Switch support for Ethernet redundancy configuration example for LAN-to-LAN DLSw

As shown in Figure 84:

• DLSw operates in LAN-to-LAN mode.

• Configure DLSw on Router A, Router B, and Router C to connect the IBM host with the SNA host through the Internet.

1. Configure Router A:

   # Configure interfaces on Router A to make sure that the local DLSw peer 1.1.1.1 and remote peer 3.3.3.3 can reach each other. (Details not shown.)

   # Configure DLSw on Router A.

   <RouterA> system-view
   [RouterA] dlsw local 1.1.1.1
   [RouterA] dlsw remote 3.3.3.3
   

   # Enable DLSw Ethernet redundancy on interface Ethernet 1/0, and configure the multicast address as 9999-9999-9999 and set the priority to 10 for primary/secondary router election.

   [RouterA] interface ethernet 1/0
   [RouterA-Ethernet1/0] dlsw ethernet-backup enable 9999-9999-9999 priority 10
   

   # Enable switch support for DLSw Ethernet redundancy on interface Ethernet 1/0. Set the MAC address of the local device to 0500-0001-0000, the remote SNA device to 0200-0008-0080, and the device which will take over to perform MAC address mapping to 00f0-47b8-a5df when the current device is not available.

   [RouterA-Ethernet1/0] dlsw ethernet-backup map local-mac 0500-0001-0000 remote-mac 0200-0008-0080 neighbor 00f0-47b8-a5df
   

2. Configure Router B:

   # Configure interfaces on Router B to make sure that the local DLSw peer 2.2.2.2 and remote peer 3.3.3.3 can reach each other. (Details not shown.)

   # Configure DLSw on Router B.

   <RouterB> system-view
   [RouterB] dlsw local 2.2.2.2
   [RouterB] dlsw remote 3.3.3.3
   

   # Enable DLSw Ethernet redundancy on Ethernet 1/0, and configure the multicast address as 9999-9999-9999 for primary/secondary router election.

   [RouterB] interface ethernet 1/0
   [RouterB-Ethernet1/0] dlsw ethernet-backup enable 9999-9999-9999
   

   # Enable switch support for DLSw Ethernet redundancy on interface Ethernet 1/0. Set the MAC address of the local device to 0500-0201-0001, the remote SNA device to 0200-0008-0080, and the device which will take over to perform MAC address mapping to 00f0-47b8-a0dc when the current device is not available.

   [RouterB-Ethernet1/0] dlsw ethernet-backup map local-mac 0500-0201-0001 remote-mac 0200-0008-0080 neighbor 00f0-47b8-a0dc
   

3. Configure Router C:

   # Configure interfaces on Router C to make sure that the local DLSw peer 3.3.3.3 and remote peer 1.1.1.1 can reach each other. (Details not shown.)

   # Configure DLSw on Router C.

   <RouterC> system-view
   [RouterC] bridge enable
   [RouterC] bridge 5 enable
   [RouterC] dlsw local 3.3.3.3
   [RouterC] dlsw remote 1.1.1.1
   [RouterC] dlsw remote 2.2.2.2
   [RouterC] dlsw bridge-set 5
   [RouterC] interface ethernet 1/0
   [RouterC-Ethernet1/0] bridge-set 5
   

The Ethernet switch forwards frames through learning the source MAC addresses of Ethernet frames received on each port. In Figure 84, the Ethernet switch will receive the frames from the IBM host and forwarded by Router A and Router B, and these frames have the same source MAC address. As a result, the two interfaces of the Ethernet switch receive the same frame from the same host, and the spanning tree feature will block one of the two interfaces and cause circuit interruption.

If you configure the Ethernet switch to support DLSw Ethernet redundancy, when the router receives a frame from a WAN, the router replaces the source MAC address of the frame with the local MAC address. When the router receives a frame from an Ethernet, the router replaces the destination MAC address of the frame with the MAC address of the replaced remote SNA device. The one-to-one MAC address mapping solves the problem of the Ethernet switch mentioned above. Additionally, the DLSw Ethernet redundancy provides a backup router for the MAC address mapping function. The active router can deliver its own MAC address mapping rule to the backup router. The backup occurs between only the primary and secondary routers. The secondary router can deliver its MAC address mapping rule to the primary router, and the primary router can also deliver its own MAC address mapping rule to the secondary router. When the active router fails, the backup router takes over to perform MAC address mapping until the active router restores.