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We have a pair of routers connected via a 64kbps Point to Point Leased connection.

The WAN is running PPP on serial interfaces. The serial interfaces on either end of the links are attached to a Multilink interfaces for other purposes of (QoS/LFI)

The serial link was bearing a lot of CRC errors, hence we decided to implement PPP LQM as there was an alternate path available.

To start with, we implemented PPP LQM on the MLPPP interface, however after reading the RFC we came to know that PPP LQM is not supported on the logical Multilink interface

Then we removed the PPP LQM on the Multilink interface and directly configured the feature on the serial interface connected to the WAN 64kbps link

The command "ppp quality 96" was configured to enable the PPP LQM feature on both sides of the link

From that day onwards, we have been observing the following things

Line Protocol on both ends of the link on the serial interface keeps toggling every 30 seconds (i believe its gotta do with 3 keepalives of 10 seconds each)

This Line protocol fluctuation keeps happening throughout the day, even though, the link does not bear any errors (CRC/Input)

There are no increments in Carrier transistion or Interface resets on one end of the link

However the second end shows increments in Interface resets, however carrier transistions are constant

Although the Line protocol on the Serial interface at both ends keeps going UP & DOWN, the Mulitlink interface remains UP constantly without any toggle

When the bundle status using the command "show ppp multilink interface <multilink int nos>, was checked, the serial element is observed to be ACTIVE under the MLPPP bundle. However, the timer for which the Serial element is shown to be ACTIVE under the bundle keeps resetting every 30 seconds

As Multilink Interface remains UP despite Serial Line protocol fluctuations, the OSPF neighbor and the routes via this link remains UP constantly and creates a false source of route information

Please aid in resolving this issue. Also let me know if such instances have been observed with any other case in the past. Additionally, I hardly see any documentation on PPP LQM deployment on CCO site, please help in finding proper resources to the implementation for this feature.

thanks & regards


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