Problems With Dhcp Snooping - Cisco Nexus 1000V Troubleshooting Manual

Chapter 19 DHCP, DAI, and IPSG
S e n d d o c u m e n t c o m m e n t s t o n e x u s 1 k - d o c f e e d b a c k @ c i s c o . c o m .

Problems with DHCP Snooping

The following are symptoms, possible causes, and solutions for problems with DHCP snooping.
Symptom Possible Causes
With snooping IP address was not added to binding database.
configured, DHCP
Faulty connection between DHCP server and
client is not able to
client.
obtain an IP address
from the server.
The interface of the DHCP server(s) connected
to the DVS as a VM is not trusted.
DHCP requests from the VM are not reaching
the server for acknowledgement.
DHCP requests and acknowledgements are not
reaching the Cisco Nexus 1000V.
The Cisco Nexus 1000V is dropping packets.
OL-28795-01
Solution
Verify the connection between the DHCP
1.
server(s) and the host connected to the client.
vmkping
If the connection between DHCP server and the
2.
host is broken, do the following:
Check the configuration in the upstream
–
switch, for example, verifying that the
VLAN is allowed, etc.
Make sure the server itself is up and
–
running.
1. On the VSM, verify that the interface is trusted.
show ip dhcp snooping
2. On the VSM, verify the vEthernet interface
attached to the server is trusted.
module vem mod# execute vemcmd show
dhcps interfaces
On the DHCP server, log in and use a packet capture
utility to verify requests and acknowledgements in
packets.
From the client vEthernet interface, SPAN the
•
packets to verify they are reaching the client.
On the host connected to the client, enable VEM
•
packet capture to verify incoming requests and
acknowledgements in packets.
On the VSM, verify DHCP statistics.
show ip dhcp snooping statistics
module vem mod# execute vemcmd show
dhcps stats
Cisco Nexus 1000V Troubleshooting Guide, Release 4.2(1)SV2(2.1)
Problems with DHCP Snooping
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