Table Of Contents
MPLS Label Switch Controller Enhancements
MPLS LSC Functional Description
Using Controlled ATM Switch Ports as Router Interfaces
Typical ATM Hybrid Network with Virtual Trunks
General Redundancy Operational Modes
How LSC Redundancy Differs from Router and Switch Redundancy
How the LSC, ATM Switch, and VSI Work Together
Using LSC Redundancy in Dedicated LSC Mode
Using the MPLS LSC as a Label Edge Device
Using the Cisco 6400 Universal Access Concentrator as an MPLS LSC
Cisco 6400 UAC Architectural Overview
Control VC Setup for MPLS LSC Functions
Configuring the Cisco 6400 UAC To Perform Basic MPLS LSC Operations
Supporting ATM Forum Protocols
Platforms Supported by MPLS LSC
Supported Standards, MIBs, and RFCs
Configuring MPLS on the Primary 72xx Family LSC-Controlled BPX Port
Configuring MPLS on the Second 72xx Family LSC-Controlled BPX Port
Cisco 6400 UAC LSC Configuration
Configuring Cisco 6400 UAC NRP as an MPLS LSC
Configuring the Cisco 6400 UAC NSP for MPLS Connectivity to BPX
Verifying MPLS LSC Configuration
Configuration for BPX1 and BPX2
Configuration for BPX1 and BPX2
Configuring ATM-LSRs with a Cisco 6400 NRP Operating as LSC
Configuration for 6400 UAC NSP
Configuration for 6400 UAC NRP LSC1
Configuration for BPX1 and BPX2
Configuration for 6400 UAC NRP LSC2
Configuring ATM LSRs through ATM Network Using Cisco 7200 LSCs Implementing Virtual Trunking
Configuration for LSC1 Implementing Virtual Trunking
Configuration for BPX1 and BPX2
Configuration for LSC2 Implementing Virtual Trunking
Configuring ATM LSRs through ATM Network Using Cisco 6400 NRP LSCs Implementing Virtual Trunking
Configuration for 6400 UAC NSP
Configuration for 6400 UAC NRP LSC1 Implementing Virtual Trunking
Configuration for BPX1 and BPX2
Configuration for 6400 UAC NRP LSC2 Implementing Virtual Trunking
Configuring LSC Hot Redundancy
Configuration for BPX1 and BPX2
Configuration for Edge LSR 7200-1
Configuration for Edge LSR 7200-2
Configuring LSC Warm Standby Redundancy
Configuring an Interface Using Two VSI Partitions
show controllers vsi control-interface
show controllers vsi descriptor
show tag-switching atm-tdp bindings
show tag-switching atm-tdp bindwait
show xtagatm cos-bandwidth-allocation XTagATM
tag-switching atm disable-headend-vc
debug tag-switching xtagatm cross-connect
debug tag-switching xtagatm errors
debug tag-switching xtagatm events
debug tag-switching xtagatm vc
MPLS Label Switch Controller Enhancements
This document describes the Cisco Multiprotocol Label Switching (MPLS) Label Switch Controller (LSC). It describes the MPLS LSC, identifies the platforms supported by the MPLS LSC, provides configuration examples for MPLS LSC components, and describes related IOS command language interpreter (CLI) commands that can be used with the supported platforms.
This document includes the following major sections:
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Platforms Supported by MPLS LSC
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Feature Overview
The label switch controller (LSC), combined with the Cisco BPX 8650 IP+ATM switch, supports scalable integration of IP services over an ATM network. The MPLS LSC enables the Cisco BPX 8650 to:
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The MPLS LSC supports highly scalable integration of MPLS (IP+ATM) services by using a direct peer relationship between the Cisco BPX 8650 switch and MPLS routers. This direct peer relationship removes the limitation on the number of IP edge routers (typical of traditional IP-over-ATM networks), allowing service providers to meet growing demands for IP services. The MPLS LSC also supports direct and rapid implementation of advanced IP services over ATM networks using Cisco BPX 8650 switches.
MPLS combines the performance and virtual circuit capabilities of Layer 2 (data link layer) switching with the scalability of Layer 3 (network layer) routing capabilities. This combination enables service providers to deliver solutions for managing growth, providing differentiated services, and leveraging existing networking infrastructures.
