Back to EIGRP GuideENARSI convergence design

EIGRP Stub Routing: Control Queries at the Branch

Use EIGRP stub routing to tell upstream routers that a branch is not a transit path, reduce query scope, and advertise only the route types the design needs.

Query ScopeConnectedSummaryLeak MapNamed Mode

Stub Routing at a Glance

A stub router can still learn routes and send selected local routes. Its neighbors avoid sending it Queries for destinations that the stub cannot reach as a transit router.

Primary purposeContain Queries

Typical locationBranch edge

Classic default optionsConnected + summary

Neighbor learns statusStub TLV

Simple meaning: “Send traffic to me for my advertised networks, but do not ask me to find another path through the network.”

1. Recognize a Good Stub Design

CoreTransit capableHas several alternate paths

WANEIGRP AS 100Queries stop at branch

Branch R3EIGRP stubOne useful path toward core

LANPassive10.30.0.0/16

UsersBranch prefixesAdvertised toward core

A single-exit or limited-transit branch is the common stub use case.

Do not apply blindly: A router that must carry traffic between upstream neighbors is not a simple stub.

2. Choose the Correct Stub Options

Option	What the stub advertises	Typical use
`connected`	Connected routes selected by EIGRP	Branch LANs
`summary`	Locally configured summaries	Compact branch advertisement
`static`	Eligible static routes	Small local static destinations
`redistributed`	Redistributed routes	Controlled edge redistribution
`receive-only`	No routes from the stub	Learning-only special case

receive-only is exclusive. Do not combine it with route-advertisement options.

3. Configure Stub Routing in Classic Mode

Branch R3

router eigrp 100
 network 10.0.23.3 0.0.0.0
 network 10.30.0.0 0.0.255.255
 passive-interface GigabitEthernet0/1
 eigrp stub connected summary

First verification

show ip eigrp neighbors detail
show ip protocols
show ip eigrp topology

The upstream neighbor should report R3 as a stub peer. The branch LAN remains advertised because it is selected by EIGRP.

4. Configure Stub Routing in Named Mode

router eigrp BRANCH
 address-family ipv4 unicast autonomous-system 100
  network 10.0.23.3 0.0.0.0
  network 10.30.0.0 0.0.255.255
  eigrp stub connected summary
  af-interface GigabitEthernet0/1
   passive-interface
  exit-af-interface
 exit-address-family

Learning tip: The behavior is the same. Named mode groups address-family and interface settings under one process.

5. Follow a Query Before and After Stub

Successor fails

The upstream router has no feasible successor.

Route goes Active

DUAL asks relevant non-stub neighbors for a path.

Stub boundary helps

The branch is excluded from needless transit Queries.

This reduces work and can lower the chance of delayed Replies in a large hub-and-spoke design. It does not repair packet loss or a broken control plane.

6. Advertise an Exception with a Leak Map

A leak map can allow selected routes that the normal stub choice would suppress. Use it only when a clear policy requires an exception.

ip prefix-list STUB-EXCEPTION permit 10.30.50.0/24
route-map STUB-LEAK permit 10
 match ip address prefix-list STUB-EXCEPTION
router eigrp 100
 eigrp stub connected summary leak-map STUB-LEAK

Platform check: Syntax and feature support vary by IOS release. Validate against the target device before deployment.

7. Verify the Control Plane and Routes

Peer capability

show ip eigrp neighbors detail

Confirm the upstream sees the stub flag.

show ip eigrp topology

Confirm only intended routes leave the branch.

Reachability

show ip route eigrp

Confirm the branch still learns remote routes.

8. Troubleshoot Common Stub Mistakes

Symptom	Likely cause	Check
Branch LAN missing upstream	Wrong stub option or network selection	`show ip protocols`
Stub still receives a Query	It may be the destination owner or design differs	Inspect prefix and neighbor detail
Transit path disappeared	Stub used on a transit router	Recheck topology role
Unexpected external advertised	`redistributed` option enabled	Review stub and redistribution policy

9. Guided Practice Lab

Baseline

Form neighbors without stub.
Record branch routes.
Capture neighbor detail.

