DHCP Lease Time

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L1 Bithead

DHCP Lease Time

Hi
We are distributing dhcp with mac reserve on paloalto. rental period is 10 minutes. is this time too short? Does the system get tired because the time is short?

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Cyber Elite

@Aykut1,

That is an incredibly short lease time, and not something I personally would recommend just because it's causing a needless amount of traffic. That short of a lease time is generally compensating for not having enough available IPs. With that being said, the system isn't going to be overwhelmed solely because you have a short lease time. That is all going to boil down to the number of requests the system is getting at any one time. 

I kind of highly doubt this short of a lease time would legitimately cause any issues in an environment small enough to be utilizing the built-in DHCP capabilities of the firewall. 

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L1 Bithead

So you think you can tire the system? Because it is a reserved IP when the lease expires, it gets the same IP again. does it still tire the system?

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Cyber Elite

@Aykut1,

Under realistic operations, I wouldn't believe that you are going to overload the system by setting a 10 minute DHCP lease time unless you have a huge number of clients constantly checking renewing their lease. With that being said, anybody who actually had more then even a hundred clients is really unlikely to utilize the built-in DHCP server on their firewall. We're talking about thousands, if not tens of thousands, of clients before I would expect this to actually cause an issue dependent on platform.

 

Keep in mind that the fact that you have reserved IPs configured literally does nothing to depress the DHCP request process. You still have clients renewing constantly because the lease time is every 10 minutes. The only thing that reserving an IP does is tells the firewall that this MAC address is always going to get this IP address. The client/server communication for those DHCP requests doesn't change at all when compared to a reserved client versus a normal DHCP client.

I still think that 10 minutes for a DHCP lease time is incredibly short, and I can't think of any true reason to ever have such a short lease time configured. You're causing needless DHCP renewals to cross your network by setting your lease time that low. If this is for a wireless network you're waisting a lot of airtime simply on DHCP renewal requests. What exactly is driving you to configure your lease time at 10 minutes?

L1 Bithead

Understood thanks. You say you are exhausting the system. Is there a document or an article about it?

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