User's Manual

Dell Networking W-Series ArubaOS 6.4.x| User Guide OSPFv2 | 205
Chapter 7
OSPFv2
OSPFv2 (Open Shortest Path First) is a dynamic Interior Gateway routing Protocol (IGP) based on IETF RFC
2328. The OSPF uses the shortest or fastest routing path. Dell’s implementation of OSPFv2 allows Dell
controllers to deploy effectively in a Layer 3 topology. Dell controllers can act as default gateway for all clients
and forward user packets to the upstream router. An Dell controller can be used for Instant AP VPN
termination from the branch office, and the OSPF on the controller can be used to redistribute branch routes
into corporate OSPF domain. The information on this chapter is in the following sections:
l Understanding OSPF Deployment Best Practices and Exceptions on page 205
l Understanding OSPFv2 by Example using a WLAN Scenario on page 206
l Understanding OSPFv2 by Example using a Branch Office Scenario on page 207
l Configuring OSPF on page 208
l Sample Topology and Configuration on page 210
Understanding OSPF Deployment Best Practices and Exceptions
OSPF is a robust routing protocol addressing various link types and deployment scenarios. The Dell
implementation applies to two main use cases; WLAN Scenarios and Branch Office Scenario.
l OSPF is disabled by default.
l Dell controllers support only one OSPF instance.
l Convergence takes between 5 and 15 seconds.
l All area types are supported.
l Multiple configured areas are supported.
l A Dell controller can act as an ABR (Area border router).
l OSPF supports VLAN and GRE tunnel interfaces.
l To run OSPF over IPSec tunnels, a Layer 3 GRE tunnel is configured between two routers with GRE
destination addresses as the inner address of the IPsec tunnel. OSPF is enabled on the Layer 3 GRE tunnel
interface, and all of the OSPF control packets undergo GRE encapsulation before entering the IPsec tunnels.
The default MTU value for a Layer 3 GRE tunnel in a Dell controller is 1100. When running OSPF over a GRE
tunnel between a Dell controller and another vendor’s router, the MTU values must be the same on both
sides of the GRE tunnel.
The following table provides information on the maximum OSPF routes supported for various platforms:
Platform Branches Routes
W-3600 8K 8K
W-6000M3 8K 8K
W-7210 8K 8K
Table 35: Maximum OSPF Routes