Use Case 2: ISP Tenant Uses DNS Proxy to Handle DNS Resolution for Security Policies, Reporting, and Services within its Virtual System

In this use case, multiple tenants (ISP subscribers) are defined on the firewall and each tenant is allocated a separate virtual system (vsys) and virtual router in order to segment its services and administrative domains. The following figure illustrates several virtual systems within a firewall.

Each tenant has its own server profiles for Security policy rules, reporting, and management services (such as email, Kerberos, SNMP, syslog, and more) defined in its own networks.

For the DNS resolutions initiated by these services, each virtual system is configured with its own DNS Proxy Object to allow each tenant to customize how DNS resolution is handled within its virtual system. Any service with a Location will use the DNS Proxy object configured for the virtual system to determine the primary (or secondary) DNS server to resolve FQDNs, as illustrated in the following figure.

1. For each virtual system, specify the DNS Proxy to use.
   1. Select DeviceVirtual Systems and Add the ID of the virtual system (range is 1-255), and an optional Name, in this example, Corp1 Corporation.
   2. On the General tab, choose a DNS Proxy or create a new one. In this example, Corp1 DNS Proxy is selected as the proxy for Corp1 Corporation’s virtual system.
   3. For Interfaces, click Add. In this example, Ethernet1/20 is dedicated to this tenant.
   4. For Virtual Routers, click Add. A virtual router named Corp1 VR is assigned to the virtual system in order to separate routing functions.
   5. Click OK.
2. Configure a DNS Proxy and a server profile to support DNS resolution for a virtual system.
   1. Select NetworkDNS Proxy and click Add.
   2. Click Enable and enter a Name for the DNS Proxy.
   3. For Location, select the virtual system of the tenant, in this example, Corp1 Corporation (vsys6). (You could choose the Shared DNS Proxy resource instead.)
   4. For Server Profile, choose or create a profile to customize DNS servers to use for DNS resolutions for this tenant’s security policy, reporting, and server profile services.
      If the profile is not already configured, in the Server Profile field, click DNS Server Profile to Configure a DNS Server Profile.

      The DNS server profile identifies the IP addresses of the primary and secondary DNS server to use for management DNS resolutions for this virtual system.
   5. Also for this server profile, optionally configure a Service Route IPv4 and/or a Service Route IPv6 to instruct the firewall which Source Interface to use in its DNS requests. If that interface has more than one IP address, configure the Source Address also.
   6. Select the Advanced tab. Ensure that Cache is enabled and Cache EDNS Responses is enabled (both are enabled by default). This is required if the DNS proxy object is used under DeviceVirtual SystemsvsysGeneralDNS Proxy.
   7. Click OK.
   8. Click OK and Commit.
      Optional advanced features such as split DNS can be configured using DNS Proxy Rules. A separate DNS server profile can be used to redirect DNS resolutions matching the Domain Name in a DNS Proxy Rule to another set of DNS servers, if required. Use Case 3 illustrates split DNS.

      If you use two separate DNS server profiles in the same DNS Proxy object, one for the DNS Proxy and one for the DNS proxy rule, the following behaviors occur:

      • If a service route is defined in the DNS server profile used by the DNS Proxy, it takes precedence and is used.
      • If a service route is defined in the DNS server profile used in the DNS proxy rules, it is not used. If the service route differs from the one defined in the DNS server profile used by the DNS Proxy, the following warning message is displayed during the Commit process:

      Warning: The DNS service route defined in the DNS proxy object is different from the DNS proxy rule’s service route. Using the DNS proxy object’s service route.

      • If no service route is defined in any DNS server profile, the global service route is used if needed.