AOS-W 6.5.3.x | User Guide OSPFv2 | 161
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. Alcatel-Lucent’s implementation of OSPFv2 allows
Alcatel-Lucent switches to deploy effectively in a Layer 3 topology. Alcatel-Lucent switches can act as default
gateway for all clients and forward user packets to the upstream router. An Alcatel-Lucent switch can be used
for Instant AP VPN termination from the branch office, and the OSPF on the switch can be used to redistribute
branch routes into corporate OSPF domain. The information on this chapter is in the following sections:
n Understanding OSPF Deployment Best Practices and Exceptions on page 161
n Understanding OSPFv2 by Example using a WLAN Scenario on page 162
n Understanding OSPFv2 by Example using a Branch Scenario on page 163
n Configuring OSPF on page 165
n Sample Topology and Configuration on page 166
Understanding OSPF Deployment Best Practices and Exceptions
OSPF is a robust routing protocol addressing various link types and deployment scenarios. The Alcatel-Lucent
implementation applies to two main use cases; WLAN Scenarios and Branch Scenario.
n OSPF is disabled by default.
n Alcatel-Lucent switches support only one OSPF instance.
n Convergence takes between 5 and 15 seconds.
n All area types are supported.
n Multiple configured areas are supported.
n An Alcatel-Lucent switch can act as an ABR (Area border router).
n OSPF supports VLAN and GRE tunnel interfaces.
n 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 an Alcatel-Lucent switch is 1100. When running OSPF
over a GRE tunnel between an Alcatel-Lucent switch 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
OAW-4550 8K 8K
OAW-4650 16K 16K
OAW-4750 32K 32K
Table 40: Maximum OSPF Routes
Below are some guidelines regarding deployment and topology for this release of OSPFv2.
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