04-24-2020 01:30 PM
Hi Community,
I am using a WS-C3850-24S as a dhcp server to deploy other switches.
Now I noticed that the 3850 provides a new IP to the dhcp client when the client is reconnecting to the 3850.
In detail when I do a shut no shut on the SVI of the client (in this case a WS-C2960C-8PC-L) the clients gets a new IP.
Is this a normal behaviour? I don't think so.
Here are more details about the 3850:
WS-C3850-24S
03.06.05E
ip dhcp pool DHCP-ZTP-POOL
network 10.1.178.0 255.255.255.0
default-router 10.1.178.1
option 150 ip 10.1.178.5
lease 1
I expect that the DHCP client gets the same IP until the lease times out.
I would be happy about a hint or an idea how I can solve this issue.
Thanks
Sebastian
Solved! Go to Solution.
04-24-2020 02:29 PM
Try changing the lease options :
The lease command takes up to three options: lease days [hours] [minutes], with hours and minutes being optional. You can specify a maximum period of 365 days, 23 hours and 59 minutes, and a minimum of 1 second. The default is one day.
lease {days [hours] [minutes] | infinite} Example: Device(dhcp-config)# lease 30 |
(Optional) Specifies the duration of the lease. |
04-24-2020 01:57 PM
Hello,
Yes this is normal behavior for a Cisco device running a DHCP server. By default, the Cisco device has dhcp conflict logging enabled, which will keep a persistent database of the assigned IPs, and will assign a new IP with each new request. This is a default behavior. In the past I have ran into issues like this with IP phones exhausting the dhcp pool because I didn't turn of dhcp conflict logging. The feature is turned off with "no ip dhcp conflict logging".
This is a great article that explains this much better than I can :)
http://blog.ipspace.net/2007/08/dhcp-conflict-logging-true-story.html
Also here is a similar post just for more information.
https://community.cisco.com/t5/switching/no-ip-dhcp-conflict-logging/td-p/3028936
HTH,
Barry
04-24-2020 02:29 PM
Try changing the lease options :
The lease command takes up to three options: lease days [hours] [minutes], with hours and minutes being optional. You can specify a maximum period of 365 days, 23 hours and 59 minutes, and a minimum of 1 second. The default is one day.
lease {days [hours] [minutes] | infinite} Example: Device(dhcp-config)# lease 30 |
(Optional) Specifies the duration of the lease. |
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