# Configuration Tasks

To configure a POS interface:

1. Configure a physical interface.
   host1(config)#interface pos 0/1
2. (Optional) Assign a text description or an alias to the interface.
   host1(config-if)#pos description austin01 pos interface
3. Configure the encapsulation method.
   host1(config-if)#encapsulation ppp
4. (Optional) Configure the internal clock source.
   host1(config-if)#clock source internal module
5. (Optional) Set the size of the CRC.
   host1(config-if)#crc 32
6. (Optional) Set the time interval at which the router calculates bit and packet rate counters.
   host1(config-if)#load-interval 90
7. (Optional) Set the type of loopback mode.
   host1(config-if)#loopback line
8. (Optional) Set the MRU size.
   host1(config-if)#mru 1000
9. (Optional) Set the MTU size.
   host1(config-if)#mtu 1000
10. (Optional) Set the type of framing.
    host1(config-if)#pos framing sdh
11. Disable payload scrambling.
    host1(config-if)#no pos scramble-atm
12. (Optional) Disable an interface.
    host1(config-if)#shutdown

clock source

- Use to set the clock source.
- You can set internal or line clocking.
- Internal clocking has two options:
  - module—Uses internal clock from the line module
  - chassis—Uses the configured router clock
- Example
  host1(config-if)#clock source internal module
- Use the no version to restore the default value, line.
- See clock source.

crc

- Use to set the number of bits used for CRC checking.
- CRC is an error-checking technique that uses a calculated numeric value to detect errors in transmitted data; 16 and 32 indicate the number of check digits per frame that are used to calculate the frame check sequence (FCS). Both the sender and receiver must use the same setting.
- Example
  host1(config-if)#crc 32
- Use the no version to restore the default value, 16.
- See crc.

encapsulation frame-relay ietf

- Use to specify Frame Relay as the encapsulation method for the interface.
- The router uses IETF format (RFC 2427 encapsulation).
- Example
  host1(config-if)#encapsulation frame-relay ietf
- Use the no version to remove the Frame Relay configuration from an interface.
- See encapsulation frame-relay ietf

encapsulation ppp

- Use to specify PPP as the encapsulation method for the interface.
- Example
  host1(config-if)#encapsulation ppp
- Use the no version to remove the PPP configuration from an interface.
- See encapsulation ppp.

interface pos

- Use to configure a POS interface.
- To specify a POS interface for ERX7xx models, ERX14xx models, and ERX310 router, use the slot/port[.subinterface ] format.
  - slot—Number of the chassis slot
  - port—Port number on the I/O module
  - subinterface—Number of the subinterface
- To specify a POS interface for E120 and E320 routers, use the slot/adapter/port format.
  - slot—Number of the chassis slot
  - adapter—Identifier for the IOA within the E320 chassis, either 0 or 1, where:
    - 0 indicates that the IOA is installed in the right IOA bay (E120 router) or the upper IOA bay (E320 router).
    - 1 indicates that the IOA is installed in the left IOA bay (E120 router) or the lower IOA bay (E320 router).
  - port—Port number on the IOA
- For more information about modules that support POS interfaces, see chapter Configuring Unchannelized OCx/STMx Interfaces in JunosE Physical Layer Configuration Guide.
- Examples
  host1(config-if)#interface pos 0/1 host1(config-if)#interface pos 5/0/0
- Use the no version to remove the POS interface.
- See interface pos.

load-interval

- Use to set the time interval at which the router calculates bit and packet rate counters.
- You can choose a multiple of 30 seconds, in the range 30–300 seconds.
- Example
  host1(config-if)#load-interval 90
- Use the no version to restore the default value, 300.
- See load-interval.

loopback

- Use to specify the type of loopback for a POS interface.
  - internal—Connects the local transmitted signal to the local received signal.
  - line—Connects the received network signal directly to the transmit network signal. When configured in line loopback mode, the router never receives data from the network.
- Example
  host1(config-if)#loopback line
- Use the no version to clear the loopback.
- See loopback.

mru

- Use to set the maximum allowable size of the MRU.
- Specify a value in the range 1–9996 bytes.
- Example
  host1(config-if)#mru 1000
- Use the no version to restore the default value, 4470.
- See mru.

mtu

- Use to set the maximum allowable size of the MTU.
- Specify a value in the range 1–9996 bytes.
- Example
  host1(config-if)#mtu 1000
- Use the no version to restore the default value, 4470.
- See mtu.

pos description

- Use to assign a text description or an alias to a POS HDLC interface.
- You can use this command to help you identify the interface and keep track of interface connections.
- The description or alias can be a maximum of 80 characters.
- Use show interfaces pos to display the text description.
- Example
  host1(config-if)#pos description austin01 pos interface
- Use the no version to remove the text description or alias.
- See pos description.

pos framing

- Use to set the type of framing for a POS interface.
  - sdh—Uses SDH framing format
  - sonet—Uses SONET framing format (the default)
- Example
  host1(config-if)#pos framing sdh
- Use the no version to restore the default value, sonet.
- See pos framing.

pos scramble-atm

- Use to enable payload scrambling on a POS interface.
- Payload scrambling is enabled by default. When enabled, both sides of the connection must be using the scrambling algorithm. The router uses a 43rd-order synchronous scrambler to scramble the output data.
- Example
  host1(config-if)#pos scramble-atm
- Use the no version to disable scrambling on the POS interface.
- See pos scramble-atm.

shutdown

- Use to disable a POS interface.
- Example
  host1(config-if)#shutdown
- Use the no version to restart a disabled interface.
- See shutdown.