1.0 Network Infrastructure and Connectivity

DHCPv4 Troubleshooting Practice Questions

Updated for CCNA v2.0

Client, server, and relay faults on IOS devices, including snooping and pool exhaustion.

CCNA v2.0 objective 1.7 · objective map

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One solved question, so you can see how these are marked

In what order do the messages of a normal DHCPv4 exchange occur?

Discover, Offer, Request, Acknowledge

The client broadcasts a Discover, a server answers with an Offer, the client sends a Request for that offer, and the server confirms with an Acknowledge.

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All 10 DHCPv4 Troubleshooting questions in this set

Answers and explanations appear when you work through the set above.

A DHCP server is on a different subnet than the clients. Which command on the client-facing router interface lets the clients' broadcasts reach it?
- ip helper-address 10.1.1.10
- ip dhcp relay client 10.1.1.10
- ip forward-protocol udp 10.1.1.10
- dhcp server 10.1.1.10
Where must ip helper-address be applied?
- On the interface facing the DHCP clients
- On the interface facing the DHCP server
- On the console line
- Under the DHCP pool
Which command displays the addresses a router's DHCP server has leased and the associated client identifiers or hardware addresses?
- show ip dhcp binding
- show ip dhcp pool
- show ip dhcp server statistics
- show dhcp lease
Clients in a subnet get an address that another host is already using. Which IOS DHCP server setting prevents leasing addresses of statically configured devices?
- ip dhcp excluded-address
- ip dhcp pool default-router
- lease infinite
- ip dhcp snooping trust
All addresses in a router's DHCP pool are leased and new clients receive APIPA addresses. What does 'show ip dhcp pool' most likely show?
- Leases, exclusions and conflicts account for every address in the pool
- Zero total addresses
- A default router of 0.0.0.0
- An infinite number of free addresses
Which UDP ports does DHCPv4 use?
- Server 67 and client 68
- Server 53 and client 54
- Server 69 and client 70
- Server 161 and client 162
DHCP snooping is enabled on a switch, and clients on VLAN 20 cannot get an address. The DHCP server is behind the uplink port. What is a likely cause?
- The uplink toward the server is not configured as a trusted port
- The access ports are trusted
- PortFast is enabled on the access ports
- The VLAN is using an IPv6 prefix
A client leases an address from a router's DHCP pool but has no default gateway. Which pool command is missing?
- default-router
- dns-server
- domain-name
- network
Clients in VLAN 20 receive 169.254.x.x addresses. The DHCP server is a router in another subnet. An AI assistant notes that interface Vlan20 has no ip helper-address and recommends adding one that points at the server. Before you accept it, what is the most useful thing to verify?
- That the server has a pool for the VLAN 20 subnet and a route back to the Vlan20 SVI address
- That the helper address is configured on the server's interface rather than on the SVI
- That DHCP snooping is disabled globally, since it blocks relayed requests by default
- Nothing further, because a recommendation that quotes the running config needs no checks
show ip dhcp conflict lists 10.1.20.5 through 10.1.20.9, which are statically addressed printers. An AI assistant recommends running clear ip dhcp conflict * to reclaim the addresses. What is the better fix?
- Run the command as suggested, since clearing conflicts permanently frees the addresses
- Shrink the pool's network statement so that the printers fall outside its subnet mask
- Disable ping-based conflict detection so that the addresses are no longer flagged
- Exclude the printer range with ip dhcp excluded-address, then clear the conflicts