The MPLS LSC architecture provides the flexibility to:
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By deploying the MPLS LSC across large enterprise networks or wide area networks, customers can:
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MPLS LSC Functional Description
The MPLS LSC is a label switch router (LSR) that is configured to control the operation of a separate ATM switch. Together, the MPLS LSC and the controlled ATM switch function as a single ATM MPLS router (ATM-LSR).
Figure 1 shows the functional relationship between the MPLS LSC and the ATM switch that it controls.
Figure 1 MPLS Label Switch Controller and Controlled ATM Switch
Referring to Figure 1, note that the following devices can function as an MPLS LSC:
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Note also from Figure 1 that a Cisco BPX 8600 Service Node (or a slave ATM device) can function as the controlled ATM switch.
The MPLS LSC controls the ATM switch by means of the Virtual Switch Interface (VSI), which runs over an ATM link connecting the two devices.
The dotted outline in Figure 1 represents the logical boundaries of the external interfaces of the MPLS LSC and the controlled ATM switch, as discovered by the IP routing topology. The controlled ATM switch provides one or more LC-ATM interfaces at this external boundary. The MPLS LSC can incorporate other label controlled or non-label controlled router interfaces.
MPLS LSC Benefits
By using the MPLS LSC, you can derive the following benefits:
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MPLS Terminology
Table 1 lists tag switching terms and the equivalent MPLS terms used in this document.
Using Controlled ATM Switch Ports as Router Interfaces
In the LSC, the LC-ATM ports on the controlled ATM switch are used as an IOS interface type called extended Label ATM (XTagATM). To associate these XTagATM interfaces with particular physical interfaces on the controlled ATM switch, use the interface configuration command extended-port.
Figure 2 shows a typical MPLS LSC configuration that controls three ATM ports on a Cisco BPX switch: ports 6.1, 6.2, and 12.2. These corresponding XTagATM interfaces were created on the MPLS LSC and associated with the corresponding ATM ports on the Cisco BPX switch by means of the extended-port command.
Figure 2 Typical MPLS LSC and BPX Configuration
Observe from Figure 2 that:
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Creating Virtual Trunks
Virtual trunks provide connectivity for Cisco WAN MPLS switches through an ATM cloud, as shown in Figure 3. Because several virtual trunks can be configured across a given physical trunk, virtual trunks provide a cost effective means of connecting across an entire ATM network. Each virtual trunk typically consumes only a part of the resources of the physical trunk.
The ATM equipment in the cloud must support virtual path switching and transmission of ATM cells based solely on the VPI in the ATM cell header. The virtual path identifier (VPI) is provided by the ATM cloud administrator (that is, by the Service Provider).
Typical ATM Hybrid Network with Virtual Trunks
Figure 3 shows three Cisco WAN MPLS switching networks, each connected to an ATM network by a physical line. The ATM network links all three of these subnetworks to every other subnetwork with a fully meshed network of virtual trunks. In this example, each physical interface is configured with two virtual trunks.
Figure 3 Typical ATM Hybrid Network Using Virtual Trunks
Benefits of Virtual Trunking
Virtual trunks provide the following benefits:
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Virtual Trunk Configuration
A virtual trunk number (slot number.port number.trunk number) differentiates the virtual trunks found within a physical trunk port. In Figure 4, three virtual trunks (4.1.1, 4.1.2, and 4.1.3) are configured on a physical trunk that connects to the port 4.1 interface of a BXM.
Figure 4 Virtual Trunks Configured on a Physical Trunk
These virtual trunks are mapped to the XtagATM interfaces on the LSC. On the XtagATM interface, you configure the respective VPI value using the command tag-switching atm vp-tunnel vpi. This VPI should match the VPI in the ATM network. The Label Virtual Circuits (LVCs) are generated inside this VP, and this VP carries the LVCs and their traffic across the network.
Virtual Trunk Bandwidth
The total bandwidth of all the virtual trunks on one port cannot exceed the maximum bandwidth of the port. Trunk loading (units of load) is maintained per virtual trunk, but the cumulative loading of all virtual trunks on a port is restricted by the transmit and receive rates for the port.
Virtual Trunk Features
The maximum number of virtual trunks that can be configured per card equals the number of virtual interfaces (VIs) on the BPX. The BXM supports 31 virtual interfaces; hence, it supports up to 31 virtual trunks. Accordingly, you can have interfaces starting from XtagATM411 to XtagATM4131 on the same physical interface.
