🔄 OSPF-EIGRP Route Redistribution Lab

Mastering Selective Route Redistribution and Filtering

🚀 Welcome to Route Redistribution Mastery

💡 Lab Focus

This lab demonstrates controlled route redistribution between OSPF and EIGRP, focusing on selective route sharing using access lists and route maps.

🎯 What You'll Learn

  • Configure mutual redistribution between OSPF and EIGRP
  • Implement selective route filtering using access lists
  • Apply route maps for granular redistribution control
  • Set appropriate metrics for redistributed routes
  • Prevent routing loops with administrative distance manipulation
  • Verify redistribution effectiveness and troubleshoot issues
  • Understand the impact of route summarization on redistribution

🏛️ Lab Environment

This lab uses a multi-router topology with separate OSPF and EIGRP domains connected through redistribution routers. You'll configure selective redistribution to control which EIGRP routes are shared into the OSPF domain.

Ready to Begin! Navigate through the tabs above to complete this comprehensive route redistribution lab. Start with the Topology tab to understand the network layout.

🏗️ Network Topology

OSPF Area 0 EIGRP AS 100 [R1] ---- [R2] ---- [R3] ---- [R4] ---- [R5] | | | | | 10.1.1.0/24 | 10.3.3.0/24 | 10.5.5.0/24 10.2.2.0/24 10.4.4.0/24 OSPF Domain Redistribution EIGRP Domain Area 0 Router (R3) AS 100 Additional Networks: - R1 Loopback: 192.168.1.1/32 (OSPF) - R2 Loopback: 192.168.2.1/32 (OSPF) - R4 Loopback: 172.16.4.1/32 (EIGRP) - R5 Loopback: 172.16.5.1/32 (EIGRP) R3 Configuration: - Interface to R2: OSPF Area 0 - Interface to R4: EIGRP AS 100 - Redistribution Point Between Domains

🔌 Interface Assignments

Router Interface IP Address Connected To Protocol
R1 GigabitEthernet0/0 10.1.2.1/24 R2 OSPF Area 0
R2 GigabitEthernet0/0 10.1.2.2/24 R1 OSPF Area 0
R2 GigabitEthernet0/1 10.2.3.2/24 R3 OSPF Area 0
R3 GigabitEthernet0/0 10.2.3.3/24 R2 OSPF Area 0
R3 GigabitEthernet0/1 10.3.4.3/24 R4 EIGRP AS 100
R4 GigabitEthernet0/0 10.3.4.4/24 R3 EIGRP AS 100
R4 GigabitEthernet0/1 10.4.5.4/24 R5 EIGRP AS 100
R5 GigabitEthernet0/0 10.4.5.5/24 R4 EIGRP AS 100

💡 Topology Key Points

R3 serves as the redistribution point between OSPF Area 0 and EIGRP AS 100. Only specific EIGRP routes (172.16.5.0/24) will be redistributed into OSPF, while all OSPF routes will be shared into EIGRP.

📋 Prerequisites and Planning

🔧 Required Knowledge

  • Understanding of OSPF and EIGRP routing protocols
  • Familiarity with routing tables and administrative distances
  • Experience with access control lists (ACLs)
  • Knowledge of route maps and policy routing
  • Basic understanding of redistribution concepts

🛠️ Equipment Requirements

Hardware/Software Needed

  • 5 Cisco routers (physical or virtual)
  • IOS version supporting OSPF and EIGRP
  • Console access for configuration
  • Network monitoring tools (optional)

📝 Pre-Lab Preparation

1

Base IP Configuration

Ensure all interfaces are configured with correct IP addresses as shown in the topology.

2

Routing Protocol Setup

Configure OSPF on R1, R2, and R3 (left side). Configure EIGRP on R3, R4, and R5 (right side).

3

Loopback Interfaces

Create loopback interfaces on each router for testing redistribution.

⚠️ Important Considerations

Routing Loop Prevention: When implementing mutual redistribution, always use route tagging or administrative distance manipulation to prevent routing loops.
Metric Compatibility: OSPF uses cost while EIGRP uses composite metric. Set appropriate seed metrics during redistribution.
Common Pitfall: Without proper filtering, all routes from both domains will be redistributed, potentially causing suboptimal routing and loops.

