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DHCPPrivileged EXEC

show ip dhcp server statistics

Displays DHCP server statistics, including the number of messages sent and received, to monitor DHCP server performance and troubleshoot issues.

Syntax·Privileged EXEC
show ip dhcp server statistics

When to Use This Command

  • Check if the DHCP server is receiving DISCOVER messages from clients.
  • Monitor the number of successful OFFER and ACK messages to ensure clients are getting IP addresses.
  • Identify high rates of NAK messages indicating client configuration problems.
  • Troubleshoot DHCP server performance issues by checking message counts over time.

Command Examples

Basic DHCP Server Statistics

show ip dhcp server statistics
Memory usage         43324
Database agents      0
Automatic bind       0
Manual bind          0
Expired leases       0
Malformed messages   0

Message                   Received
BOOTREQUEST               0
DHCPDISCOVER             15
DHCPREQUEST              12
DHCPDECLINE              0
DHCPRELEASE              2
DHCPINFORM               0

Message                   Sent
BOOTREPLY                0
DHCPOFFER                15
DHCPACK                  10
DHCPNAK                  2

Memory usage: 43324 bytes used by DHCP process. Database agents: 0 (no external database). Automatic bind: 0 (no dynamic bindings). Manual bind: 0 (no static bindings). Expired leases: 0. Malformed messages: 0 (no errors). Received: BOOTREQUEST 0, DHCPDISCOVER 15 (clients requesting IP), DHCPREQUEST 12 (clients accepting offer), DHCPDECLINE 0, DHCPRELEASE 2 (clients releasing IP), DHCPINFORM 0. Sent: BOOTREPLY 0, DHCPOFFER 15 (offers sent), DHCPACK 10 (acknowledgements sent), DHCPNAK 2 (negative acknowledgements).

Statistics with High NAK Rate

show ip dhcp server statistics
Memory usage         43324
Database agents      0
Automatic bind       0
Manual bind          0
Expired leases       0
Malformed messages   0

Message                   Received
BOOTREQUEST               0
DHCPDISCOVER             20
DHCPREQUEST              18
DHCPDECLINE              0
DHCPRELEASE              1
DHCPINFORM               0

Message                   Sent
BOOTREPLY                0
DHCPOFFER                20
DHCPACK                  10
DHCPNAK                  8

This output shows a high number of DHCPNAK (8) compared to DHCPACK (10). This indicates that many DHCPREQUEST messages are being rejected, possibly due to duplicate IP address detection or client misconfiguration. The DHCP server is sending NAKs because the requested IP is not available or the client's subnet is incorrect.

Understanding the Output

The output is divided into two sections: memory and binding statistics, and message counts. The first section shows memory usage (should be stable), database agents (0 if not using external DB), automatic bindings (dynamic leases), manual bindings (static), expired leases (should be low), and malformed messages (should be 0). The second section shows received and sent messages. Key metrics: DHCPDISCOVER received indicates client requests; DHCPOFFER sent should match DISCOVERs; DHCPREQUEST received indicates clients accepting offers; DHCPACK sent should match REQUESTs; DHCPNAK sent indicates rejections (high NAKs indicate problems). Watch for high malformed messages (corruption) or mismatched counts (e.g., more OFFERs than DISCOVERs).

CCNA Exam Tips

1.

CCNA exam tip: High DHCPNAK counts often indicate duplicate IPs or client misconfiguration; know that NAKs are sent when the server cannot honor the request.

2.

CCNA exam tip: The 'Malformed messages' counter should be zero; non-zero values indicate packet corruption or attacks.

3.

CCNA exam tip: Compare DHCPDISCOVER received vs DHCPOFFER sent; they should be equal in a healthy network.

4.

CCNA exam tip: Remember that 'show ip dhcp server statistics' is in Privileged EXEC mode, not global config.

Common Mistakes

Mistake 1: Confusing DHCPACK with DHCPOFFER; OFFER is sent first, ACK is sent after REQUEST.

Mistake 2: Ignoring the 'Malformed messages' field; it can indicate network issues or rogue DHCP servers.

Mistake 3: Forgetting to clear statistics with 'clear ip dhcp server statistics' before troubleshooting; old data can mislead.

Related Commands

show ip dhcp binding

Displays the current DHCP binding table, showing which IP addresses have been leased to clients, along with their MAC addresses, lease expiration, and type of binding.

show ip dhcp conflict

Displays IP address conflicts detected by the DHCP server, helping administrators identify and resolve duplicate IP assignments on the network.

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