Using LSC Redundancy
The following sections explain how LSC redundancy works:
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LSC Redundancy Architecture
LSC redundancy allows you to create a highly reliable IP network, one whose reliability is nearly equivalent to that provided by hot standby routing. Instead of using hot standby routing processes to create redundancy, this method uses a combination of LSCs, the Virtual Switch Interface (VSI), and IP routing paths with the same cost path for hot redundancy, or different costs for warm redundancy. The VSI allows multiple control planes (MPLS, PNNI, and voice) to control the same switch. Each control plane controls a different partition of the switch.
In the LSC redundancy model, two independent LSCs control the different partitions of the switch. Thus, two separate MPLS control planes set up connections on different partitions of the same switch. This is where LSC redundancy differs from hot standby redundancy. The LSCs do not need copies of each other's internal state to create redundancy. The LSCs control the partitions of the switch independently.
A single IP network consists of switches with one LSC (or a hot standby pair of LSCs) and MPLS edge label switch routers (LSRs).
If you change that network configuration by assigning two LSCs per switch, you form two separate MPLS control planes for the network. You logically create two independent parallel IP subnetworks linked at the edge.
If the two LSCs on each switch are assigned identical shares of the switch's resources and links, the two subnetworks are identical. You have two identical parallel IP subnetworks on virtually the same equipment, which would otherwise support only one network.
For example, Figure 5 shows a network of switches that each have two LSCs. MPLS Edge LSRs are located at the edge of the network, to form a single IP network. The LSCs on each switch have identical shares of the switch's resources and links, which makes the networks identical. In other words, there are two identical parallel IP subnetworks.
Figure 5 LSC Redundancy Model
Part of the redundancy model includes edge LSRs, which link the two networks at the edge.
If the network uses Open Shortest Path First (OSPF) or a similar IP routing protocol with an equal cost on each path, then there are at least two equally viable paths from every edge LSR to every other edge LSR. The OSPF equal cost multipath distributes traffic evenly on both paths. Therefore, MPLS sets up two identical sets of connections for the two MPLS control planes. IP traffic travels equally across the two sets of connections.
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With the LSC redundancy model, if one LSC on a switch fails, IP traffic uses the other path, without having to establish new links. LSC redundancy does not require the network to set up new connections when a controller fails. Because the connections to the other paths have already been established, the interruption to the traffic flow is negligible. The LSC redundancy model is as reliable as networks that use hot standby controllers. LSC redundancy requires hardware like that used by hot standby controllers. However, the controllers act independently, rather than in hot standby mode. For LSC redundancy to work, the hardware must have connection capacity for doubled-up connections.
If an LSC fails and LSC redundancy is not present, IP traffic halts until other switches break their present connections and reroute traffic around the failed controller. The stopped IP traffic results in undesirable unreliability.
General Redundancy Operational Modes
The LSC redundancy model allows you to use the following four operational models. Most other redundancy models cannot accommodate all of these redundancy models.
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How LSC Redundancy Differs from Router and Switch Redundancy
In traditional IP router networks, network managers ensure reliability by creating multiple paths through the network from every source to every destination. If a device or link on one path fails, IP traffic uses an alternate path to reach its destination.
Router Redundancy
Because routers do not need to establish a virtual circuit to transfer data, they are inherently connectionless. When a router discovers a failed device or link, it requires approximately less than a second to reroute traffic from one path to another.
Routers can incorporate a warm or hot standby routing process to increase reliability. The routing processes share information about the routes to direct different streams of IP traffic. They do not need to keep or share connection information. Routers can also include redundant switch fabrics, backplanes, power supplies, and other components to decrease the chances of node failures.
ATM, Frame Relay, and Circuit Switch Redundancy
Circuit switch, ATM, and Frame Relay networks transfer data by establishing circuits or virtual circuits. To ensure the transfer of data in switches, network managers incorporate redundant switch components. If any component fails, a spare component takes over. Switches can have redundant line cards, power supplies, fans, backplanes, switch fabrics, line cards, and control cards.
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A software application usually monitors the state of the switches and their components. If a problem arises, the software sets an alarm to bring attention to the faulty component.