Enable stub

Use connected and summary.
Confirm the upstream stub flag.
Compare advertised routes.

Create a safe failure

Fail a core route in an isolated lab.
Observe the Active process.
Explain why the branch is not queried.

10. Build an Advertisement Plan Before Choosing Options

Write down every route the branch owns and classify its source. Then select only the stub keywords required to advertise those routes.

Branch requirement	Stub choice	Validation
Advertise directly connected user LANs	`connected`	Confirm each LAN is selected by EIGRP.
Advertise one compact site prefix	`summary`	Confirm component routes remain reachable.
Advertise an approved static service route	`static`	Confirm the static route and platform eligibility.
Advertise a redistributed local protocol	`redistributed`	Use prefix policy, metric, and tagging.
Advertise nothing from the branch	`receive-only`	Verify the upstream learns no branch prefix.

Design rule: Select options from business reachability requirements, not from a desire to make the routing table as small as possible.

11. Understand the Receive-Only Special Case

A receive-only stub learns routes from its neighbor but advertises no routes of its own. It is exclusive and should not be combined with connected, summary, static, or redistributed options.

router eigrp 100
 eigrp stub receive-only

This is uncommon for a normal branch because a branch usually needs to advertise at least one LAN. Use it only when the design explicitly needs a learning-only EIGRP participant.

Expected result: If the upstream loses the branch prefixes after enabling receive-only, the command is behaving as designed—not malfunctioning.

12. Design Stub Routing for Multiple Branches

Classify the site

Confirm the branch is non-transit and identify every exit.

Choose advertisements

Use connected, summary, or approved exceptions only.

Test failures

Fail primary and backup links and observe route plus Query behavior.

Dual-homed branches may still be stubs when they are not intended to carry traffic between hubs. Test both failure directions because each hub must understand the stub capability and valid branch advertisements.

13. Use a Safe Stub Change Workflow

Capture neighbor details, topology entries, routing tables, and advertised branch prefixes.
Confirm the router is not an intentional transit path.
Configure the smallest set of stub options that meets the advertisement plan.
Verify the upstream neighbor reports the stub capability.
Test every branch prefix and its return path.
Introduce one isolated failure and compare the Query scope with the baseline.
Document rollback commands and final output.

14. Practice ENARSI-Style Decision Scenarios

Scenario	Best interpretation	Action
A branch needs only connected LANs and one summary	Normal non-transit site	Use connected and summary.
A branch redistributes a local static service	Default stub options may omit it	Add an approved static option or controlled leak policy.
Two core routers use the branch as backup transit	Simple stub behavior conflicts with design	Redesign transit or do not mark it stub.
Queries still cross a summarized core boundary	Summary placement or component visibility is wrong	Inspect the advertising interface and topology.
Neighbor is up but one branch prefix is missing	Adjacency is healthy; advertisement selection is wrong	Check route source, stub options, and network selection.

15. Frequently Asked Questions

Does an EIGRP stub router receive routes?

Yes. Stub primarily controls advertisements and Query behavior; it can still learn routes from neighbors.

Does passive-interface make a router a stub?

No. Passive mode stops Hellos on one interface. Stub is a router capability advertised to EIGRP neighbors.

Is stub routing the same as route filtering?

No. Stub routing also changes Query behavior. Route filtering controls route acceptance or advertisement.

Why are connected and summary commonly used together?

They let a branch advertise its selected connected networks and any deliberate summaries without acting as general transit.

Can a dual-homed branch be an EIGRP stub?

Yes, when it is not intended to provide transit between its upstream neighbors. Test reachability through both links.

Does stub routing stop every Query?

No. It limits Queries that would treat the stub as a possible transit path. Always verify behavior for the exact prefix and topology.