R1#sh run | b key
key chain Prob3
 key 1
  key-string bosco
!
interface Ethernet0/1
 ip address 17.57.100.1 255.255.255.0
 ip authentication mode eigrp 100 md5
 ip authentication key-chain eigrp 100 Prob3
 half-duplex
!


S6#sh run | b key
key chain Prob3
 key 1
  key-string bosco
!
interface Vlan16
 ip address 17.57.100.2 255.255.255.0
 ip authentication mode eigrp 100 md5
 ip authentication key-chain eigrp 100 Prob3
!
router eigrp 100
 network 17.57.100.2 0.0.0.0
 network 17.57.101.1 0.0.0.0
 network 17.57.102.1 0.0.0.0
 network 17.57.103.1 0.0.0.0
 no auto-summary
!