HP Switches and DHCP Relay Settings

Started by deanwebb, April 03, 2018, 08:45:21 AM

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deanwebb

April 03, 2018, 08:45:21 AM
Hello, got a question... I've read in HP documentation that more than one DHCP relay can be defined on a Procurve switch. Whichever one responds first is the relay that handles the DHCP request. I'm working with someone who is telling me that adding a second relay results in no devices getting a DHCP request. I've asked for the config from the switch, but at the same time, I want to make sure that I read things correctly regarding multiple DHCP relays defined on a Procurve. Anyone here with HP switch experience want to comment on this?
Take a baseball bat and trash all the routers, shout out "IT'S A NETWORK PROBLEM NOW, SUCKERS!" and then peel out of the parking lot in your Ferrari.
"The world could perish if people only worked on things that were easy to handle." -- Vladimir Savchenko
Вопросы есть? Вопросов нет! | BCEB: Belkin Certified Expert Baffler | "Plan B is Plan A with an element of panic." -- John Clarke
Accounting is architecture, remember that!
Air gaps are high-latency Internet connections.

icecream-guy

#1
April 03, 2018, 11:32:58 AM
Quote from: deanwebb on April 03, 2018, 08:45:21 AM
Hello, got a question... I've read in HP documentation that more than one DHCP relay can be defined on a Procurve switch. Whichever one responds first is the relay that handles the DHCP request. I'm working with someone who is telling me that adding a second relay results in no devices getting a DHCP request. I've asked for the config from the switch, but at the same time, I want to make sure that I read things correctly regarding multiple DHCP relays defined on a Procurve. Anyone here with HP switch experience want to comment on this?

I do believe, and don't quote me on this, that the DHCP request is sent to all DHCP servers at the same time, and the one that responds first wins.

this is based on Cisco devices, I have not HP Procurve experience.
:professorcat:

My Moral Fibers have been cut.

deanwebb

#2
April 03, 2018, 11:53:07 AM
^ True, it works in the Cisco world and I've got hands-on success with that. The HP docs read like it works that way, as well, but this guy...
Take a baseball bat and trash all the routers, shout out "IT'S A NETWORK PROBLEM NOW, SUCKERS!" and then peel out of the parking lot in your Ferrari.
"The world could perish if people only worked on things that were easy to handle." -- Vladimir Savchenko
Вопросы есть? Вопросов нет! | BCEB: Belkin Certified Expert Baffler | "Plan B is Plan A with an element of panic." -- John Clarke
Accounting is architecture, remember that!
Air gaps are high-latency Internet connections.

icecream-guy

#3
April 03, 2018, 03:08:09 PM
...if that second server is over a slow link,  true, true, you'd never get an IP from it...
:professorcat:

My Moral Fibers have been cut.

SimonV

#4
April 03, 2018, 03:12:22 PM Last Edit: April 03, 2018, 03:13:57 PM by SimonV
Both DHCP servers should send a reply and the client will return the request for whatever came first.  Unless there's some fancy DHCP feature configured where the DHCP servers are in active/passive, or in some sort of weighted load balancing which is configured or behaving incorrectly. But that's already beyond the Procurve question, it should work with two helpers configured.

Can't you just blame the firewall, btw?

:notthefirewall:

deanwebb

#5
April 03, 2018, 04:12:14 PM
I work for a NAC company so, yes, I can blame the firewall.
Take a baseball bat and trash all the routers, shout out "IT'S A NETWORK PROBLEM NOW, SUCKERS!" and then peel out of the parking lot in your Ferrari.
"The world could perish if people only worked on things that were easy to handle." -- Vladimir Savchenko
Вопросы есть? Вопросов нет! | BCEB: Belkin Certified Expert Baffler | "Plan B is Plan A with an element of panic." -- John Clarke
Accounting is architecture, remember that!
Air gaps are high-latency Internet connections.
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