DHCP issue after stack replacement

[michaelpatton]

I recently completed a switch replacement under the MS225 replacement action. Six switches broken in to two stacks of 3 each. Since the replacement, about a half dozen endpoints will not get a good IP address via DHCP. I've confirmed that the ports they are on are assigned to the correct VLAN, and they will connect if manually assigned an IP address. Clients are a mix of Windows 7 and Windows 10. I have tried all of the Windows troubleshooting tricks that I know of (netsh int ip reset, netsh winsock reset, ipconfig /release and /renew) and they still won't get anything from DHCP except for an APIPA IP address. If anyone has any thoughts or suggestions on what could be causing this, I'd love any help anyone can provide.

Thank you!

[NolanHerring]

Validate trunking between stacks and your core is allowing the correct VLANs etc.

Where is your DHCP server running?

[PhilipDAth]

What is acting as the DHCP server?

Are you using the switch security service that restricts DHCP servers, or any other switch security features?

[michaelpatton]

There are two devices acting as DHCP servers on the network. An MS250-48FP Layer 3 switch acting as DHCP server for VLANs 1 and 200, and an MX84 acting as DHCP server for VLANs 500 and 50.

[PhilipDAth]

Are the issues happening with both DHCP servers?

[michaelpatton]

Issues are only with the Layer 3 switch providing DHCP, and I believe only on VLAN 1 (I don't remember any on VLAN 200).

[PhilipDAth · Accepted solution]

Is there plenty of free IP addresses in the DHCP server? 

Anything in the event log on the switch acting as the DHCP server? 

[michaelpatton]

Looks like you hit the nail on the head, @PhilipDAth. The DHCP server reports 257 IP addresses assigned in our .0/24 range. Looks like some of our VoIP phones got assigned to the wrong VLAN during the switch over, which used up the rest of the IP range. 

[NolanHerring]

Glad you figure it out.

If I were you, I would enable the email alert for DHCP Pool Exhaustion so in the future you know before hand 😃