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This chapter provides descriptions of the various ATM network interface types you can configure on the ATM switch router, along with their applications. An overview of the configuration for each type is also included.
This chapter includes the following sections:
Explicitly configuring interfaces is the alternative to ILMI autoconfiguration. You can accept the default ATM interface configuration or override it.
The example network shown in Figure 4-1 illustrates some standard ATM interface configurations. The subsequent sections of this chapter explain the various interface types shown here.
The network configuration in Figure 4-1 shows three campus buildings (finance, engineering, and headquarters) connected by an ATM backbone of private NNI links. A public UNI link using a VP tunnel connects through the WAN to a remote sales office.
The UNI specification defines communications between ATM end systems (such as workstations and routers) and ATM switches in private ATM networks. Figure 4-2 shows a private UNI interface between the ATM switch router (HB-1) in the headquarters building and a router with an ATM interface (HB-1) in the same building.
The UNI interface in Figure 4-2 has the following attributes:
 | Tips When connecting with non-Cisco equipment, you should verify that the UNI version is the same on both ends of a connection. Version negotiation can occasionally fail with nonstandard switches. |
Step 1 Disable autoconfiguration on the interface.
Because autoconfiguration negotiates the UNI parameters for the interface, this feature must be disabled before performing manual configuration.
Step 2 Configure the UNI side, type, and version on the interface.
The user side is the device with the ATM network interface, such as a router or workstation; the network side is the ATM switch. The type and version must be the same on both ends. For a description of the features supported in each of the UNI versions, see the "ATM Signaling ProtocolsUNI and NNI" section of the chapter "ATM Signaling and Addressing."
The Network-Network Interface (NNI) specification defines communications between two ATM switches in a private ATM network. Figure 4-3 shows a private NNI interface from the ATM switch router (HB-1) in the headquarters building to the ATM switch router (EB-1) in the engineering building.
The NNI interface in Figure 4-3 is a private one, because it connects devices within a private network. The concept of public and private NNIs is, however, useful only for description purposes. It is not a part of the actual configuration. Also, because NNI interfaces connect two ATM switches, both sides are network.
Step 1 Disable autoconfiguration on the interface.
Step 2 Specify the interface as NNI.
Step 3 Modify the maximum VPI bits configuration (optional).
The default VPI bit space for NNI interfaces is 8, which allows a maximum of 255 VPIs. You can increase the VPI bit space to 12, for a total of 4095 VPIs. See the "VPI/VCI Ranges for SVPs and SVCs" section in the chapter "Working with Virtual Connections."
Figure 4-4 shows an IISP between the ATM switch router (SB-1) in the remote sales office and the ATM switch router (SB-1) in the same office.
The IISP interface in Figure 4-4 has the following attributes:
Step 1 Disable autoconfiguration on the interface.
Step 2 Configure the interface as IISP and specify the UNI side and version.
Because there is no ILMI on IISP interfaces, these parameters must be manually configured. One interface is the user side, while the other is the network side. The versions should match on both devices.
Step 3 Configure the ATM route address prefix.
Specify the 13-byte address prefix of the destination interface for the static route.
For further information on IISP configuration, see "ATM Routing with IISP and PNNI."
Figure 4-5 shows a public UNI interface over a DS3 connection between the ATM switch router (HB-1) in the Headquarters building and the ATM switch router (SB-1) in the remote sales office. To support signaling across this connection, a VP tunnel must be configured.
Your ATM switch router supports three types of VP tunnels.
Configuring a VP tunnel for a single service category without traffic shaping requires the following steps:
Step 1 Configure the connection traffic table rows (optional).
The connection traffic table specifies traffic management parameters for a connection. See the "Connection Traffic Table" section in the chapter "Traffic and Resource Management."
Step 2 Configure a PVP on the interface.
Step 3 Create a tunnel using the VPI of the PVP.
The overall output of this VP tunnel is rate-limited by hardware to the peak cell rate (PCR) of the tunnel. This feature is useful and often necessary when sending traffic through a public network using leased bandwidth that might be policed by the service provider.
Shaped VP tunnels have the following restrictions:
Configuring a shaped VP tunnel requires the following steps:
Step 1 Configure a CBR connection traffic table row with the desired peak cell rate (PCR).
The connection traffic table is used to specify traffic management parameters for a connection. See the "Connection Traffic Table" section in the chapter "Traffic and Resource Management."
Step 2 Configure a PVP on the interface.
Step 3 Create a tunnel using the VPI of the PVP.
Hierarchical VP tunnels support the following service categories:
While capable of carrying any traffic category, a hierarchical VP tunnel is itself defined as CBR with a PCR.
Hierarchical VP tunnels have the following restrictions:
Configuring a hierarchical VP tunnel requires the following steps:
Step 1 Enable hierarchical mode globally and save the configuration.
Step 2 Reload the ATM switch router.
 | Caution When you reload the ATM switch router, all active connections are lost. |
Step 3 Configure the connection traffic table row with the desired CBR peak cell rate (PCR).
The connection traffic table specifies traffic management parameters for a connection. See the "Connection Traffic Table" section in the chapter "Traffic and Resource Management."
Step 4 Configure a PVP on the interface.
Step 5 Create a tunnel using the VPI of the PVP.
PVCs can be configured to transit a VP tunnel interface once the interface has been configured.
The following restrictions apply to an end point of a PVC-to-PVP tunnel subinterface:
Configuring a PVC to a VP tunnel is similar to configuring other cross-connections, and requires the following steps:
Step 1 Enter interface configuration mode for the interface you want to connect to the VP tunnel.
Step 2 Configure the PVC by associating its VPI and VCI values to the subinterface and VPI/VCI values for the VP tunnel.
A similar situation occurs when a virtual UNI is configured. For example, multiple VP tunnels traversing a VP switch might all carry signalling on VPI 0, VCI X. But these get remapped at the VP switch to, for example, VPI 1, VCI X. The end system expects VPI 0, VCI X, so the signaling request fails.
This problem is solved by specifying a signaling virtual path connection identifier (VPCI). The signaling VPCI specifies the value that is to be carried in the signaling messages within a VP tunnel. The connection identifier information element (IE) is used in signaling messages to identify the corresponding user information flow. The connection identifier IE contains the VPCI and VCI.
Configuring the signaling VPCI requires the following steps:
Step 1 Select the subinterface (VP tunnel) to configure and enter interface configuration mode.
Step 2 Specify a VPCI value.
Configuring the VPCI with a value of 0 works in most circumstances.
Posted: Mon Aug 16 14:05:09 PDT 1999
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