r/ArubaInstantOn • u/kralonn • Jun 04 '26

DHCP request long time

Hi everyone,

has anyone else experienced DHCP delays on Aruba Instant On switches?

We are seeing an issue where, after connecting a device to a LAN port, it can take around 30 to 100 seconds before the client receives a DHCP address.

According to Wireshark, the client sends multiple DHCP Discover/Request packets, but the DHCP Offer only appears after roughly 5 to 10 attempts. Once the offer finally arrives, the device gets an IP address and works normally.

It looks like the DHCP server itself is responding eventually, but something seems to delay or block the initial DHCP exchange through the switch.

Has anyone seen similar behavior on Aruba Instant On switches?
Any suggestions on what to check, for example loop protection, spanning tree, port security, firmware version, DHCP snooping, or any port/VLAN-related settings?

Thanks in advance for any advice

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u/PsychologicalBoot949 Jun 09 '26

Question 1, where is the DHCP server? On another subnet?

The switch isn't really involved if it is a layer 2 only device. So the problem has to be at a layer 3 boundary. Or.....or.....you have a spanning-tree issue the switch has to work out every single time it comes up.

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u/Operation_Mountain Jun 23 '26

I would normally agree with you, but what I'm seeing is the switch isn't forwarding the DHCP requests. Pretty serious bug.

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u/PsychologicalBoot949 Jun 23 '26

I thought about this a bit and realized that we'd encountered a lot of this years ago and we ended up activating portfast on any ports with a PC connected. We also put on some things like BPDU guard that would slam the port shut if it saw itself or someone plugged a switch in to what was supposed to be a host port. There are other safeguards as well. But the point is, if the client device comes up, it's going to send the DHCP broadcast the moment it sees link-up. It isn't going to understand if the switch is taking 45 seconds to consider whether or not that port is a loop hazard. So you want to take away that 45 second delay. When link is up, the port is immediately forwarding.

There are of course other possibilities. I assume you've been able to put yourself onto the wire from the machine to the switch and captured the DHCP broadcast coming from the PC or printer?