Configuration of dual-link uplink backup

AR routers have two uplinks. If the two links both use the PPPoE dial-up method, the route backup method can be used to back up the two links. For example, the AR router has two dial-up interfaces: Dialer 1 and Dialer 2, and the active link and backup link can be determined by configuring the priority of static routes.

On field networks, when the PPPoE dial-up or authentication fails, or the IP address cannot be obtained, the router may need to automatically switch over to the backup route. However, the backup route takes over the active route only when the state of the Dialer1 interface changes to Down. In addition, a Dialer interface is a virtual logical interface, whose state is Snoofing Up. Therefore, the state of the Dialer1 interface cannot change to Down even if the PPPoE dial-up fails. A configuration scheme is described as follows to resolve this problem:

[Huawei] acl 3000 //Create the ACL list for NAT.
[Huawei-acl-adv-3000] rule permit ip //The list can be accessed by all users in general. The access can also be limited based on actual requirements.
[Huawei-acl-adv-3000] quit
[Huawei] interface dialer 1 //Create the virtual dial-up interface.
[Huawei-Dialer1] link-protocol ppp
[Huawei-Dialer1] ppp chap user 123456 //Username authenticated by CHAP
[Huawei-Dialer1] ppp chap password cipher huawei@123 //Password authenticated by CHAP
[Huawei-Dialer1] ppp pap local-user 123456 password cipher huawei@123 //Username and password authenticated by PAP
[Huawei-Dialer1] ip address ppp-negotiate //Obtain the IP address by PPP negotiation.
[Huawei-Dialer1] dialer user user1
[Huawei-Dialer1] dialer bundle 1 //Set the number of the Dialer bundle to 1.
[Huawei-Dialer1] dialer number 1 autodial //This command is added to ensure that the state of the Dialer interface changes to Down when the PPPoE dial-up fails.
[Huawei-Dialer1] dialer-group 1
[Huawei-Dialer1] nat outbound 3000 //NAT conversion list
[Huawei-Dialer1] quit
[Huawei] dialer-rule
[Huawei-dialer-rule] dialer-rule 1 ip permit
[Huawei-dialer-rule] quit
[Huawei] interface gigabitethernet 0/0/0 //Enter the view of the interface connecting to the operator.
[Huawei-GigabitEthernet0/0/0] pppoe-client dial-bundle-number 1 //Enable the PPPoE Client function and bind the PPPoE client to the created Dialer interface.
[Huawei-GigabitEthernet0/0/0] quit
[Huawei] ip route-static 0.0.0.0 0.0.0.0 dialer 1 preference 60 //Create the default route which directs to the Dialer1 interface, which indicates that when the active link is normal, the route to the external networks through the Dialer1 interface is used with higher priority.
[Huawei] ip route-static 0.0.0.0 0.0.0.0 dialer 2 preference 100 //When the active link is abnormal and the dial-up fails, the active link automatically switches over to the backup link which connects to the external networks through the Dialer2 interface.

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