IP Routing Features
Contents
Designated Routers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-49
OSPF Area Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-51
Backbone Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-52
Normal Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-52
Not-So-Stubby-Area (NSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-53
Stub Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-54
OSPF RFC Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-54
Reducing AS External LSAs and Type-3 Summary LSAs . . . . . . . . . . 5-54
Algorithm for AS External LSA Reduction . . . . . . . . . . . . . . . . . . 5-55
Replacing Type-3 Summary LSAs and Type-7 Default External
LSAs with a Type-3 Default Route LSA . . . . . . . . . . . . . . . . . . . . . 5-56
Equal Cost Multi-Path Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-57
Dynamic OSPF Activation and Configuration . . . . . . . . . . . . . . . . . . . 5-59
General Configuration Steps for OSPF . . . . . . . . . . . . . . . . . . . . . . . . . 5-60
Configuration Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-61
OSPF Global and Interface Settings . . . . . . . . . . . . . . . . . . . . . . . 5-61
Configuring OSPF on the Routing Switch . . . . . . . . . . . . . . . . . . . . . . 5-63
1. Enable IP Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-63
2. Enable Global OSPF Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-63
3. Changing the RFC 1583 OSPF Compliance Setting . . . . . . . . . 5-64
4. Assign the Routing Switch to OSPF Areas . . . . . . . . . . . . . . . . 5-66
5. Assign VLANs and/or Subnets to Each Area . . . . . . . . . . . . . . 5-70
6. Optional: Assigning Loopback Addresses to an Area . . . . . . . 5-72
7. Optional: Configure for External Route Redistribution in
an OSPF Domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-74
8. Optional: Configure Ranges on an ABR To Reduce
Advertising to the Backbone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-77
9. Optional: Influence Route Choices by Changing the
Administrative Distance Default . . . . . . . . . . . . . . . . . . . . . . . . . . 5-80
10: Optional: Change OSPF Trap Generation Choices . . . . . . . . 5-81
11. Optional: Adjust Performance by Changing the VLAN
or Subnet Interface Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-82
12. Optional: Configuring OSPF Interface Authentication . . . . . . . . . 5-87
13. Configuring an ABR To Use a Virtual Link to the Backbone . . . . 5-89
Configuring a Virtual Link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-90
Optional: Adjust Virtual Link Performance by Changing
the Interface Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-91
5-3
