You can configure multiple IP addresses and enable anycast addressing on the loopback interface of the NIOS appliance, allowing the appliance to function in different network deployments.
Configuring non-anycast IP addresses on the loopback interface assists in server migration and network address change. Configuring anycast addresses on the appliance allows you to add redundancy and improve reliability for DNS services. You can use OSPF (Open Shortest Path First), BGP (Border Gateway Protocol), or both, as the routing protocol for anycast advertising.
This chapter contains the following sections:

• Using the Loopback Interface
• Configuring IP Addresses on the Loopback Interface
  • Advertising Loopback Addresses to the Network
• About Anycast Addressing for DNS
• Configuring Anycast Addresses
• Best Practices for Configuring Anycast Addresses
• IP Routing Options
  • About OSPF
  • Anycast and OSPF
  • Configuring OSPF on the NIOS Appliance
  • Anycast and BGP4
  • Configuring BGP in the NIOS Appliance
• About BFD (Bidirectional Forwarding Detection)
  • Enabling BFD for OSPF
  • Enabling BFD for BGP Neighbor
  • Creating a BFD Template
  • Enabling and Disabling DNS Health Check Monitor
  • Monitoring with SNMP

Using the Loopback Interface

The loopback interface is a virtual network interface on the appliance. You can do the following on the loopback interface:

• Configure IP addresses to consolidate DNS servers for migration purposes. For information, see Configuring IP Addresses on the Loopback Interface.
• Add anycast addresses to improve the reliability and performance of DNS services in multiple locations. For information, see About Anycast Addressing for DNS.
• Separate DNS traffic by assigning an IP address as the source port for DNS queries. For information, see Specifying Source Ports.

When you use the loopback interface for anycast addressing, the upstream and neighboring routers can continue to advertise anycast addresses without being affected by hardware malfunctions.
To configure non-anycast addresses on the loopback interface, complete the following:

1. Add IP addresses to the loopback interface. For information, see Configuring IP Addresses on the Loopback Interface .
2. Enable DNS services on the loopback addresses. For information, see Specifying Port Settings for DNS and its subtopic, Specifying Source Ports.

To configure DNS anycast addresses and their advertising protocols, complete the following:

1. Add anycast addresses to the loopback interface. For information, see Configuring Anycast Addresses.
2. Configure anycast addressing protocols. For information, see Configuring OSPF on the NIOS Appliance and Configuring BGP in the NIOS Appliance. This is the primary application for routing protocols in the NIOS appliance.
3. Enable the DNS anycast addresses. For information, see Specifying Port Settings for DNS and its subtopic, Specifying Source Ports.

To separate DNS queries from DNS transfers and notify messages, complete the following:

1. Add an IP address of the source port for DNS queries. For information, see Configuring IP Addresses on the Loopback Interface.
2. Select the source IP for DNS queries. For information, see Specifying Source Ports.