The redundant switch hardware and software are required, because switches take some time to reroute traffic when a failure occurs. Switches can have connection routing software, such as Cisco automatic connection routing, PNNI, or MPLS. However, rerouting the connections in a switch takes much more time than rerouting traffic in a router network. Rerouting connections in a switch requires calculating routes and reprogramming some hardware for each connection. In router networks, large aggregates of traffic can be rerouted simultaneously, with little or no hardware programming. Therefore, router networks can reroute traffic more quickly and easily than connection oriented networks. Router networks rely on rerouting techniques to ensure reliability. Connection-oriented networks use rerouting only as a last resort.
General Hot/Warm Standby Redundancy in Switches
Network managers can install redundant copies of the connection routing software for ATM and Frame Relay switches on a redundant pair of control processors.
With hot standby redundancy, the active process sends its state to the spare process to keep the spare process up to date in case it needs to take over. The active process sends the state information to the spare process or writes the state to a disk, where both processes can access the information. In either case, the state information is shared between controllers. Because the state of the network routing tables changes frequently, the software must perform much work to maintain consistent routing states between redundant pairs of controllers.
With warm standby redundancy, the state information is not shared between the active and spare processes. If a failure occurs, the spare process resets all of the connections and re-establishes them. Reliability decreases when the spare resets the connections. The chance of losing data increases.
LSC Redundancy
Connecting two independent LSCs to each switch by the Virtual Switch Interface (VSI) creates two identical subnetworks. Multipath IP routing uses both subnetworks equally. Thus, both sub-networks have identical connections. If a controller in one subnetwork fails, the multipath IP routing diverts traffic to the other path. Because the connections already exist in the alternate path, the reroute time is very fast. The LSC redundancy model matches the reliability of networks with hot standby controllers, without the difficulty of implementing hot standby redundancy.
Benefits of LSC Redundancy
By implementing the LSC redundancy model, you eliminate the single point of failure between the LSC and the ATM switch it controls. If one LSC fails, the other LSC takes over and routes the data on the other path. The following sections explain the other benefits of LSC redundancy.
LSC Redundancy Does Not Use Shared States or Databases
In the LSC redundancy model, the LSCs do not share states or databases, which increases reliability. Sometimes, when states and databases are shared, an error in the state or database information can cause both controllers to fail simultaneously.
Also, new software features and enhancements do not affect LSC redundancy. Because the LSCs do not share states or database information, you do not have to worry about ensuring redundancy during every step of the update.
LSC Redundancy Allows Different Software Versions
The LSCs work independently and there is no interaction between the controllers. They do not share the controller's state or database, as other redundancy models require. Therefore, you can run different versions of the IOS software on the LSCs, which provides the following advantages:
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LSC Redundancy Allows Different Hardware
You can use different models of routers in this LSC redundancy model. Using different hardware in the redundancy model reduces the chance that a hardware fault would interrupt network traffic.
LSC Redundancy Allows You to Switch from Hot to Warm Redundancy on the Fly
You can implement hot or warm redundancy and switch from one model to the other. Hot redundancy can use redundant physical interfaces, slave ATM switches with Y redundancy, and redundant LSCs. This enables parallel paths and instant failover. If your resources are limited, you can implement warm redundancy, which uses only redundant LSCs. When one controller fails, the backup controller requires some reroute time. As your network grows, you can switch from hot to warm redundancy and back, without bringing down the entire network.
Other redundancy models require complex hardware and software configurations, which are difficult to alter when you change the network configuration. You must manually change the connection routing software from hot standby mode to warm standby mode.
LSC Redundancy Provides an Easy Migration from Standalone LSCs to Redundant LSCs
You can migrate from a standalone LSC to a redundant LSC and back again without affecting network operations. Because the LSCs work independently, you can add a redundant LSC without interrupting the other LSC.
LSC Redundancy Allows Configuration Changes in a Live Network
The hot LSC redundancy model provides two parallel, independent networks. Therefore, you can disable one LSC without affecting the other LSC. This feature has the following benefits:
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LSC Redundancy Provides Fast Reroute in IP+ATM Networks
The hot LSC redundancy model offers redundant paths for every destination. Therefore, reroute recovery is very fast. Other rerouting processes in IP+ATM networks require many steps and take more time.
In normal IP+ATM networks, the reroute process consists of the following steps:
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After this reroute process, the new path is ready to transfer data. Rerouting data using this process takes time.
