实验过程：
第一步  R1、R2预配置
R1(config)#int s2/1
R1(config-if)#ip add 192.168.0.1 255.255.255.0
R1(config-if)#no sh
R1(config-if)#exit

R2(config)#int s2/1
R2(config-if)#ip add 192.168.0.2 255.255.255.0
R2(config-if)#no sh
R2(config-if)#exit

第二步  在R1、R2上配置Eigrp
R1(config)#router eigrp 100
R1(config-router)#net 192.168.0.0
R1(config-router)#exit

R2(config)#router eigrp 100
R2(config-router)#net 192.168.0.0
R2(config-router)#exit

第三步  确认R1与R2成为Eigrp邻接关系
R1#show ip eigrp neighbors
IP-EIGRP neighbors for process 100
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.0.2             Se2/1             11 00:02:46  104   624  0  3

第四步  配置R1、R2的认证密码
R1(config)#key chain Eigrp-Key
R1(config-keychain)#key 1
R1(config-keychain-key)#key-string norvel.com.cn
R1(config-keychain-key)#exit

R2(config)#key chain Eigrp-Key
R2(config-keychain)#key 1
R2(config-keychain-key)#key-string norvel.com.cn
R2(config-keychain-key)#exit

第五步  确认Key的配置
R1#show key chain
Key-chain Eigrp-Key:
    key 1 -- text "norvel.com.cn"
        accept lifetime (always valid) - (always valid) [valid now]
        send lifetime (always valid) - (always valid) [valid now]

第六步  配置R1、R2的认证
R1#conf t
R1(config)#int s2/1
R1(config-if)#ip authentication key-chain eigrp 100 Eigrp-Key
R1(config-if)#ip authentication mode eigrp 100 md5

R2(config)#int s2/1
R2(config-if)#ip authentication key-chain eigrp 100 Eigrp-Key
R2(config-if)#ip authentication mode eigrp 100 md5

第七步  查看Eigrp接口信息
R1#show  ip eigrp interfaces detail
IP-EIGRP interfaces for process 100

                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Se2/1              1        0/0       108       0/15         511           0
  Hello interval is 5 sec
  Next xmit serial <none>
  Un/reliable mcasts: 0/0  Un/reliable ucasts: 2/9
  Mcast exceptions: 0  CR packets: 0  ACKs suppressed: 6
  Retransmissions sent: 0  Out-of-sequence rcvd: 0
  Authentication mode is md5,  key-chain is "Eigrp-Key"
  Use unicast

第八步  调试Eigrp包
R1#debug eigrp packets
EIGRP Packets debugging is on
    (UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB, SIAQUERY, SIAREPLY)
R1#
*Jul  1 17:21:30.835: EIGRP: Sending HELLO on Serial2/1
*Jul  1 17:21:30.835:   AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0
*Jul  1 17:21:31.631: EIGRP: received packet with MD5 authentication, key id = 1
*Jul  1 17:21:31.631: EIGRP: Received HELLO on Serial2/1 nbr 192.168.0.2
*Jul  1 17:21:31.631:   AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
R1#
*Jul  1 17:21:35.243: EIGRP: Sending HELLO on Serial2/1
*Jul  1 17:21:35.243:   AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0