NE20Es Functioning as BRASs

On the network shown in Figure 8-10, NE20E-1 and NE20E-2 function as BRASs and run redundancy user information (RUI). A Virtual Router Redundancy Protocol (VRRP) backup group is configured for the two NE20Es, with NE20E-1 as the master and NE20E-2 as the backup. When the link between the switch (SW) and NE20E-1 goes faulty, the fault triggers a master/backup VRRP switchover. Then, NE20E-2 becomes the master and starts neighbor discovery (ND) detection, and NE20E-1 becomes the backup and stops the ND detection. If the link-local address or MAC address on an interface of NE20E-2 is different from that of an interface on NE20E-1, some users will go offline, or some user packets will be discarded.

To prevent a user from detecting the active link fault, NE20E-2 must use the same link-local address and MAC address as those of NE20E-1.

• Link-local address generation

  When an NE20E sends ND packets, its source IP address must be filled with a link-local address.

  After RUI is enabled on the NE20Es, the master and backup BRASs generate the same link-local address using the virtual MAC address of the VRRP backup group. The link-local address is generated automatically, which is convenient for users.

• Protection tunnel forwarding

  An address pool backup allows the master and backup BRASs to have the same MAC address. Address pool backup in IPv6 unicast forwarding control is similar to that in IPv4 unicast forwarding control. For details, see chapter IPv4 Unicast Forwarding Control

  IPv6 unicast forwarding allows the NE20Es to control traffic through multiprotocol label switching (MPLS) label switched paths (LSPs) and supports simplified protection tunnel configuration, requiring only MPLS LSPs for virtual private networks (VPNs). Each VPN swaps its forwarding labels using a Huawei-proprietary protocol, avoiding the need to configure the Border Gateway Protocol (BGP) on the NE20Es.

NE20Es Functioning as DHCPv6 Servers

Additionally, an NE20E can function as a DHCPv6 server or relay agent in IPv6 unicast forwarding control.

On the network shown in Figure 8-11, the NE20Es act as the master and backup DHCPv6 servers by running VRRP. The master DHCPv6 server assigns an IPv6 address to the PC. The DHCPv6 packets that the master DHCPv6 server sends carry the DHCP unique identifier (DUID), which uniquely identifies the DHCPv6 server. If RUI is enabled for the two DHCPv6 servers, to ensure that the new master DHCPv6 server sends correct DHCPv6 packets to the PC after a master/backup switchover, the master and backup DHCPv6 servers must use the same DUID.

The PC automatically generates a DUID in the link-layer address (DUID-LL) mode using the virtual MAC address of the VRRP backup group. This process avoids the need to configure a DUID in the link-layer address plus time (DUID-LLT) mode or configure a DUID statically.

After the DUID is generated in the DUID-LL mode, the master and backup DHCPv6 servers do not use the globally configured DUID, saving the process of backing up the DUID between the servers.

NE20Es Functioning as DHCPv6 Relay Agents

On the network shown in Figure 8-12, the NE20Es act as the master and backup DHCPv6 relay agents. A unique DHCPv6 relay agent remote-ID identifies the master DHCPv6 relay agent. In the RUI-enabled scenario, to enable the backup DHCPv6 relay agent to forward the DHCPv6 packets after a master/backup switchover, the master and backup DHCPv6 relay agents must use the same DHCPv6 relay agent remote-ID. This way ensures that the DHCPv6 server processes the packets correctly.

The RUI-enabled PC uses the DUID that identifies the master and backup DHCPv6 servers as the DHCPv6 relay agent remote-ID to identify both the master and backup DHCPv6 relay agents.