[Contents] [Prev] [Next] [Index] [Report an Error]

Configuring Data Link Layer Interfaces

You can configure the following data link layer interfaces:

Configuring IP/Frame Relay

The system supports IP over Frame Relay PVCs on the CT3, CT1, CE1, T3, and E3 modules. The interface presented to the incoming traffic is an IP/Frame Relay router. In addition, IP/PPP/Frame Relay is supported on the T3 and E3 modules. With this interface, the service provider can:

Figure 1-12 shows the structure of the system Frame Relay interface. Each system Frame Relay major interface sits on top of an HDLC interface. The Frame Relay implementation is divided into two levels: a major interface and one or more subinterfaces. This division allows a single physical interface to support multiple logical interfaces. Multiple IP interfaces can also be assigned to each Frame Relay major interface through the subinterfaces.


Figure 1-12 Frame Relay interface design

Figure 1-13 shows the structure of the Frame Relay protocols with the physical layer as the foundation. For Frame Relay, the physical layer can be CE1, E3, CT1, T3, or a fractional service, as supported by the different line module ports. The HDLC layer is on top of the physical layer and can support flexible assignment of physical resources.

For example, an HDLC channel can support one DS0, fractional T1s, or an entire T1. The major Frame Relay interface sits on top of the HDLC resource, and the subinterfaces sit on top of the major interface. The Frame Relay subinterfaces connect to the IP interface layer.


Figure 1-13 Structure of Frame Relay protocols

The system supports Frame Relay LMI (local management interface) to provide the operator with configuration and status information relating to the Frame Relay VCs in operation. LMI specifies a polling mechanism to receive incremental and full-status updates from the network. The system can represent either side of the User-to-Network Interface (UNI) and supports unidirectional LMI. Bidirectional support for Network-to-Network Interface (NNI) is also supported.

Figure 1-14 shows sample configuration parameters for Frame Relay on a serial interface.


Figure 1-14 Serial interface configuration parameters for a Frame Relay connection

The following sample command sequence configures a serial interface for Frame Relay. See ERX Link Layer Configuration Guide, Chapter 2, Configuring Frame Relay, for information.

host1(config-if)#interface serial 0/1:1/5

host1(config-if)#encapsulation frame-relay ietf

host1(config-if)#frame-relay intf-type dte

host1(config-if)#frame-relay lmi-type ansi

host1(config-if)#interface serial 0/1:1/5.1

host1(config-subif)#frame-relay interface-dlci 17 ietf

host1(config-subif)#ip address 192.32.10.2 255.255.255.0

Configuring IP/ATM

The system supports IP over ATM PVCs on the T3 ATM, E3 ATM, and OCx/STMx ATM line modules. This support allows service providers to receive traffic from subscribers who have CPE equipment, such as routers with ATM interfaces, to take in traffic from other network devices that use ATM, such as DSLAMs, and to connect to service providers with ATM backbone structures. See Figure 1-15.


Figure 1-15 ERX system IP/ATM access connection

Figure 1-16 shows the structure of the ATM interface. For ATM, this can be SONET, DS3, or E3 as supported by the different line modules. The major ATM interface sits on top of the SONET/DS3/E3 resource, and the subinterfaces sit on top of the major interface. The ATM subinterfaces connect to the IP interface layer.


Figure 1-16 Structure of the ATM interface design

Figure 1-17 shows the structure of the ATM protocols. The physical layer (SONET and/or DSx/Ex) is the foundation and provider of layer 1 framing service. The ATM layer is on top and provides cell, circuit, and OAM services. The AAL5 layer provides a frame-oriented interface to the ATM layer. The integrated local management interface (ILMI) provides local management across the UNI.


Figure 1-17 Structure of ATM protocol

Figure 1-18 shows sample configuration parameters for a typical ATM interface configuration.


Figure 1-18 ATM interface configuration parameters

The following sample command sequence configures an ATM interface on port 0 of the line module in slot 1. See ERX Link Layer Configuration Guide, Chapter 1, Configuring ATM, for information on how to configure an ATM interface.

host1(config)#interface atm 0/1 

host1(config-if)#interface atm 0/1.20

host1(config-if)#atm pvc 10 22 100 aal5snap

host1(config-subif)#ip address 192.32.10.20 255.255.255.0

Configuring IP/PPP

The system supports IP/PPP on the CT3, E1, and T3/E3 interfaces and IP/PPP/SONET on the OC3/STM1 and OC12/STM4 interfaces. This support allows service providers to accept traffic from subscribers who have CPE equipment, such as routers with PPP interfaces, and to transmit traffic in PPP format to other network devices.


Figure 1-19 The ERX system supports IP/PPP connections from the CPE

Figure 1-19 shows that the system supports the incoming IP/PPP traffic from the CPE. This traffic can then be routed to the uplink(s) attached to the system or to other CPEs that are attached to the system.

As shown in Figure 1-20, the PPP protocol can exist directly on top of the HDLC layer or on top of a layer 2 Frame Relay or ATM interface. In either case, IP rides on top of PPP, providing support for IP/PPP/ATM, IP/PPP/HDLC, and IP/PPP/Frame Relay. Both SONET and DSx/Ex interfaces are supported at the physical layer.


Figure 1-20 Structure of PPP    

Figure 1-21 shows sample configuration parameters for PPP on a serial interface.


Figure 1-21 ATM interface configuration parameters

The following sample command sequence configures PPP on a serial interface. See ERX Link Layer Configuration Guide, Chapter 4, Configuring Point-to-Point Protocol, for details.

host1(config)#interface serial 3/0:2/5

host1(config-if)#encapsulation ppp

host1(config-if)#ip address 192.32.22.10 255.255.255.0

Configuring IP/HDLC

The ERX system supports IP over Cisco HDLC on many types of serial interfaces. Cisco HDLC monitors line status on a serial interface by exchanging keepalive request messages with peer network devices. It also allows routers to discover IP addresses of neighbors by exchanging Serial Link Address Resolution Protocol (SLARP) address request and address response messages with peer network devices.

The system Cisco HDLC is compatible with Cisco Systems Cisco-HDLC protocol, the default protocol for all Cisco serial interfaces.

The system supports the following framing features:


Figure 1-22 Structure of Cisco HDLC protocol

As shown in Figure 1-22, the Cisco HDLC protocol can exist directly on top of the HDLC layer or ATM or SONET interface. Both SONET and DSx/Ex interfaces are supported at the physical layer.

Configuring IP over Ethernet

The ERX system supports IP/Ethernet. When you select an Ethernet interface, you can assign an IP address to it, as the following example shows:

host1(config)#interface fastethernet 4/1

host1(config-if)#ip address 192.5.127.8 255.255.255.0

Figure 1-23 shows the IP/Ethernet interface stack.


Figure 1-23 Example of IP over Ethernet stacking configuration steps
[Contents] [Prev] [Next] [Index] [Report an Error]