Command of the Day

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Guru Elite
Posts: 20,418
Registered: ‎03-29-2007

COTD: Why is my client NOT getting a DHCP address?

Why is my client not getting a DHCP address? Is my DHCP server misconfigured? Is my client even in the right VLAN? Is my client even requesting a DHCP address?

First things first: Is my client in the right VLAN? the "show user-table verbose" command will show the client's role (very important) as well as the VLAN the client is placed in, in parentheses all the way to the right. (you should maximize your terminal screen, because there are plenty of colums):
(m3.arubanetworks.com) #show user-table verbose

Users
-----
IP MAC Name Role Age(d:h:m) Auth VPN link AP name Roaming Essid/Bssid/Phy Profile Forward mode Server Vlan Bwm
---------- ------------ ------ ---- ---------- ---- -------- ------- ------- --------------- ------- ------------ ------ ---- ---

10.69.17.151 00:21:6a:7f:4a:be cjoseph test1-staff-split 00:02:56 802.1x colin-ap93 Associated(Remote) ethersphere-wpa2/00:24:6c:fc:1b:f1/a-HT aruba-split-aaa-profile split tunnel test1-supersvr 1001 (1001)
10.69.17.150 00:1b:63:f0:42:38 cjoseph test1-staff-split 00:00:41 802.1x cjoseph-rap5f Associated(Remote) ethersphere-wpa2/00:1a:1e:40:96:c1/a-HT aruba-split-aaa-profile split tunnel test1-supersvr 1001 (1001)
10.69.17.167 00:21:6a:64:e1:b6 ARUBANETWORKS\cjoseph2 test1-staff-split 00:11:33 802.1x cjoseph2-rap5 Associated(Remote) ethersphere-wpa2/00:1a:1e:40:0b:11/a-HT aruba-split-aaa-profile split tunnel test1-supersvr 1001 (1001)

User Entries: 3/3


So I can see that my client is in VLAN 1001, just like I wanted it to, but I want to see if my DHCP server is giving out addresses, and if the client is requesting addresses, like it should. So I turn on logging by executing:

config t
logging level debug network subcat dhcp


After that I should be able to see the DHCP trail for a user, EVEN if the controller is NOT the DHCP server on the network, by executing " show log network all | include "

(m3) #        show log network all | include  00:1a:1e:c0:24:0a
Jul 15 17:14:36 :202534: |dhcpdwrap| |dhcp| Datapath vlan1: DISCOVER 00:1a:1e:c0:24:0a
Jul 15 17:14:36 :202546: |dhcpdwrap| |dhcp| Datapath vlan1: OFFER 00:1a:1e:c0:24:0a clientIP=192.168.1.43
Jul 15 17:14:36 :202541: |dhcpdwrap| |dhcp| Received DHCP packet from Datpath, sos msg hdr flags 0x42 opcode 0x5a ingress 0x1023 vlan 1 egress 0x1 src mac 00:1a:1e:c0:24:0a
Jul 15 17:14:36 :202536: |dhcpdwrap| |dhcp| Datapath vlan1: REQUEST 00:1a:1e:c0:24:0a reqIP=192.168.1.43
Jul 15 17:14:36 :202544: |dhcpdwrap| |dhcp| Datapath vlan1: ACK 00:1a:1e:c0:24:0a clientIP=192.168.1.43

The DISCOVER is the initial DHCP packet that a client will issue upon link UP
The OFFER is what the client gets Offered by the DHCP server
The REQUEST is when the client signals that it wants to choose an IP address
The ACK is the DHCP server ACKnowledging to the client, that it can have that address.


Colin Joseph
Aruba Customer Engineering

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