Using Ping to Monitor PW Connectivity on a VPWS Network

After you configure a virtual private wire service (VPWS) network, use pseudo wire (PW) ping to monitor PW connectivity on the VPWS network.

Prerequisites

Before testing pseudo wire (PW) connectivity using the ping vc command, ensure that the VPWS network has been configured correctly.

Context

To check whether a PW on the VPWS network is faulty, run the ping vc command. When the PW is Up, you can locate faults, such as forwarding entry loss or errors.

Table 1 describes check modes and usage scenarios.

**Table 1** Check modes and usage scenarios
Detection Mode	Usage Scenario	Description
Control-word	Supports Single-segment PW and multi-segment PW detection.	The MPLS echo request packet carries the control word between the PW label and the IP header. After the destination device receives the packet and finds that it carries the control word, the device sends the packet to the CPU for processing. This detection mode applies only when you enable the control-word on both ends of the PW.
Label-alert	Supports only Single-segment detection.	The MPLS echo request packet carries the label-alert tag between the PW label and the LSP label. After the destination device receives the packet and detects that it carries the label-alert tag, the device sends the packet to the CPU for processing. This detection mode applies only when you enable the label-alert for both ends of the PW.
TTL	Supports Single-segment and multi-segment PW detection.	A TTL specifies the expiration value. You must specify a TTL value to ensure that the TTL expires on the destination device so that the device sends the packet to the CPU for processing.

Procedure

Control-word mode:
To monitor PW connectivity using the control-word mode, run the ping vc vc-type pw-id [ peer-address ] [ -c echo-number | -m time-value | -s data-bytes | -t timeout-value | -exp exp-value | -r reply-mode | -v | -g] ^* control-word [ remote remote-ip-address peer-pw-id [ sender sender-address ] ] [ ttl ttl-value ] [ pipe | uniform ] [ bypass -si interface-name | interface-type interface-number ] command.

To monitor multi-segment PW connectivity, specify an IP address and a PW ID for the remote PE and a source IP address in the remote remote-ip-address peer-pw-id [ sender sender-address ] command.
Label-alert mode:
To monitor PW connectivity using the label-alert mode, run the ping vc vc-type pw-id [ peer-address ] [ -c echo-number | -m time-value | -s data-bytes | -t timeout-value | -exp exp-value | -r reply-mode | -v | -g ] ^* label-alert [ no-control-word ] [ bypass -si interface-name | interface-type interface-number ] command.
TTL mode:
To monitor PW connectivity using the TTL mode, run the ping vc vc-type pw-id [ peer-address ] [ -c echo-number | -m time-value | -s data-bytes | -t timeout-value | -exp exp-value | -r reply-mode | -v | -g ] ^* normal [ no-control-word ] [ remote remote-ip-address peer-pw-id ] [ ttl ttl-value ] [ pipe | uniform ] command.

To monitor multi-segment PW connectivity, specify an IP address and a PW ID for the remote PE and set a TTL value in the remote remote-ip-address peer-pw-id [ ttl ttl-value ] [ pipe | uniform ] command.

The ping vc command output contains the following information:
- Response to each ping VC packet: If no response packet is received after the corresponding timer expires, the message reading "Request time out" is displayed. If a response packet is received, the number of data bytes, packet sequence number, TTL, and response time are displayed.
- Final statistics: include the number of sent packets, number of received packets, percentage of sent packets with failed responses, and minimum, maximum, and average response times.
For example:
```
<HUAWEI> ping vc ethernet 100 control-word 
   PW PING : FEC 128 PSEUDOWIRE (NEW). Type = ethernet, ID = 100 : 100 data bytes, press CTRL_C to break
    Reply from 10.10.10.10: bytes=100 Sequence=1 time = 140 ms    
    Reply from 10.10.10.10: bytes=100 Sequence=2 time = 40 ms    
    Reply from 10.10.10.10: bytes=100 Sequence=3 time = 30 ms    
    Reply from 10.10.10.10: bytes=100 Sequence=4 time = 50 ms    
    Reply from 10.10.10.10: bytes=100 Sequence=5 time = 50 ms 
--- FEC: FEC 128 PSEUDOWIRE (NEW). Type = ethernet, ID = 100 ping statistics---

    5 packet(s) transmitted
    5 packet(s) received
    0.00% packet loss
    round-trip min/avg/max = 30/62/140 ms
```