Configuration Options › Backbone LAN Parameters

Backbone LAN Parameters

The following parameters are usually the same for all grids in a single Backbone LAN. Unless the initial network setup found on the servers is incomplete, all of them have defaults and there is usually no need to override them. If necessary, set values for them in the default configuration file (/var/local/ald/defaults) so that they are applied to all new grid installations consistently.

ext_network

Specifies the external IP network (for example, 172.24.213.0/24). This value designates the "world-accessible" IP subnet to which the grid is connected. This parameter, together with the ext_gateway setting, is used to set the IP configuration of the controller.

For any of the following conditions, all addresses except those addresses in the "private networks" of the grid are routed through the gateway:

• This parameter is empty.
• The controller IP address does not belong to the specified range.

Default: Determined from the network configuration of the Distribution Server.

ext_vswitch

Specifies the name of the VSWITCH that provides access to the external IP network.

ext_gateway

Specifies the default gateway (for example, 172.24.213.1). All "world-routable" IP addresses outside the ext_network range are routed through this address. This parameter is typically set to the address of the WAN router that serves all hosts in the LAN. If the entire LAN is behind a NAT, this value can be a non-routable address (for example, 192.168.x.x). In all cases, the gateway is expected to provide access to the world.

Default: Determined from the network configuration of the Distribution Server.

ext_dns1, ext_dns2, and ext_dns3

Specify the DNS server IP addresses.

If no valid DNS servers are set up on the servers, providing at least ext_dns1 is mandatory.

Default: Determined from the network configuration of the Distribution Server.

legacy

Specifies whether to disable L2 switch identification. Setting this parameter to 1 disables L2 switch identification. If it is set to 0 (default), ALD takes the following actions:

• Listen for link-layer identification packets from the switches that are connected to each server.
• Use this information to determine the topology of connections between the servers.
• Configure the servers to use highly available redundant connections with two or more interfaces that are connected to each LAN.

Setting legacy=1 disables the capturing of switch identification packets and forces ALD to rely only on software-generated link-layer connectivity probes.

Note: Switch identification is beneficial even if there is no redundant wiring (each server has a single connection to each of the grid LANs.

Use legacy=1 only in the following low-performance setups:

• Both LANs (external and backbone) are connected to the same physical switch on different VLANs.
• The switch does not provide VLAN information in its link-layer ID packets.

legacy=1 can be set only for nonredundant setups ("legacy" mode). Setting this option when there are two parallel connections from any server to the same LAN causes an error, and the installation aborts.