Cisco ASA Redistribution example

Redistribution is a process of sharing routing information between different routing protocols. In Cisco ASA, redistribution enables integration of various routing domains by allowing different protocols to exchange routing information. This improves overall network connectivity and simplifies network management when multiple routing protocols coexist.

The most common routing protocols supported on Cisco ASA include RIP (Routing Information Protocol), OSPF (Open Shortest Path First), and EIGRP (Enhanced Interior Gateway Routing Protocol).

Basic Redistribution Configuration

To configure redistribution on Cisco ASA, use the redistribute command within the routing protocol configuration mode. The basic syntax is:

redistribute [protocol] [process-id] [metric]

OSPF to EIGRP Redistribution Example

router eigrp 100
redistribute ospf 1 metric 1544 2000 255 1 1500

This command redistributes OSPF process 1 routes into EIGRP 100 with specified EIGRP metrics (bandwidth, delay, reliability, load, MTU).

EIGRP to OSPF Redistribution Example

router ospf 1
redistribute eigrp 100 metric-type 1 metric 20

This redistributes EIGRP 100 routes into OSPF process 1 as Type-1 external routes with a metric of 20.

Route Filtering with Route Maps

Route maps provide granular control over which routes are redistributed and how their attributes are modified.

access-list 10 permit 192.168.1.0 0.0.0.255
route-map FILTER-ROUTES permit 10
 match ip address 10
 set metric 50

router ospf 1
redistribute eigrp 100 route-map FILTER-ROUTES

This configuration only redistributes routes matching access-list 10 and sets their metric to 50.

Route Summarization

Summarization reduces routing table size by combining multiple routes into a single summary route.

router ospf 1
summary-address 192.168.0.0 255.255.0.0

This command summarizes all routes within the 192.168.0.0/16 range into a single advertisement.

Comparison of Redistribution Methods

Best Practices

• Use route maps Always implement route maps to control which routes are redistributed and prevent routing loops.

• Set appropriate metrics Configure metrics that reflect the actual path costs to ensure optimal routing decisions.

• Implement summarization Use route summarization in large networks to reduce routing table overhead.

• Monitor routing tables Regularly verify that redistribution is working as expected and not creating suboptimal paths.

Conclusion

Cisco ASA redistribution enables seamless integration between different routing protocols by sharing routing information across protocol boundaries. Proper configuration with route maps and summarization ensures optimal network performance while maintaining control over route propagation.