EIGRP

Enhanced Interior Gateway Routing Protocol metrics, named mode configuration, and convergence tuning.

EIGRP Named Mode Configuration

Named mode (ENCOR preferred) — all config under a single named instance; replaces classic mode

configure terminal
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  network 10.50.1.0 0.0.0.255
  network 10.50.2.0 0.0.0.255
  eigrp router-id 1.1.1.1
  af-interface default
   passive-interface
  exit-af-interface
  af-interface GigabitEthernet0/0/0
   no passive-interface
  exit-af-interface
 exit-address-family
end

Classic mode — still appears on older devices; network statements with wildcard mask

configure terminal
router eigrp 100
 network 10.50.1.0 0.0.0.255
 eigrp router-id 1.1.1.1
 passive-interface default
 no passive-interface GigabitEthernet0/0/0
end

EIGRP Neighbor Verification

Show EIGRP neighbors — H (handle), hold timer, uptime, SRTT, Q count (should be 0)

show ip eigrp neighbors
show ip eigrp neighbors detail

EIGRP Topology Table

Show EIGRP topology — successor (S), feasible successor (FS), FD, RD, and metric

show ip eigrp topology
show ip eigrp topology all-links
show ip eigrp topology 10.50.1.0/24

EIGRP Interface Verification

Show EIGRP-enabled interfaces — peers, pending routes, mean SRTT

show ip eigrp interfaces
show ip eigrp interfaces detail

K Values (Metric Composition)

Default K values — K1=1 (bandwidth), K2=0 (load), K3=1 (delay), K4=0 (reliability), K5=0; K values must match for adjacency

show ip protocols | section eigrp
! Default metric: 256 * ((10^7 / min-bandwidth) + cumulative-delay)

Modify metric weights — named mode; rarely changed but exam-relevant

configure terminal
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  metric weights 0 1 0 1 0 0 0
 exit-address-family
end

Unequal-Cost Load Balancing

Variance — multiplier applied to FD; routes with metric < (FD * variance) are used for load balancing via feasible successors

configure terminal
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  topology base
   variance 2
  exit-af-topology
 exit-address-family
end

Classic mode variance

configure terminal
router eigrp 100
 variance 2
end

Verify unequal-cost paths in routing table

show ip route eigrp
show ip eigrp topology

Stub Routing

EIGRP stub — advertises only specified route types; reduces query scope; critical for hub-and-spoke

configure terminal
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  eigrp stub connected summary
 exit-address-family
end

Stub options — connected, summary, static, redistributed, receive-only

! receive-only — does not advertise any routes; only receives
configure terminal
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  eigrp stub receive-only
 exit-address-family
end

Verify stub status

show ip eigrp neighbors detail | include Stub
show ip protocols | section eigrp

Summarization

Manual summarization on an interface — named mode; suppresses component routes, installs Null0 discard route

configure terminal
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  af-interface GigabitEthernet0/0/0
   summary-address 10.50.0.0 255.255.0.0
  exit-af-interface
 exit-address-family
end

Leak-map — advertise summary AND specific component routes that match

configure terminal
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  af-interface GigabitEthernet0/0/0
   summary-address 10.50.0.0 255.255.0.0 leak-map LEAK-SPECIFIC
  exit-af-interface
 exit-address-family
end

Authentication

MD5 authentication — named mode; key chain must exist

configure terminal
key chain EIGRP-KEYS
 key 1
  key-string <key-string>
!
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  af-interface GigabitEthernet0/0/0
   authentication mode md5
   authentication key-chain EIGRP-KEYS
  exit-af-interface
 exit-address-family
end

HMAC-SHA-256 authentication — named mode; stronger alternative

configure terminal
key chain EIGRP-KEYS
 key 1
  key-string <key-string>
  cryptographic-algorithm hmac-sha-256
!
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  af-interface GigabitEthernet0/0/0
   authentication mode hmac-sha-256 EIGRP-KEYS
  exit-af-interface
 exit-address-family
end

Redistribution

Redistribute OSPF into EIGRP — must specify seed metric (bandwidth, delay, reliability, load, MTU)

configure terminal
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  topology base
   redistribute ospf 1 metric 10000 100 255 1 1500
  exit-af-topology
 exit-address-family
end

Redistribute with route-map

configure terminal
router eigrp LAB
 address-family ipv4 unicast autonomous-system 100
  topology base
   redistribute ospf 1 route-map OSPF-TO-EIGRP metric 10000 100 255 1 1500
  exit-af-topology
 exit-address-family
end

Verification Summary

Key show commands for EIGRP troubleshooting

show ip eigrp neighbors
show ip eigrp topology
show ip eigrp interfaces
show ip route eigrp
show ip protocols | section eigrp