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Copyright © 1997 Cisco Systems, Inc.
6-39CSE: Networking Fundamentals — WAN Basics
© 1999, Cisco Systems, Inc.
www.cisco.com
EIGRP Convergence
EIGRP Convergence
Steps of convergence:
1. C detects link failure; has no FS, goes into active convergence
- No successor candidates present in topology database
2. C sends query to B and D to get logical successor
- Because no route with a lower feasible distance available
3. D’s response indicates no logical successor
4. B’s response indicates FS with higher feasible distance
5. C accepts new path and distance, adds route via B to table
6. Sends Flash update about higher metric, goes to D and B
- Only higher metric propagated in triggered update
Convergence time to F: approximately 2 seconds
S1
S0
E1
E0
S0
S0
E0
F
F
E
E
B
B
A
A
C
C
D
D
6-40CSE: Networking Fundamentals — WAN Basics
© 1999, Cisco Systems, Inc.
www.cisco.com
OSPF Convergence
OSPF Convergence
S1
S0
E1
E0
S0
S0
E0
Steps of convergence:
1. C detects link failure; sends link -state advertisement, goes to D and B
- Topology change is detected, traffic forwarding suspended
2. All routers update topology database; copy LSA and flood to neighbors
- All devices have topological awareness
3. All routers run Dijkstra algorithm, generate new routing table
- Route via B in routing tables, traffic forwarding resumed
Convergence time to F: approximately 6 seconds
F
F
E
E
B
B
A
A
C
C
D
D
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