June 2013 | Reading time: 7 min
As enterprise networks scale and diversify, routing protocols must be tuned to accommodate both efficiency and reliability. Enhanced Interior Gateway Routing Protocol (EIGRP), Cisco’s proprietary hybrid routing protocol, has long been a cornerstone in many enterprise infrastructures. One of its lesser-known but powerful features is the concept of a stub router. Introduced to improve control over routing updates and minimize unnecessary overhead, EIGRP stub routers are essential in large-scale, spoke-based topologies.
What Is an EIGRP Stub Router?
An EIGRP stub router is a device configured to limit the type of routing information it advertises to its EIGRP neighbors. The primary goal is to reduce the size of EIGRP updates sent across the network and to prevent certain routes from being used in transit, which can avoid suboptimal routing and improve overall convergence times.
This is particularly useful in hub-and-spoke topologies where remote sites (spokes) should not become transit paths for traffic between other sites. When a router is designated as a stub, it tells its upstream peers (usually the hub routers) not to use it as a transit route for anything beyond its directly connected networks.
Why Use Stub Routers?
There are multiple enterprise-grade reasons for using EIGRP stub routers:
- Reduced Routing Overhead: Spoke routers don’t need full topology information, just enough to reach the hub.
- Faster Convergence: Since fewer paths need recalculating, failovers and changes converge faster.
- Improved Stability: Prevents routing loops and minimizes churn from remote sites.
- Security: Keeps routing control centralized, reducing exposure to misconfigured or rogue spokes.
How to Configure EIGRP Stub Routers
Configuring a router as a stub is straightforward. Below is an example of a basic configuration:
router eigrp 100
eigrp stub connected static
In this configuration:
connected- Advertises connected routes only.static- Includes static routes if defined.
Other stub options include summary, redistributed, and receive-only, allowing fine-tuning based on routing policy.
Use Case: Branch Office Design
Consider a scenario where a large enterprise has 100 branch offices connected to two central data centers via MPLS. Each branch has a single WAN router participating in EIGRP with the hubs. These branch routers should never route traffic between branches; all inter-site communication must traverse the data centers.
By configuring each branch router as an EIGRP stub, you ensure they only advertise their local networks and do not participate in forwarding traffic for other sites. This improves route summarization and scalability.
Limitations and Considerations
- EIGRP stub routers only work effectively if all neighbors support the feature. Devices must be Cisco and compatible with EIGRP stub.
- If a stub router is the only available route, it may still be used depending on fallback logic.
- Care must be taken when integrating with redistribution—especially if EIGRP routes are being injected from OSPF or static.
Monitoring and Troubleshooting
You can verify the stub status with the following command:
show ip eigrp neighbors detail
Or use:
show ip protocols
These outputs confirm the router’s stub status and the route types it advertises.
Conclusion
Stub routing within EIGRP is a powerful design tool for optimizing route propagation and stability in enterprise networks. When combined with other EIGRP capabilities like route summarization, filtering, and authentication, stub routers contribute to highly scalable and resilient topologies. For enterprises running EIGRP today, especially those with numerous branches or remote offices, implementing stub routers is a best practice that pays dividends in network health and simplicity.