The hot LSC redundancy method allows you to quickly reroute data in IP+ATM networks without using the normal reroute process. When you incorporate hot LSC redundancy, you create parallel paths. Every destination has at least one alternative path. If a device or link along the path fails, the data uses the other path to reach its destination. The hot LSC redundancy model provides the fastest reroute recovery time for IP+ATM networks.
How the LSC, ATM Switch, and VSI Work Together
In an LSC implementation, the LSC and slave ATM switch have the following characteristics:
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If a component on the LSC fails, the ATM switch's IP switching function is disabled. The standalone LSC is the single point of failure.
The VSI implementation includes the following characteristics:
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Implementing LSC Redundancy
To make an LSC redundant, you can partition the resources of the slave ATM switch, implement a parallel VSI model, assign redundant LSCs to each switch, and create redundant LSRs. The following sections explain each of these steps.
Partitioning the Resources of the ATM Switch
In the LSC redundancy model, two LSCs control different partitions of the ATM switch. When you partition the ATM switch for LSC redundancy, use the following guidelines:
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See the Cisco BPX 8600 Series documentation for more information about configuring the slave ATM switch.
Implementing the Parallel VSI Model
The parallel VSI model means that the physical interfaces on the ATM switch are shared by more than one LSC. For instance, LSC1 maps VSI slave interfaces 1 to N to the ATM switch's physical interfaces 1 to N. LSC2 maps VSI slave interfaces to the ATM switch's physical interfaces 1 to N. LSC1 and LSC2 share the same physical interfaces on the ATM switch. With this mapping, you achieve fully meshed independent masters.
Figure 6 shows four ATM physical interfaces mapped as four XtagATM interfaces at LSC1 and LSC2. Each LSC is not aware that the other LSC is mapped to the same interfaces. Both LSCs are active all the time. The ATM switch runs the same VSI protocol on both partitions.
Figure 6 XtagATM Interfaces
Adding Interface Redundancy
To ensure reliability throughout the LSC redundant network, you can also implement:
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Figure 7 Interface Redundancy
Implementing Hot or Warm LSC Redundancy
Virtually any configuration of switches and LSCs that provides hot redundancy can also provide warm redundancy. You can also switch from warm to hot redundancy with little or no change to the links, switch configurations, or partitions.
Hot and warm redundancy differ in the following ways:
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The following sections explain the two redundancy models in detail.
Implementing Hot LSC Redundancy
Hot redundancy provides instant failover to the other path when an LSC fails. When you set up hot redundancy, both LSCs are active and have the same routing costs on both paths. To ensure that the routing costs are the same, run the same routing protocols on the redundant LSCs.
In hot redundancy, the LSCs run parallel and independent Label Distribution Protocols (LDPs). At the edge LSRs, when the LDP has multiple routes for the same destination, it requests multiple labels. It also requests multiple labels when it needs to support Class of Service (CoS). When one LSC fails, the labels distributed by that LSC are removed.
To achieve hot redundancy, you can implement the following redundant components:
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Figure 8 shows one example of how hot LSC redundancy can be implemented.
Figure 8 Hot LSC Redundancy
Implementing Warm LSC Redundancy
To achieve warm redundancy, you need only redundant LSCs. You do not necessarily need to run the same routing protocols or distribution protocols on the LSCs.
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If you run the same routing protocols, you specify a higher cost for the interfaces on the backup LSC. This causes the data to use only the lower-cost path. This also saves resources on the ATM switch, because the edge LSR requests LVCs only through the lower-cost LSC. When the primary LSC fails, the edge LSR uses the backup LSC and creates new paths to the destination. Creating new paths requires reroute time and LDP negotiation time.
Figure 9 shows one example of how warm LSC redundancy can be implemented.
Figure 9 Warm LSC Redundancy
Using LSC Redundancy in Dedicated LSC Mode
Normally, LSCs include edge LSRs. In the "dedicated" LSC mode, the LSC removes edge LSR functionality. In Cisco 6400 NRP-based LSCs, the dedicated LSC mode of operation provides an opportunity for the LSC to be scaled. To achieve the edge LSR functionality, the LSC creates a label switch path (LSP) for each destination in the route table.
