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.
Configure a DNS Proxy for a Virtual System
For each virtual system, specify the DNS Proxy to use. Select Device > Virtual Systems and click Add. Enter the ID of the virtual system (range is 1-255), and an optional Name, in this example, Corp1 Corporation. On the General tab, choose a DNS Proxy or create a new one. For Interfaces, click Add. In this example, Ethernet1/20 is dedicated to this tenant. For Virtual Routers, click Add. A virtual router is assigned to the virtual system in order to separate routing functions. Click OK to save the configuration.
Configure a DNS Proxy and a server profile to support DNS resolution for a virtual system. Select Network > DNS Proxy and click Add. Click Enable and enter a Name for the DNS Proxy. For Location, select the virtual system of the tenant. (You could choose the Shared DNS Proxy resource instead.) 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. 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. Click OK to save the DNS Server Profile. Click OK and Commit to save the DNS Proxy.
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.

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