⚙️ Step-by-Step Configuration

1

Configure Base OSPF (R1, R2, R3)

# Router R1 Configuration router ospf 1 router-id 1.1.1.1 network 10.1.2.0 0.0.0.255 area 0 network 192.168.1.0 0.0.0.255 area 0 interface loopback 0 ip address 192.168.1.1 255.255.255.255 # Router R2 Configuration router ospf 1 router-id 2.2.2.2 network 10.1.2.0 0.0.0.255 area 0 network 10.2.3.0 0.0.0.255 area 0 network 192.168.2.0 0.0.0.255 area 0 interface loopback 0 ip address 192.168.2.1 255.255.255.255
2

Configure Base EIGRP (R3, R4, R5)

# Router R4 Configuration router eigrp 100 network 10.3.4.0 0.0.0.255 network 10.4.5.0 0.0.0.255 network 172.16.4.0 0.0.0.255 no auto-summary interface loopback 0 ip address 172.16.4.1 255.255.255.255 # Router R5 Configuration router eigrp 100 network 10.4.5.0 0.0.0.255 network 172.16.5.0 0.0.0.255 no auto-summary interface loopback 0 ip address 172.16.5.1 255.255.255.255
3

Configure R3 with Both Protocols

# Router R3 - OSPF Configuration router ospf 1 router-id 3.3.3.3 network 10.2.3.0 0.0.0.255 area 0 # Router R3 - EIGRP Configuration router eigrp 100 network 10.3.4.0 0.0.0.255 no auto-summary

💡 Verification Checkpoint

Before proceeding with redistribution, verify that OSPF is working between R1-R2-R3 and EIGRP is working between R3-R4-R5. Use "show ip route" to confirm routing tables.

4

Create Access List for Selective Redistribution

# Router R3 - Create ACL to permit only R5's loopback access-list 1 permit 172.16.5.0 0.0.0.255 # Alternative: Use prefix-list for more granular control ip prefix-list EIGRP-TO-OSPF seq 10 permit 172.16.5.0/24

This access list allows only the 172.16.5.0/24 network (R5's loopback) to be redistributed from EIGRP into OSPF.

5

Configure Route Map for Advanced Control

# Router R3 - Route map for EIGRP to OSPF redistribution route-map EIGRP-TO-OSPF permit 10 match ip address 1 set metric 100 set tag 100 # Deny all other routes (implicit deny) route-map EIGRP-TO-OSPF deny 20 # Route map for OSPF to EIGRP redistribution route-map OSPF-TO-EIGRP permit 10 set metric 100000 100 255 1 1500 set tag 200
6

Implement Redistribution on R3

# Router R3 - Redistribute EIGRP into OSPF (selective) router ospf 1 redistribute eigrp 100 route-map EIGRP-TO-OSPF subnets # Router R3 - Redistribute OSPF into EIGRP (all routes) router eigrp 100 redistribute ospf 1 route-map OSPF-TO-EIGRP
Critical Note: The "subnets" keyword is essential in OSPF redistribution to include subnet information. Without it, only classful networks are redistributed.
7

Configure Administrative Distance to Prevent Loops

# Router R3 - Adjust AD for redistributed routes router ospf 1 distance 115 0.0.0.0 255.255.255.255 2 router eigrp 100 distance 115 0.0.0.0 255.255.255.255 3 # Create ACL for redistributed routes identification access-list 2 permit any access-list 3 permit any
8

Configure Route Tagging for Loop Prevention

# Router R3 - Enhanced route maps with tagging route-map EIGRP-TO-OSPF permit 10 match ip address 1 match tag 0 set metric 100 set tag 100 route-map OSPF-TO-EIGRP permit 10 match tag 0 set metric 100000 100 255 1 1500 set tag 200 # Deny routes with redistribution tags route-map EIGRP-TO-OSPF deny 5 match tag 200 route-map OSPF-TO-EIGRP deny 5 match tag 100
Configuration Complete! Your selective redistribution is now configured. Only R5's loopback (172.16.5.0/24) should appear in OSPF routing tables, while all OSPF routes should be visible in EIGRP domain.

🔧 Troubleshooting Guide

1

Routes Not Being Redistributed

Problem: EIGRP routes are not appearing in OSPF routing table.
Solution:
  • Verify access list is permitting the correct networks
  • Check route map configuration and sequence numbers
  • Ensure "subnets" keyword is used in OSPF redistribution
  • Confirm the route exists in the source routing protocol
# Debug commands for troubleshooting debug ip routing debug ip ospf database-timer debug eigrp packets # Verification commands show ip route eigrp show ip route ospf show ip protocols
2

Wrong Routes Being Redistributed

Problem: More routes than expected are being redistributed.
Solution:
  • Review access list entries for accuracy
  • Check route map match conditions
  • Verify implicit deny is working correctly
  • Use more specific prefix lists instead of access lists
# Test access list matching show access-lists show route-map EIGRP-TO-OSPF show ip prefix-list detail # Clear routing processes to refresh clear ip route * clear ip ospf process clear ip eigrp neighbors
3

Routing Loops Detected

Problem: Routing loops causing network instability.
Solution:
  • Implement route tagging to prevent loops
  • Adjust administrative distances
  • Use split-horizon where applicable
  • Consider using distribute lists
# Check for routing loops traceroute 172.16.5.1 show ip route 172.16.5.0 ping 172.16.5.1 source loopback0 # Monitor routing updates debug ip rip debug ip ospf adj debug eigrp packets hello
4

