Dell 6.2 Chapte r 10

DellPowerConnect W- Series ArubaOS 6.2 | User Guide OSPFv2 | 152
Chapte r 10
OSPFv2
OSPFv2 (OpenShortest P ath First) is a dynamic Interior Gateway routing Protocol (IGP) based on I ETF RFC
2328. The premise of OSPF is that the shortest or fastest routing path is used. Dell’s implementation of OSPFv2
allows Dell controllersto deploy effectively in a Layer 3 topology. Dell controllers can act as default gateway for all
clients and forwarduser packets to the upstream router.The i nformationi n this chapter is in the following sections:
l"UnderstandingOSPF Deployment Best Practi ces and Exceptions" on page 152
l"UnderstandingOSPFv2 by Example using a WLAN Scenario" on page 153
l"UnderstandingOSPFv2 by Example using a Branch Office Scenario" on page 154
l"ConfiguringOSPF " on page 155
l"SampleTopology and Configuration" on page 157
Understanding OSP F Deployment Best Practices an d Exceptions
OSPF is a robust routing protocol addressing various link types and deployment scenarios, the Dell implementation
applies to two main use cases; WLAN Scenario and Branch Office Scenario.
lOSPF is disabled by default.
lDell controllerssupport only one OSPF instance.
lMaximumOSPF routes is 1 K.
lConvergencetakes between 5 and 15 seconds.
lAll areat ypes are supported.
lMultipleconfigured areas are supported.
lA Dell controller can act as ABR (Area border router).
lOSPF supports VLAN and GRE tunnel interfaces.
lTo runOSPF over IPSec tunnels,a Layer 3 GRE tunnel is configuredbetween two routers with GRE destination
addressesas t hei nneraddress of the IPsec tunnel. OSPF is enabled on the Layer3 GRE tunnel interface andall
of the OSPF controlpackets undergo GRE encapsulation before entering the IPsec tunnels.
The defaultMTU value for a Layer 3 GRE tunnel in a Dell controller is 1100. When runningOSPF over a GRE
tunnelbetween a Dell controllerand another vendor’s router, the MTU valuesmust be the same on both sides
of the GRE tunnel.
Below are some guidelines regardingdeployment and topology for this release of OSPFv2.
lIn WLAN scenario, configure the Dell controllerand all upstream routers in totally stub area; in Branch Office
scenario, configureas s tub area so that the Branch Office controllercan receive corporate subnets.
lIn the WLAN scenario upstreamrouter, only configure the interface connected to the controlleri nt hesame area
as the controller.This will minimize the number of local subnet addressesadvertised by the upstream router to
the controller.
lUse the upstreamrouter as the designated router (DR) for the link/interface between the controllerand the
upstreamrouter.