Configuring PPP 373Configuring PPP LinkQuality ControlIntroduction to PPP link quality controlPPP link quality control (LQC) can monitor the real-time quality of PPP links(including those in MP bundles). A link goes down when its quality drops belowthe close percentage and goes up when its quality recovers above theresume-percentage. To avoid frequent flapping, a delay is involved before a link isreused.Before you enable PPP LQC, the PPP interface sends keepalives to the peer everysome time. After you enable LQC on the interface, it sends link quality reports(LQRs) instead of keepalives to monitor the link.When link quality is normal, the system calculates link quality based on each LQRand disables the link if the results of two consecutive calculations are below theclose-percentage. Once the link is disabled, the system starts to calculate linkquality every ten LQRs, and brings the link up if the results of three consecutivecalculations are higher than the resume-percentage. This means a disabled linkmust experience 30 keepalive periods before it can go up again. If a largekeepalive period is specified, it may take long time for the link to go up.Configuration procedureFollow these steps to configure PPP link quality control:Enabling the PPPAccounting StatisticsFunctionIntroduction to PPP accounting statisticsPPP can generate traffic-based accounting statistics on each PPP link. The statisticsinclude the amount of the inbound and outbound information (in terms of bytesand the number of the packets) on a link. The information can be used by AAAapplication modules for accounting and control purpose.ConfigureDNS addressnegotiationbased onactual needsEnable the local deviceto assign DNS serveraddress for the peerppp ipcp dnsprimary-dns-address[ secondary-dns-address]RequiredBy default, DNS serveraddress negotiation isdisabledEnable the device toaccept the DNS serveraddress assigned by thepeer or actively requestits peer for the DNSserver address (useeither of the two)ppp ipcp dnsadmit-anyRequiredBy default, DNS serveraddress negotiation isdisabled.ppp ipcp dns request RequiredBy default, a device isdisabled from requestingits peer for the DNSserver address actively.To do... Use the command... RemarksTo do... Use the command... RemarksEnter system view system-view -Enter the specifiedinterface viewinterface interface-typeinterface-number-Enable PPP LQC ppp lqc close-percentage[ resume-percentage ]RequiredBy default, resume-percentage isequal to close-percentage
