Situation

# EIGRP建立neighbor加上認證機制
EIGRP neighbor establishment requires an authentication mechanism.

Configuration - Key chain

[R1]
conf t
  router eigrp 300
    network 172.17.0.0

  key chain "NAME"
    key 1
      key-string "KEY_STRING"
      cryptographic-algorithm hmac-sha-256
  
  interface ether 0/1
    ip address 172.17.89.9 255.255.255.0
    ip authentication mode eigrp 300 md5
    ip authentication key-chain eigrp 300 "NAME"

[R2]
conf t
  router eigrp 300
    network 172.17.0.0

  key chain "NAME"
    key 1
      key-string "KEY_STRING"
      cryptographic-algorithm hmac-sha-256
  
  interface ether 0/1
    ip address 172.17.89.8 255.255.255.0
    ip authentication mode eigrp 300 md5
    ip authentication key-chain eigrp 300 "NAME"

Check

# 檢查neighbor
show ip eigrp neighbor

# 檢查密碼，小心空白
show key chain