BSTUN Configuration Examples
The following sections provide BSTUN configuration examples:
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Simple BSC Configuration Example
shows a simple BSTUN configuration example.
Figure 87 Simple BSC Configuration
The configuration files for the routers shown in follow.
Configuration for Router 45ka
version 10.2!hostname 45ka!no ip domain-lookup!bstun peer-name 150.10.254.201bstun protocol-group 1 bsc!interface ethernet 0ip address 198.92.0.201 255.255.255.0media-type 10BaseT!interface ethernet 1no ip addressshutdownmedia-type 10BaseT!interface serial 0no ip addressencapsulation bstunclockrate 19200bstun group 1bsc char-set ebcdicbsc secondarybstun route address C9 tcp 150.10.254.210bstun route address C8 tcp 150.10.254.210bstun route address C7 tcp 150.10.254.208bstun route address C6 tcp 150.10.254.208bstun route address C5 tcp 150.10.254.208bstun route address C4 tcp 150.10.254.208bstun route address C3 tcp 150.10.254.207bstun route address C2 tcp 150.10.254.207bstun route address C1 tcp 150.10.254.207bstun route address 40 tcp 150.10.254.207!interface serial 1no ip addressshutdown!interface serial 2no ip addressshutdown!interface serial 3no ip addressshutdown!interface tokenring 0no ip addressshutdown!interface tokenring 1ip address 150.10.254.201 255.255.255.0ring-speed 16!line con 0line aux 0line vty 0 4login!endConfiguration for Router 25ka
version 10.2!hostname 25ka!no ip domain-lookup!bstun peer-name 150.10.254.207bstun protocol-group 1 bsc!interface serial 0no ip addressshutdown!interface serial 1no ip addressencapsulation bstunclockrate 19200bstun group 1bsc char-set ebcdicbsc primarybstun route address C3 tcp 150.10.254.201bstun route address C2 tcp 150.10.254.201bstun route address C1 tcp 150.10.254.201bstun route address 40 tcp 150.10.254.201!interface tokenring 0ip address 150.10.254.207 255.255.255.0ring-speed 16!interface bri 0no ip addressshutdown!line con 0line aux 0line vty 0 4login!endConfiguration for Router 4kc
version 10.2!hostname 4kc!no ip domain-lookup!bstun peer-name 150.10.254.210bstun protocol-group 1 bsc!interface ethernet 0ip address 198.92.0.210 255.255.255.0media-type 10BaseT!interface serial 0no ip addressencapsulation bstunclockrate 19200bstun group 1bsc char-set ebcdicbsc primarybstun route address C9 tcp 150.10.254.201bstun route address C8 tcp 150.10.254.201!interface serial 1no ip addressshutdown!interface serial 2no ip addressshutdown!interface serial 3no ip addressshutdown!interface tokenring 0ip address 150.10.254.210 255.255.255.0ring-speed 16!interface tokenring 1no ip addressshutdown!line con 0line aux 0line vty 0 4login!endConfiguration for Router 25kb
version 10.2!hostname 25kb!no ip domain-lookup!bstun peer-name 150.10.254.208bstun protocol-group 1 bsc!interface serial 0no ip addressencapsulation bstunno keepaliveclockrate 19200bstun group 1bsc char-set ebcdicbsc primarybstun route address C7 tcp 150.10.254.201bstun route address C6 tcp 150.10.254.201bstun route address C5 tcp 150.10.254.201bstun route address C4 tcp 150.10.254.201!interface serial 1no ip addressshutdown!interface tokenring 0ip address 150.10.254.208 255.255.255.0ring-speed 16!!line con 0line aux 0line vty 0 4login!endPriority Queuing: Prioritization Based on BSTUN Header Example
In this example, the output interface examines header info and places packets with the BSTUN header on specified output queue.
priority-list 1 protocol bstun normalinterface serial 0priority-group 1interface serial 1encapsulation bstunbstun group 1bstun route all interface serial 0...or...bstun route address <bsc-addr> interface serial 0Priority Queuing: Prioritization Based on BSTUN Header and Packet Sizes Example
In this example, the output interface examines header information and packet size and places packets with the BSTUN header that match criteria (gt or lt specified packet size) on specified output queue.
priority-list 1 protocol bstun low gt 1500priority-list 1 protocol bstun hi lt 500interface serial 0priority-group 1interface serial 1encapsulation bstunbstun group 1bstun route all interface serial 0...or...bstun route address <bsc-addr> interface serial 0Priority Queuing: Prioritization Based on BSTUN Header and BSC Address Example
In this example, the output interface examines header information and BSC address and places packets with the BSTUN header that match BSC address on specified output queue.
priority-list 1 protocol bstun normaladdress <bstun-group> <bsc-addr>interface serial 0priority-group 1interface serial 1encapsulation bstunbstun group 1bstun route address <bsc-addr> interface serial 0Priority Queuing: Prioritization Based on BSTUN TCP Ports Example
In this example, the output interface examines TCP port number and places packets with the BSTUN port number (1976) on specified output queue.
priority-list 1 protocol ip high tcp 1976interface serial 0priority-group 1interface serial 1encapsulation bstunbstun group 1bstun route all tcp <bstun-peer-ip-addr>Priority Queuing: Prioritization Based on BSTUN TCP Ports and BSC Address Example
In this example, four TCP/IP sessions (high, medium, normal, and low) are established with BSTUN peers using BSTUN port numbers. The input interface examines the BSC address and uses the specified output queue definition to determine which BSTUN TCP session (high, medium, normal, or low) to use for sending the packet to the BSTUN peer.
The output interface examines TCP port number and places packets with the BSTUN port numbers on specified output queue.
priority-list 1 protocol ip high tcp 1976priority-list 1 protocol ip medium tcp 1977priority-list 1 protocol ip normal tcp 1978priority-list 1 protocol ip low tcp 1979!priority-list 1 protocol bstun <outputQ>address <bstun-group> <bsc-addr>!interface serial 0priority-group 1!interface serial 1encapsulation bstunbstun group 1bstun route address <bsc-addr> tcp <bstun-peer-ip-addr> prioritypriority-group 1Custom Queuing: Prioritization Based on BSTUN Header Example
In this example, the output interface examines header info and places packets with the BSTUN header on specified output queue.
queue-list 1 protocol bstun normal!interface serial 0custom-queue-list 1!interface serial 1encapsulation bstunbstun group 1bstun route all interface serial 0Custom Queuing: Prioritization Based on BSTUN Header and Packet Size Example
In this example, the output interface examines header information and packet size and places packets with the BSTUN header that match criteria (gt or lt specified packet size) on specified output queue.
queue-list 1 protocol bstun low gt 1500queue-list 1 protocol bstun high lt 500!interface serial 0custom-queue-list 1!interface serial 1encapsulation bstunbstun group 1bstun route all interface serial 0Custom Queuing: Prioritization Based on BSTUN Header and BSC Address Example
In this example the output interface examines header info _and_ BSC address and places packets with the BSTUN header that match BSC address on specified output queue.
queue-list 1 protocol bstun normaladdress <bstun-group> <bsc-addr>!interface serial 0custom-queue-list 1!interface serial 1encapsulation bstunbstun group 1bstun route address <bsc-addr> interface serial 0Custom Queuing: Prioritization Based on BSTUN TCP Ports Example
In this example, the output interface examines TCP port number and places packets with the BSTUN port number (1976) on specified output queue.
queue-list 1 protocol ip high tcp 1976!interface serial 0custom-queue-list 1!interface serial 1encapsulation bstunbstun group 1bstun route all tcp <bstun-peer-ip-addr>Custom Queuing: Prioritization Based on BSTUN TCP Ports and BSC Address Example
In this example, four TCP/IP sessions (high, medium, normal, and low) are established with BSTUN peers using BSTUN port numbers.
Input interface examines the BSC address and uses the specified output queue definition to determine which BSTUN TCP session (high, medium, normal, or low) to use.
Output interface examines TCP port number and places packets with the BSTUN port numbers on specified output queue.
For BSC addressing, output queues map as follows:
outputQ 1
Maps to medium BSTUN port (1977)
outputQ 2
Maps to normal BSTUN port (1978)
outputQ 3
Maps to low BSTUN port (1979
outputQ 4-10
Maps to high BSTUN port (1976)
queue-list 1 protocol ip high tcp 1976queue-list 1 protocol ip medium tcp 1977queue-list 1 protocol ip normal tcp 1978queue-list 1 protocol ip low tcp 1979!priority-list 1 protocol bstun normaladdress <bstun-group> <bsc-addr>!interface serial 0custom-queue-list 1!interface serial 1encapsulation bstunbstun group 1bstun route address <bsc-addr> tcp <bstun-peer-ip-addr> prioritycustom-queue-list 1
