Basic Redistribution
Redistribute Static Routes
router ospf 1
redistribute static subnets
Without subnets: Only classful networks redistributed
Redistribute Connected Interfaces
router ospf 1
redistribute connected subnets
Redistribute from Another Protocol (EIGRP)
router ospf 1
redistribute eigrp 1 subnets
E1 vs E2 External Routes
| Type | Metric Calculation | Use When |
|---|---|---|
| E2 (default) | Fixed external cost | Single exit point |
| E1 | External + internal cost | Multiple exit points |
Set metric type:
router ospf 1
redistribute static subnets metric-type 1
Setting the Metric
Default metric: 20 (except BGP = 1)
Set custom metric:
router ospf 1
redistribute static subnets metric 50
Route Tagging (Loop Prevention)
Tag routes during redistribution:
router ospf 1
redistribute eigrp 1 subnets tag 100
Filter tagged routes:
route-map FILTER deny 10
match tag 100
route-map FILTER permit 20
router ospf 1
distribute-list route-map FILTER in
Complete Example
R1 (ASBR redistributing static)
ip route 172.16.50.0 255.255.255.0 Null0
ip route 172.16.51.0 255.255.255.0 Null0
router ospf 1
router-id 1.1.1.1
network 10.0.0.0 0.0.255.255 area 0
redistribute static subnets metric 50 metric-type 1
Verification (Other Routers)
R2# show ip route ospf
O E1 172.16.50.0/24 [110/51] via 10.1.1.1
O E1 172.16.51.0/24 [110/51] via 10.1.1.1
O E1 = External Type 1
Metric 51 = 50 (external) + 1 (internal cost)
Best Practices
1. Always Use subnets Keyword
redistribute static subnets ← Include this
2. Set Explicit Metrics
redistribute eigrp 1 subnets metric 100
3. Use Route Maps for Control
route-map REDIS permit 10
match ip address prefix-list ALLOWED
router ospf 1
redistribute static route-map REDIS subnets
4. Tag Redistributed Routes
Prevents routing loops in mutual redistribution scenarios
Summary
✅ Redistribute command — Inject routes from other sources
✅ subnets keyword — Always include for subnet routes
✅ E1 vs E2 — Choose based on exit point count
✅ Metric — Set explicitly for control
✅ Route tagging — Prevent loops
Series Complete! Review Design Best Practices (Article 30)
Internal Links:
- ← Route Summarization (Article 28)
- ← Advertise Default Route (Article 11)
- ← OSPF Stub Areas (Article 14)
- → Design Best Practices (Article 30)
