Enabling PPP link quality monitoring
PPP link quality monitoring (LQM) monitors the quality (packet loss ratio and packet error ratio) of PPP links (including those in MP bundles) in real time.
If PPP LQM is not enabled, each end of a PPP link periodically sends keepalives to its peer. If PPP LQM is enabled, Link Quality Reports (LQRs) packets replace keepalives to monitor the link.
The system uses received LQR packets to measure the link quality. If two consecutive measured results are below the close-percentage, the system shuts down the link. Then the system measures the link quality at an interval that is ten times the LQR interval. If three consecutive measured results are higher than the PPP LQM resume-percentage, the system brings up the link.
A shut-down link must experience a minimum of 30 keepalive intervals before it can come up again. As a best practice, do not set the keepalive interval to a large value.
If you enable PPP LQM on both sides of a PPP link, make sure both sides have the same PPP LQM settings. Typically, there is no need to enable PPP LQM on both sides of a PPP link.
As a best practice, do not enable PPP LQM on a DDR dial-up link because DDR tears the link down when the link is closed by LQM. Then LQM cannot send LQR packets to resume the link.
To enable PPP LQM:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Enable PPP LQM. | ppp lqm close-percentage close-percentage [ resume-percentage resume-percentage ] | By default, PPP LQM is disabled. |
4. Configure the interface to periodically send LCP echo packets when LQM detects a low quality link. | ppp lqm lcp-echo [ packet size ] [ interval interval ] | By default, the interface does not send LCP echo packets when LQM detects a low quality link. |