EIGRP — ip summary-address eigrp per-interface

Routing
Intermediate
10 min
2 steps
Cisco IOS-style

Three routers in a chain run EIGRP AS 100. R1 has three /24 loopbacks under a /16 cover. Configure ip summary-address eigrp 100 10.0.0.0 255.255.0.0 on R1's uplink so R2 learns one /16 entry instead of three /24s.

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Free · no install · no account

Scenario

EIGRP route summarisation is per-interface. The ip summary-address eigrp <ASN> <prefix> <mask> command tells EIGRP "when advertising out this interface, replace anything in this range with one summary route." Compare to OSPF, where summarisation is configured on the ABR per-area (area X range); EIGRP is flat (no areas), so the granularity is the egress interface. In this lab R1 advertises three /24s as components of 10.0.0.0/16. With summarisation on Gi0/0, R2 sees one /16 instead of three /24s.

Topology

2 × router · Cisco IOS-style

R1 — router
R2 — router

What you will do

On R2, run show ip route eigrp. Confirm three /24s (10.0.0.0/24, 10.0.1.0/24, 10.0.2.0/24) are present.
On R1, apply ip summary-address eigrp 100 10.0.0.0 255.255.0.0 to Gi0/0 (the link to R2).

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