79[RouterA] domain bbb[RouterA-isp-bbb] authentication ppp hwtacacs-scheme hwtac[RouterA-isp-bbb] authorization ppp hwtacacs-scheme hwtac[RouterA-isp-bbb] accounting ppp hwtacacs-scheme hwtac[RouterA-isp-bbb] quit# Enable PPP encapsulation on Serial 2/1/0/1:0.[RouterA] interface serial 2/1/0/1:0[RouterA-Serial2/1/0/1:0] link-protocol ppp# Configure Serial 2/1/0/1:0 to authenticate the peer by using PAP in authentication domainbbb.[RouterA-Serial2/1/0/1:0] ppp authentication-mode pap domain bbb3. Configure Router B:# Configure IP addresses for interfaces. (Details not shown.)# Enable PPP encapsulation on Serial 2/1/0/1:0. system-view[RouterB] interface serial 2/1/0/1:0[RouterB-Serial2/1/0/1:0] link-protocol ppp# Configure the local username and password for PAP authentication to userb and plaintextpassb, respectively.[RouterB-Serial2/1/0/1:0] ppp pap local-user userb password simple passbVerifying the configuration# Use the display interface serial command to display information for Serial 2/1/0/1:0. The PPP linkis established if the output contains the following information:• Both the physical layer and link layer are up.• LCP and IPCP have entered the Opened state.Router A and Router B can ping each other.Troubleshooting RADIUSRADIUS authentication failureSymptomUser authentication always fails.AnalysisPossible reasons include:• A communication failure exists between the NAS and the RADIUS server.• The username is not in the userid@isp-name format, or the ISP domain is not correctlyconfigured on the NAS.• The user is not configured on the RADIUS server.• The password entered by the user is incorrect.• The RADIUS server and the NAS are configured with different shared keys.SolutionTo resolve the problem:1. Verify the following items:
