Route redistribution shares routes between different routing protocols – but introduces complexity and potential routing loops. It happens on a router running multiple protocols, which acts as the redistribution point, translating routes from one protocol’s metric to another’s.

When is it used?

• Networks with multiple routing protocols
• Migration between protocols
• Joining administrative domains

Facts (CCNA)

Point	Fact
Where	Router running multiple protocols
Direction	One- or two-way
Metric	Often must be set manually
AD	The receiving protocol’s AD
Risk	Routing loops
Scope	IGP ↔ IGP, static ↔ IGP

Metric & translation (important)

• Protocols use different metrics: OSPF needs cost, EIGRP needs a composite metric
• Without a correct metric the route becomes unusable
• Redistributed routes get the AD of the receiving protocol

Risks / pitfalls (exam)

• Routing loops, route feedback, suboptimal routing, missing/wrong metric
• Avoid with: route-maps, filtering, route tags

CLI

! Static → OSPF   (`subnets` is critical – without it only classful routes)
router ospf 1
 redistribute static subnets
!
! Connected → OSPF
router ospf 1
 redistribute connected subnets
!
! Static/Connected → EIGRP (EIGRP REQUIRES a metric: bandwidth delay reliability load mtu)
router eigrp 100
 redistribute static metric 10000 100 255 1 1500
 redistribute connected metric 10000 100 255 1 1500
!
! OSPF ↔ EIGRP two-way – TRAP: two-way redistribution = loop risk
router ospf 1
 redistribute eigrp 100 subnets
router eigrp 100
 redistribute ospf 1 metric 10000 100 255 1 1500

Verification (must-know)

show ip route
show ip route ospf
show ip route eigrp