Making network interfaces match

Matching interfaces

Each filer in a cluster must be configured in such a way that if one filer fails, the other can take over its IP and MAC (media access control) addresses. Each filer must meet the following requirements:

Each filer must be attached to the same networks and subnetworks as its partner.
Each local interface must have a local address and a partner address; that is, each must have an address on the partner that the partner can use if it takes over the local filer.

In general, it is a good idea to have pairs of addresses, where local and partner addresses reflect each other. For example, address n.n.n.n is the local address for interface x on Filer 1 and the partner address on Filer 2, address m.m.m.m is the local address for interface x on Filer 2 and the partner address on Filer 1, and both addresses are on the same subnetwork. This ensures that a filer's partner can provide the same services that the filer can.

Types of interfaces

On a filer in a cluster, interfaces can play three roles, as described in the following table.


Role	Description	Has local IP address?	Has partner IP address?
Dedicated network interface	Connects only the local filer. That is, if the partner filer fails, it is not available to the partner.	Yes	No
Shared network interface	Connects both the local filer and the partner. That is, if the partner fails, the network interface assumes the identity of a network interface on the partner but works on behalf of both the takeover filer and the partner.	Yes	Yes
Standby network interface	Connects only the partner. That is, if the partner fails, the network interface works on behalf of the partner. When the filer is not in takeover mode, the network interface is idle.	No	Yes

In addition to assuming the partner IP address in takeover mode, a shared or standby interface assumes the MAC address of the partner. This enables the clients of the partner to continue using their address resolution protocol (ARP) tables after the takeover.

Configuring interfaces

You configure an interface using setup as described in the First-Time Configuration Guide, or manually using the ifconfig command.

Note: The partner netmask is inferred from the partner IP address.

Using setup

During setup, the following questions appear for each interface:

Please enter IP address for Network Interface ns0 [n.n.n.n]:

Please enter netmask [255.255.0.0]:

Should interface ns0 take over a partner IP address during 
failover? [y]:

Please enter the IP address to take over: [m.m.m.m]:

Substitute the local address for n.n.n.n and the partner address for m.m.m.m.

Using ifconfig

How you use the ifconfig command depends on whether you are configuring a shared network interface or are configuring a standby interface for takeover:

To configure a dedicated network interface, put the following command in the filer's /etc/rc file:
```
ifconfig e0 local_IP_address
```
To configure a shared network interface, put the following command in the filer's /etc/rc file:
```
ifconfig e0 local_IP_address partner partner_IP_address
```
To configure a separate interface to be used only if the local filer is taken over, put the following command in the filer's /etc/rc file:
```
ifconfig e0 partner partner_IP_address
```

The Data ONTAP 5.2 System Administrator's Guide provides more information on using the ifconfig command.

Dual-MAC address cards

The following types of network interface cards that support dual-MAC addresses are supported:

Single-port 10/100 Base-T Ethernet
Quad-port 10/100 Base-T Ethernet
FDDI

The Data ONTAP 5.2 System Administrator's Guide provides more information about the types of network interface cards that support dual-MAC addresses.

Part No. 210-02327
File: cf_set2.htm
Last updated: 02/22/99 13:19:03