200-301: Cisco Certified Network AssociateDemo

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QuestionQ440

IP Services

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Refer to the exhibit. Which configuration enables DHCP addressing for hosts connected to interface FastEthernet0/1 on router R3?

  • A interface FastEthernet0/1ip helper-address 10.0.1.1!access-list 100 permit tcp host 10.0.1.1 eq 67 host 10.148.2.1
  • B interface FastEthernet0/1ip helper-address 10.0.1.1!access-list 100 permit udp host 10.0.1.1 eq 67 host 10.148.2.1
  • C interface FastEthernet0/0ip helper-address 10.0.1.1!access-list 100 permit host 10.0.1.1 host 10.148.2.1 eq bootps
  • D interface FastEthernet0/1ip helper-address 10.0.1.1!access-list 100 permit udp host 10.0.1.1 eq bootps host 10.148.2.1
Explanation

DHCP relay must be configured on the interface that receives the client broadcasts, so ip helper-address 10.0.1.1 belongs on FastEthernet0/1, the LAN interface for 10.148.2.0/24. Since ACL 100 is applied inbound on FastEthernet0/0, it must also allow the relayed DHCP server reply traffic coming from 10.0.1.1 to R3. DHCP uses UDP, and the server port is 67, identified in IOS as bootps, so the correct ACL entry is the UDP permit using bootps from the DHCP server to host 10.148.2.1.

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