Method for avoiding a loop in a network

A method for avoiding a loop in a network having more than two Virtual Private Network (VPN) sites, wherein each VPN site comprises at least two Edge Devices (EDs), the method being performed by an ED and comprising:

• interacting with other EDs in a same VPN site to elect a Designated Edge Device (DED);
• assigning an authorized forwarding instance to each ED in the same VPN site when the ED is elected as the DED;
• obtaining the authorized forwarding instance from the DED when the ED is not elected as the DED;
• allowing traffic of the authorized forwarding instance transmitted from or to a public network, and blocking traffic of unauthorized forwarding instance transmitted from or to the public network;
• periodically sending a message carrying a MAC address and/or priority of the ED;
• blocking traffic transmitted from or to the public network of all forwarding instances for a preset time period T1 when the message is not received from the DED for a preset time period T0;
• reelecting a new DED according to the MAC addresses and/or priorities of the EDs carried by the messages received from other EDs in the preset time period T1;
• assigning an authorized forwarding instance for each ED in the same VPN site when the ED is reelected as the DED;
• obtaining the authorized forwarding instance from the reelected DED;
• and
• updating the authorized forwarding instance when the authorized forwarding instance changes.

An edge device comprising:

• an electing module to interact with other EDs in a same VPN site to elect a DED;
• an assigning module to assign an authorized forwarding instance to each ED in the same VPN site when the ED is elected as the DED, wherein the assigning module is to, for each forwarding instance configured in each ED of the same VPN site, if the forwarding instance is configured only in one ED, assign the forwarding instance as the authorized forwarding instance to the one ED;
• if the forwarding instance is configured in at least two EDs, determine one of the at least two EDs according to an identity of the forwarding instance and the number of the EDs configured with the forwarding instance, and assign the forwarding instance as the authorized forwarding instance to the determined ED;
• an obtaining module to obtain the authorized forwarding instance from the DED when the ED is not elected as the DED;
• and
• a controlling module to allow traffic of the authorized forwarding instance transmitted from or to a public network, and block traffic of an unauthorized forwarding instance transmitted from or to the public network;
• and
• a processor to execute said electing module, said assigning module, said obtaining module, and said controlling module.