A virtual router is a function of the firewall that participates in Layer 3 routing. The firewall uses virtual routers to obtain routes to other subnets by you manually defining static routes or through participation in one or more Layer 3 routing protocols (dynamic routes). The routes that the firewall obtains through these methods populate the IP routing information base (RIB) on the firewall. When a packet is destined for a different subnet than the one it arrived on, the virtual router obtains the best route from the RIB, places it in the forwarding information base (FIB), and forwards the packet to the next hop router defined in the FIB. The firewall uses Ethernet switching to reach other devices on the same IP subnet. (An exception to one best route going in the FIB occurs if you are using ECMP, in which case all equal-cost routes go in the FIB.)
The Ethernet, VLAN, and tunnel interfaces defined on the firewall receive and forward Layer 3 packets. The destination zone is derived from the outgoing interface based on the forwarding criteria, and the firewall consults policy rules to identify the security policies that it applies to each packet. In addition to routing to other network devices, virtual routers can route to other virtual routers within the same firewall if a next hop is specified to point to another virtual router.
You can configure Layer 3 interfaces on a virtual router to participate with dynamic routing protocols (BGP, OSPF, OSPFv3, or RIP) as well as add static routes. You can also create multiple virtual routers, each maintaining a separate set of routes that aren’t shared between virtual routers, enabling you to configure different routing behaviors for different interfaces.
Each Layer 3 Ethernet, loopback, VLAN, and tunnel interface defined on the firewall must be associated with a virtual router. While each interface can belong to only one virtual router, you can configure multiple routing protocols and static routes for a virtual router. Regardless of the static routes and dynamic routing protocols you configure for a virtual router, one general configuration is required:
- Gather the required information from your network
- Interfaces on the firewall that you want to perform routing.
- Administrative distances for static, OSPF internal, OSPF external, IBGP, EBGP and RIP.
- Create a virtual router and apply interfaces to it.The firewall comes with a virtual router named default. You can edit the default virtual router or add a new virtual router.
- Select NetworkVirtual Routers.
- Select a virtual router (the one named default or a different virtual router) or Add the Name of a new virtual router.
- Select Router SettingsGeneral.
- Click Add in the Interfaces box
and select an already defined interface from the drop-down.Repeat this step for all interfaces you want to add to the virtual router.
- Click OK.
- Set Administrative Distances for static and dynamic routing.Set Administrative Distances for types of routes as required for your network. When the virtual router has two or more different routes to the same destination, it uses administrative distance to choose the best path from different routing protocols and static routes, by preferring a lower distance.
- Static—Range is 10-240; default is 10.
- OSPF Internal—Range is 10-240; default is 30.
- OSPF External—Range is 10-240; default is 110.
- IBGP—Range is 10-240; default is 200.
- EBGP—Range is 10-240; default is 20.
- RIP—Range is 10-240; default is 120.
- Commit virtual router general settings.Click OK and Commit.
- Configure Ethernet, VLAN, loopback, and tunnel interfaces as needed.
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