We have begun using the new generation of 3850 switches, specifically WS-C3850-24P-P switches. We use the switch to supply DHCP for the VLANs.
We are running software version:
cat3k_caa-universalk9, version 03.03.00SE
So, we built the pool according to these guidelines:
ip dhcp excluded-address 10.96.81.200 10.96.81.209
ip dhcp excluded-address 10.96.81.220 10.96.81.254
ip dhcp excluded-address 10.96.81.1 10.96.81.12
ip dhcp excluded-address 10.96.81.30 10.96.81.50
ip dhcp pool LEGACY-DATA
network 10.96.81.0 255.255.255.0
dns-server 10.1.1.10 10.96.200.11
So, here is the kicker... users are not getting addresses. The dhcp server doesn't respond BUT... it responds to a certain point. Immediately after restarting the DHCP service on teh switch, this is what the pool statistics show:
Pool LEGACY-DATA :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 254
Leased addresses : 0
Excluded addresses : 148
Pending event : none
1 subnet is currently in the pool :
Current index IP address range Leased/Excluded/Total
10.96.81.13 10.96.81.1 - 10.96.81.254 0 / 148 / 254
According to my math, there are 54 exclusions. The pool shows 148 before any leases handed out, and as each lease is handed out, the excluded rises. I know the older version of this new Cat-os had DHCP issues... does this version as well?
Any suggestions? Our pool appears to run out of leases iwth about 100 leased, showing 106 leased, 148 excluded, for a total of 254... which sounds right, but there are only 54 excluded.
Not that this will resolve the issue you have, but not sure how you came up with 54 exclusions.
10.96.81.200 10.96.81.209 10 addresses
10.96.81.220 10.96.81.254 35 addresses
10.96.81.1 10.96.81.12 12 addresses
10.96.81.30 10.96.81.50 21 addresses
Try to decrease you lease time from defat of 1 day and stop and stop and start your dhcp server
Please don't forget to rate any posts that have been helpful.
Well, I appreciate the suggestion, but that doesn't work.
We have decreased to 1 day (the default) and the problem recurs. DHCP settings don't go less than that on the switch (to my knowledge) The only way to fix it is to reboot the switch or stop and start the dhcp service, but the problem recurs. It takes about 48 horus before addresses are exhausted, then it won't hand any more out, even though a number of them are expired.
Thanks again for the suggestion,
I also have same DHCP issue with cisco 3850 48 TDL switches, we have Per VLAN basis DHCP Pool and some Ip address have bind with users device Mac-address. The DHCP issue is so frustrating and irritating, when it occur i have to manually clear ip dhcp bindings and then i have to manually restart the DHCP process by deleting that pool and recreating.
Please guide me over this issue.
I have attached the switch configuration.
Curious to what was he lease time set before you decreased.it to a day?
FYI - Dhcp Lease time defaults
to 1day but this can be changed
Below config changes.lease.times.to 8 hours
ip dhcp pool LEGACY-DATA
Lease 0 8 0
Sent from Cisco Technical Support Android App