Cisco switch. PC not getting DHCP lease on 10G port

weust

Active Member
Aug 15, 2014
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I have a Cisco ws-c3560cx-8xpd-s switch which has 6 1GbE ports, 2 Multi-Gig ports and 2 SFP+ ports.

On the second Multi-Gig ports I connected my desktop using a Mellanox ConnectX-3 with a SFP-RJ45 module.
The desktop is running Windows 10, but can't get a DHCP lease.
Setting is manually works, but be able to use DHCP would be preferred.

On one of the 1GbE ports I have my PlayStation 4 Pro which receives a DHCP lease just fine.

Blow is the config for both ports. As you can see I only added a description.
I'm not using any VLAN tagging in my network, so everything uses VLAN 1.

interface GigabitEthernet1/0/4
description PS4 Pro
!

interface TenGigabitEthernet1/0/8
description Desktop
!
I can't find anything only regarding this issue.
All I can imagine is that it being a Multi-Gig ports that for some reason DHCP packets aren't forwarded in the switch?

Can anyone shed a light on this?
 

j_h_o

Active Member
Apr 21, 2015
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California, US
Where is your DHCP server configured? Can you describe that configuration?

And if you move your Windows 10 machine to another 1G port, with no other changes, does it get DHCP successfully?
 

weust

Active Member
Aug 15, 2014
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The first two ports of the Cisco are a port-channel to a Ubiquiti 24 port switch (LACP aggregate).
The third is my OPNsense LAN port, the fourth the PS4 Pro.
Ports five and six are a another LACP port-channel to a server used for iSCSI (totally overkill as it's used for Unifi Video with only one camera at a max of 100MBps).

The first Multi-Gig port isn't used, then the Desktop one.
SFP+ ports are used for two servers. One for VM connectivity (one SAN, just network), and one for ZFS share access.

The Ubiquiti switch it mainly used for server management and iDRAC/IPMI, Access Point/camera/8 port Ubiquiti swith all with POE.

Route wise, the Desktop on Te1/0/8 will go through the port-channel on the first two ports, to the management aggregate (Dell R230) on the Ubiquiti 24 port switch to a FreeBSD jail running the DHCP server.


I will try the Desktop on the PS4 Pro port, as all other 1G ports are used.
 

weust

Active Member
Aug 15, 2014
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This is odd. Switching the port works fine. Using ipconfig /release and /renew to really force it just works fine.
A lease is picked up immediately.

Switching it back to the Multi-Gig ports works fine too all of a sudden.

So I did another ipconfig /release and rebooted the desktop.
Doing the /release doesn't make sense of course, but can't hurt either.

This time it takes a bit longer to get the lease, but it does work.

It makes me think it's a driver quirk thingy.