Specifications

Configure a Packet OC-3 Interface
Configuring Serial Interfaces IC-97
Configure a Packet OC-3 Interface
The Cisco Packet OC-3 Interface Processor (POSIP) and Packet OC-3 Port Adapter (POSPA) are
available on Cisco 7200 and Cisco 7500 series routers.
The POS is a fixed-configuration interface processor that uses second-generation Versatile Interface
Processor (VIP2) technology. The POS provides a single 155.520-Mbps, OC-3 physical layer
interface for packet-based traffic. This OC-3 interface is fully compatible with SONET and
Synchronous Digital Hierarchy (SDH) network facilities and is compliant with RFC 1619, “PPP
over SONET/SDH,” and RFC 1662, “PPP in HDLC-like Framing.” The Packet-Over-SONET
specification is primarily concerned with the use of the PPP encapsulation over SONET/SDH links.
Table 9 describes the default values set in the initial configuration of a Packet OC-3 interface.
Table 9 Packet OC-3 Interface Default Configuration
Because the Packet OC-3 interface is partially configured, you might not need to change its
configuration before enabling it. However, when the router is powered up, a new Packet OC-3
interface is shut down. To enable the Packet OC-3 interface, you must use the no shutdown
command in the global configuration mode.
Packet OC-3 Interface Configuration Task List
The values of all Packet OC-3 configuration parameters can be changed to match your network
environment. Perform the optional tasks in the following sections if you need to customize the POS
configuration:
• Select a Packet OC-3 Interface
• Set the MTU Size
• Configure Framing
• Configure an Interface for Internal Loopback
• Configure an Interface for Line Loopback
• Set the Source of the Transmit Clock
• Enable Payload Scrambling
• Configure an Alarm Indication Signal
Attributes Default Value
Maximum transmission unit
(MTU)
4470 bytes
Framing SONET STS-3c framing
Loopback internal No internal loopback
Loopback line No line loopback
Transmit clocking Recovered receive clock
Enabling Shut down