When a firewall is enabled for multiple virtual systems,
the virtual systems inherit the global service and service route settings.
For example, the firewall can use a shared email server to originate
email alerts to all virtual systems. In some scenarios, you’d want
to create different service routes for each virtual system.
One use case for configuring service routes at the virtual system
level is if you are an ISP who needs to support multiple individual
tenants on a single Palo Alto Networks firewall. Each tenant requires
custom service routes to access service such as DNS, Kerberos, LDAP,
NetFlow, RADIUS, TACACS+, Multi-Factor Authentication, email, SNMP
trap, syslog, HTTP, User-ID Agent, VM Monitor, and Panorama (deployment
of content and software updates). Another use case is an IT organization
that wants to provide full autonomy to groups that set servers for
services. Each group can have a virtual system and define its own
You can select a virtual router for a service route in
a virtual system; you cannot select the egress interface. After
you select the virtual router and the firewall sends the packet
from the virtual router, the firewall selects the egress interface
based on the destination IP address. Therefore, if a virtual system
has multiple virtual routers, packets to all of the servers for
a service must egress out of only one virtual router. A packet with
an interface source address may egress a different interface, but
the return traffic would be on the interface that has the source
IP address, creating asymmetric traffic.