With LSC redundancy, if 400 destinations exist in the network, each redundant LSC adds 400 headend VCs. In hot redundancy mode, 800 headend VCs are created for the LSCs. If the LSCs are not edge LSRs, then 800 LVCs are wasted.
The number of LVCs increases as the number of redundant LSCs increases. In the case of a VC-merged system, the number of LVCs can be low. However, in non-VC-merged system, using the dedicated LSC mode is recommended.
Implementation Considerations
The following sections explain items that need to be considered when implementing hot or warm LSC redundancy in a network.
Hot LSC Redundancy Considerations
The following list explains the items you need to consider when implementing hot LSC redundancy:
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Warm LSC Redundancy Considerations
The following list explains the items you need to consider when implementing warm LSC redundancy:
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Using the MPLS LSC as a Label Edge Device
The MPLS LSC can perform as label edge device to:
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However, when the MPLS LSC acts as a label edge device, it is limited by the following factors:
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Using the Cisco 6400 Universal Access Concentrator as an MPLS LSC
You can configure the Cisco 6400 Universal Access Concentrator (UAC) to operate as an MPLS LSC in an MPLS network. The hardware that supports MPLS LSC functionality on the Cisco 6400 UAC is described in the following sections.
Cisco 6400 UAC Architectural Overview
A Cisco 6400 UAC can operate as an MPLS LSC if it incorporates the following components:
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The NRP contains internal ATM interfaces that enable it to be connected to the NSP. However, the NRP cannot directly access the external ATM interfaces of the Cisco 6400 UAC. Only the NSP can access the external ATM interfaces.
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Figure 10 shows the components that you can configure to enable the Cisco 6400 UAC to function as an MPLS LSC.
Figure 10 Cisco 6400 UAC Configured as an MPLS LSC
Configuring Permanent Virtual Circuits and Permanent Virtual Paths in Cisco 6400 UAC NSP Used as an MPLS NRP LSC
The NRP controls the slave ATM switch through the Virtual Switch Interface (VSI) protocol. VSI operates over a manually configured Permanent Virtual Circuit (PVC) that is dedicated to the virtual circuits (VCs) used by the VSI control channel. In order for the NRP LSC to control an ATM switch through the VSI, control VCs need to be cross-connected from the BPX through the NSP to the NRP LSC. The BPX uses defined control VCs for each BXM slot of the BPX chassis, enabling the LSC to control external XTagATM interfaces through the VSI.
Table 2 defines the PVCs that must be configured on the NSP interface connected to the BPX VSI shelf. These PVCs are cross-connected via the NSP to the NRP VSI master control port, which is running the VSI protocol.
For an NRP that is installed in slot 3 of a Cisco 6400 UAC chassis, the master control port would be ATM3/0/0 on the NSP. As shown in Figure 2, the BPX switch control interface is 12.1, and the NSP ATM port connected to this interface is the ATM interface that is cross-connected to ATM3/0/0. Because Figure 2 shows that the BXM slaves in BPX slots 6 and 12 are to be configured as external XTagATM ports, the PVCs that must be cross-connected through the NSP are 0/45 for slot 6 and 0/51 for slot 12, respectively, as outlined in Table 2.
Figure 11 shows the functional relationships among the Cisco 6400 UAC hardware components and the Permanent Virtual Paths (PVPs) that you can configure to support MPLS LSC functionality.
Figure 11 Cisco 6400 UAC PVP Configuration for MPLS LSC Functions
All other MPLS LSC functions, such as routing, terminating LVCs, and LDP control VCs (default 0/32), can be accomplished by means of a separate, manually configured PVP (see the upper shaded area in Figure 11). The value of "n" for this manually configured PVP must be the same among all the associated devices (the NRP, the NSP, and the slave ATM switch). Because the NSP uses VP=0 for ATM Forum signaling and the BPX uses VP=1 for autoroute, the value of "n" for this PVP for MPLS LSC functions must be greater than or equal to 2, while not exceeding an upper bound.
Note that some edge LSRs have ATM interfaces with limited VC space per virtual path (VP). For these interface types, you define several VPs. For example, the Cisco ATM Port Adapter (PA-A1) and the AIP interface are limited to VC range 33 through 1018. To use the full capacity of the ATM interface, configure four consecutive VPs. Make sure the VPs are within the configured range of the BPX.
