3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 2 Configuration of L2TP3Com Corporation2-20Operation CommandRestore the default value of Hellointerval. undo tunnel timer helloBy default, Hello interval is 60 seconds. If this configuration is not performed on LNSside, LNS will adopt this default value to send Hello packet to the peer end periodically.2.3.9 Enabling Mandatory Local CHAP AuthenticationAfter LAC performs agent authentication on a user, LNS can authenticate the useragain. The user therefore undergoes authentication twice: once on LAC side and onceon LNS side. Only after both the two authentications succeed, can L2TP tunnel becreated.In an L2TP network, LNS side authenticates users in three ways: agent authentication,mandatory CHAP authentication, and LCP re-negotiation.Among these three authentication approaches, LCP re-negotiation is of the first priority.If both LCP re-negotiation and mandatory CHAP authentication are configured on LNSside, L2TP will choose the former, adopting the authentication mode configured in theassociated virtual template.If only CHAP authentication is configured, LNS will perform CHAP authentication onusers.To perform mandatory CHAP authentication on LNS side, you must configureusername, password and user authentication and enable AAA on this side. Mandatorylocal CHAP authentication is optional on LNS side.Perform the following configuration in L2TP group view.Table 2-27 Enable mandatory local CHAP authenticationOperation CommandEnable mandatory local CHAP authentication. mandatory-chapDisable local CHAP authentication. undo mandatory-chapWhen LNS adopts agent authentication (that is, neither LCP re-negotiation normandatory CHAP authentication is configured), the following applies: If noauthentication mode is configured in the virtual template, LAC sends to LNS allauthentication information received from the user as well as authentication modeconfigured on LAC side, and LNS side will accept the authentication result on LAC side.When LNS adopts agent authentication, the following applies: If the authenticationmode configured in the virtual template is PAP and the authentication is successful,sessions are permitted to be established. If the authentication mode configured in the
