OSPF Multi-Area & Route Redistribution

VCF 9.0Intermediatevcap-advanced⏱ 150 min

Objectives

Configure OSPF Area 0 backbone, Area 1 (Site-A), Area 2 (Site-B); redistribute static routes; verify end-to-end path.

Prerequisites

VCF lab environment deployed and operational

Lab Environment

Standard VCF lab environment for Advanced VCF 9.0 Networking (NSX & Advanced Routing)

Tasks

Task 1 OSPF Multi-Area & Route Redistribution

Configure OSPF Area 0 backbone, Area 1 (Site-A), Area 2 (Site-B); redistribute static routes; verify end-to-end path.

Step 1

Deploy 3 Tier-0 routers: backbone-router, site-a-router, site-b-router.

Step 2

Configure OSPF backbone (Area 0): backbone-router connected to site-a-router and site-b-router.

Step 3

Configure Area 1: site-a-router advertises site-a pod network (10.100.0.0/16) as OSPF intra-area route.

Step 4

Configure Area 2: site-b-router advertises site-b pod network (10.200.0.0/16).

Step 5

Verify LSA flooding: show ospf database (all routers see Type 1/2/3 LSAs).

Step 6

Configure static default route on site-a-router: 0.0.0.0/0 → 10.0.0.1 (ISP).

Step 7

Redistribute static route into OSPF Area 1 as external route (Type 5 LSA).

Step 8

On site-b-router, verify default route learned via OSPF: show ip route | grep 0.0.0.0

Step 9

Test end-to-end: From site-b, reach ISP via site-a (asymmetric path acceptable).

Step 10

Modify OSPF costs on site-a-router to increase Area 1 exit cost; verify site-b prefers direct path if available.

Validation Gate

Check: Verify lab completion

Expected: Lab exercise completed successfully

Common Errors

OSPF area type mismatch between NSX and physical routers

Fix: If physical router has area 1 as NSSA but NSX configures it as stub, adjacency forms but routes don't propagate correctly. Verify area types match on both sides: 'get ospf neighbor' on NSX Edge, 'show ospf neighbor' on physical router.

Route redistribution loop between OSPF and BGP

Fix: Redistributing OSPF→BGP and BGP→OSPF without route tags creates a loop: routes learned via BGP are redistributed into OSPF, then back to BGP. Use route tags to prevent re-redistribution: tag routes at redistribution point, filter tagged routes at the other redistribution point.

OSPF hello/dead timer mismatch causing flapping adjacencies

Fix: OSPF adjacency requires matching hello and dead intervals. NSX default: hello 10s, dead 40s. If the physical router uses different timers, adjacency flaps. Match timers on both sides or use BFD for fast failure detection alongside OSPF.

Final Validation

Lab completed successfully

✓ All steps completed → No errors observed

Cleanup / Restore

• Revert to snapshot if needed

Design Reflection (VCDX)

OSPF multi-area design shows enterprise networking depth. VCDX panelists test route redistribution, loop prevention, and area design rationale.

⚠ Known Pitfalls (from Community KB)

Redistributing between OSPF and BGP without route tags — creates routing loops.

Mismatching OSPF timers between NSX and physical routers — causes adjacency flapping.

Mark complete