For internodal BPX connections, it is suggested that you configure VPs 2 through 15; for edge LSRs, it is suggested that you configure VPs 2 through 5. (See the IOS CLI command "tag-switching atm vpi" on page 102 for examples of how to configure edge LSRs; see the BPX command "cnfrsrc" described in the Cisco BPX 8600 Series documentation for examples of how to configure BPX Service Nodes.)
Control VC Setup for MPLS LSC Functions
After you connect the NRP, the NSP, and the slave ATM switch by means of manually configured PVPs (as shown in Figure 11), the NRP can control the slave ATM switch as though it is directly connected to the NRP. The NRP discovers the interfaces of the slave ATM switch and establishes the default control VC to be used in creating MPLS VCs.
The slave ATM switch shown in Figure 11 incorporates two external ATM interfaces (labeled 1 and 2) that are known to the NRP as XTagATM61 and XTagATM122, respectively. On interface 6.1 of the slave ATM switch, VC 0/32 is connected to VC 2/35 by the VSI protocol. On the NRP, VC 2/35 is terminated on interface XTagATM61 and mapped to VC 0/32, also by means of the VSI protocol. This mapping enables the LDP to discover MPLS LSC neighbors by means of the default control VC 0/32 on the physical interface. On interface 12.2 of the slave ATM switch, VC 0/32 is connected to VC 2/83 by the VSI protocol. On the NRP, VC 2/83 is terminated on interface XTagATM122 and mapped to VC 0/32.
Note that the selection of these VCs is dependent on the availability of VC space. Hence it is not predictable what physical VC will be mapped to the external default control VC 0/32 on the XTagATM interface. The control VC will be shown as a PVC on the LSC, as opposed to a LVC, when you execute the IOS CLI command "show xtagatm vc" on page 95.
Configuring the Cisco 6400 UAC To Perform Basic MPLS LSC Operations
Figure 12 shows a Cisco 6400 UAC containing a single NRP that has been configured to perform basic MPLS LSC operations.
Figure 12 Typical Cisco 6400 UAC Configuration to Support MPLS LSC Functions
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ip address 192.103.210.5 255.255.255.255
Defining MPLS Control and IP Routing Paths
In the MPLS LSC topology shown in Figure 12, the devices labeled LSR1 and LSR2 are external to the Cisco 6400 UAC. These devices, with loopback addresses as their respective LDP identifiers, are connected to two separate interfaces labeled 6.1 and 12.2 on the slave ATM switch. Both LSR1 and LSR2 learn about each other's routes from the NRP by means of the data path represented as the thick dashed line in Figure 12. Subsequently, LVCs are established by means of LDP operations to create the data paths between LSR1 and LSR2 through the ATM slave switch.
Both LSR1 and LSR2 learn of the loopback address of the NRP and create a data path (LVCs) from each other that terminates in the NRP. These LVCs, called tailend LVCs, are not shown in Figure 12.
Disabling Edge LVCs
By default, the NRP requests LVCs for the next hop devices (the LSRs shown in Figure 12). These LVCs, called headend LVCs, enable the NRP/ATM slave switch combination to operate as an edge label switch router (edge LSR). Because the NRP is dedicated to slave ATM switch control by default, the headend LVCs are not required.
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The tag-switching atm disable-headend-vc CLI command disables the default behavior of the NRP in setting up headend switch LVCs, thereby saving VC space over the VP between the NRP and the slave ATM switch that the NRP controls. In the absence of additional LVCs, data traffic and control traffic use the same path.
Supporting ATM Forum Protocols
You can connect the MPLS LSC to a network that is running ATM Forum protocols while the MPLS LSC simultaneously performs its functions. However, you must connect the ATM Forum network through a separate ATM interface (that is, not through the master control port).
Platforms Supported by MPLS LSC
You can use the following platforms in conjunction with the MPLS LSC:
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Supported Standards, MIBs, and RFCs
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Configuration Tasks
This section provides examples of configuration tasks for enabling MPLS LSC functionality.
Refer to the Cisco BPX 8600 Series documentation for BPX Service Node configuration examples.
Configuring MPLS on the Primary 72xx Family LSC-Controlled BPX Port
Configuring MPLS on the Second 72xx Family LSC-Controlled BPX Port
Cisco 6400 UAC LSC Configuration
Configuring Cisco 6400 UAC NRP as an MPLS LSC
Guest
