Considerations for LDAP failover

For best results during active directory server failures the primary LDAP should also be the first nameserver in resolv.conf. Otherwise if the second active directory server goes down it could cause DNS resolution delays and slow down LDAP authentication.

Take note of your server hostnames and IP addresses. The hostnames and IPs in the table are for example only and are used in the following document examples.

LDAP server priority in Smile Hostname IP
Primary (ldap.url) DC.example.intranet 192.0.2.190
Secondary (ldap.secondary.url) DC2.example.intranet 192.0.2.195

The primary LDAP server IP should also be the first name server in resolv.conf.

/etc/resolv.conf

nameserver 192.0.2.190
nameserver 192.0.2.195

If using resolv.conf, also set the name servers in /etc/network/interfaces or they will be replaced on the next boot.

/etc/network/interfaces

iface eth0 inet static
        ...
        dns-nameservers 192.0.2.190 192.0.2.195