Routing Concepts and Troubleshooting Quiz

RPF Check

• The default mode for RPF check is feasible path mode.

Feasible Path Mode

• In feasible path mode, a packet is accepted as long as there is one active route to the source IP through the incoming interface.
• Feasible path mode was formerly known as "asymmetric routing".
• The packet does not need to take the best route in feasible path mode.

Packet Acceptance

• The packet from 10.4.0.1 to 10.1.0.1 gets accepted.
• The packet from 172.16.1.1 to 10.1.0.1 gets accepted.

Route Information

• There is no active route to the IP address 172.16.1.1 through port3.
• The destination IP of the packet that is accepted is 10.1.0.1.
• The destination IP of the packet that is not accepted is not specified.

Routing

• The default route is used for routing packets when there is no specific route.
• When the action in a policy route is Stop Policy Routing, FortiGate goes to the Kernel routing table.
• The purpose of the Forwarding Information Base (FIB) is to facilitate routing decisions.
• In a FortiGate high availability (H-A) cluster, the secondary FortiGate has a dedicated routing table.
• If there is no match in any of the routing tables, FortiGate uses the default route.
• The first criteria used by FortiGate to select a route when there are multiple routes to a destination is the longest prefix match.
• FortiGate uses the lowest metric as the tiebreaker for dynamic routes when there are multiple routes with the same prefix length.
• FortiGate uses the lowest priority as the tiebreaker for static routes.
• Equal cost multipath (ECMP) is used for load balancing and redundancy.

Route Addition

• FortiGate adds a static route to the routing table when the route is configured manually.

RPF Protection

• The reverse path forwarding (RPF) check protects against spoofing attacks.

Routing Table Lookup

• FortiGate performs routing table lookup only once for any session.
• The route information in the session table is updated after a routing change.
• FortiGate usually performs one routing lookup for a traffic session.
• FortiGate performs additional routing table lookups when the routing table changes or the session is re-established.

Route Decision

• FortiGate decides routes based on the routing table and policy routes.

Policy Routes

• The command to view FortiGate's policy routes is "diag debug appl cs-route".

Routing Modules

• FortiGate has two routing modules: the kernel routing table and the FIB.

Routing Information

• After performing routing lookups for a session, FortiGate stores the routing information in the session table.
• The route information in the session table is updated after a routing change.
• FortiGate is a stateful device.

Test your knowledge on routing concepts and troubleshooting with this quiz. Learn about route lookup in FortiGate and how routing information is stored in session tables and route cache. Find out what happens to route information after a routing change.