Incorrect Metrics After Redistribution

Problem: Redistributed routes have suboptimal metrics.
Solution:
  • Set appropriate seed metrics in redistribution commands
  • Use route maps to set specific metrics
  • Consider default metrics for each protocol
  • Test path selection after metric changes
# Check current metrics show ip route detail show ip ospf database external show ip eigrp topology # Set appropriate metrics router ospf 1 default-metric 100 router eigrp 100 default-metric 100000 100 255 1 1500
5

Redistribution Not Working After Reboot

Problem: Configuration doesn't survive router reboot.
Solution:
  • Verify configuration is saved to startup-config
  • Check for any missing dependencies
  • Ensure proper configuration sequence
  • Validate all referenced ACLs and route maps exist
# Save and verify configuration copy running-config startup-config show startup-config | include redistrib show startup-config | include access-list show startup-config | include route-map # Verify after reboot show version show ip protocols show running-config | section router

💡 Pro Troubleshooting Tips

Always use systematic approach: verify routing protocol operation first, then check redistribution configuration, test connectivity, and finally optimize performance. Document changes and maintain configuration backups.

✅ Verification Procedures

1

Verify Routing Protocol Operation

# Check OSPF neighbors and database show ip ospf neighbor show ip ospf database show ip ospf interface brief # Check EIGRP neighbors and topology show ip eigrp neighbors show ip eigrp topology show ip eigrp interfaces

Expected Results:

  • OSPF neighbors in FULL state between R1-R2-R3
  • EIGRP neighbors established between R3-R4-R5
  • All interfaces participating in respective protocols
2

Verify Route Redistribution

# Check redistributed routes in OSPF show ip route ospf show ip ospf database external # Check redistributed routes in EIGRP show ip route eigrp show ip eigrp topology | include Extern # Verify specific redistributed route show ip route 172.16.5.0 show ip route 192.168.1.0

Expected Results:

  • 172.16.5.0/24 appears as OSPF External (O E2) in R1 and R2
  • OSPF routes appear as EIGRP External (D EX) in R4 and R5
  • 172.16.4.0/24 should NOT appear in OSPF domain
3

Test End-to-End Connectivity

# Test connectivity from OSPF domain to allowed EIGRP route ping 172.16.5.1 source 192.168.1.1 # Test connectivity from EIGRP domain to OSPF routes ping 192.168.1.1 source 172.16.5.1 ping 192.168.2.1 source 172.16.4.1 # Verify routing path traceroute 172.16.5.1 source 192.168.1.1 traceroute 192.168.1.1 source 172.16.5.1
Success Criteria: All pings should succeed, demonstrating bidirectional connectivity through the redistribution point.
4

Verify Filtering Effectiveness

# From R1, verify you cannot reach R4's loopback directly ping 172.16.4.1 source 192.168.1.1 # Check routing table to confirm 172.16.4.0 is not present show ip route | include 172.16.4 # Verify access list hit counts show access-lists 1 show route-map EIGRP-TO-OSPF

Expected Results:

  • Ping to 172.16.4.1 should fail (no route)
  • 172.16.4.0/24 should not appear in OSPF routing tables
  • Access list should show hit counts for permitted routes
5

Analyze Route Metrics and Path Selection

# Check OSPF metric for redistributed route show ip route 172.16.5.0 detail show ip ospf database external 172.16.5.0 # Check EIGRP metric for redistributed routes show ip route 192.168.1.0 detail show ip eigrp topology 192.168.1.0 # Compare administrative distances show ip protocols show ip route summary

Metric Analysis:

  • OSPF external routes should have metric 100 (from route map)
  • EIGRP external routes should show composite metric from seed values
  • Administrative distances should prevent routing loops
6

Final Validation Checklist

✅ Complete Verification Checklist:

  • ☐ OSPF neighbors established and stable
  • ☐ EIGRP neighbors established and stable
  • ☐ Only 172.16.5.0/24 redistributed into OSPF
  • ☐ All OSPF routes redistributed into EIGRP
  • ☐ End-to-end connectivity working
  • ☐ Filtering preventing unwanted route redistribution
  • ☐ No routing loops detected
  • ☐ Appropriate metrics assigned

🧠 Knowledge Assessment

1. What is the primary purpose of using route maps in redistribution?
2. Why is the "subnets" keyword important in OSPF redistribution?
3. What mechanism helps prevent routing loops in mutual redistribution?
4. In EIGRP redistribution, what does the metric "100000 100 255 1 1500" represent?
5. What happens if you forget to configure "no auto-summary" in EIGRP?
6. Which command would you use to view redistributed external routes in OSPF?
7. In this lab, why was only 172.16.5.0/24 redistributed into OSPF?