DHCP lease time

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  1. teots's Avatar
    Posts : 222
    Windows 10 64 Bit Home Version 20H2
       #1

    DHCP lease time


    What is the best DHCP lease time ? I stick to the default setting which is 120 minutes. And what yours ?
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  2. syntoh's Avatar
    Posts : 40
    Windows 10 pro en
       #2
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  3. jimbo45's Avatar
    Posts : 10,484
    Windows / Linux : Arch Linux
       #3

    Hi there

    In general for Home networks this doesn't matter if you don't leave machines on 24/7 or have other devices connected to the internet and left switched on 24/7 -- e.g SKY Q boxes etc. Otherwise I'd use something reasonable like 30 days etc.
    One would have to know your setup and how often you disconnect devices. These days most things like TV's etc can be switched off properly without being left on standby - then on re-start DHCP will assign a new IP address.

    Any sensible router in its admin console will have a setting for DHCP lease time - should be easy to find - just logon to your router -- usually the address of the form 192.168.x.1 where x is often 0,1 or 2. If you have a really hot brand spanking new one the admin address might be in the IPV6 protocol -- look in the instructions and logon again to the admin mode.

    The user id is usually ADMIN and the password is password or pa55word unless you changed the default password.

    You should get some sort of GUI with the relevant options e.g

    DHCP lease time-screenshot_20210405_110815.png

    Cheers
    jimbo
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  4. Barman58's Avatar
    Posts : 3,930
    Windows 10 Pro x64 2004 - 19041 - 264 XP/Vista/Win7/Win8.1 in VM for testing
       #4

    All my devices have bespoke IP addresses in the assigned subnet and these are grouped by device type

    There is a DHCP server which is "hard coded" to reassign the specified IP address, should a device have a fit and lose it's assigned address.

    There are also a number of unassigned IP addresses in the DHCP Pool to assign "temporary" addresses to new devices or to visitors

    Visitors would normally connect to the guest network which gives password protected access to internet only, but there are a few addresses available should I allow someone to attach to the main network, [Technicians etc]

    Obviously, where practical, suitable fixed devices are connected via Gigabit Ethernet rather than WiFi for stability, Even though my WiFi has higher speed and bandwidth (Up to 3.2Gbps Tri Band WiFi 6 enabled for future use) I can sit in the car parked over 50 Metres from the flat and still get wifi.

    The setup is based on experience in my past roles in Network design and management the actual lease time in my setup only applies to the guest network, which as it is temporary by design, is set to 60 minutes to keep the pool available
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  5. Samuria's Avatar
    Posts : 6,054
    windows 10
       #5

    Having a short lease can be a problem if the router is busy it can be slow renewing so you can get drops
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  6. teots's Avatar
    Posts : 222
    Windows 10 64 Bit Home Version 20H2
    Thread Starter
       #6

    To syntoh, i have read that before posting, i want to know what's the best setting for me.

    To all, is it better to set the DHCP to max (2880 mins) for online gaming and downloading large files ?
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  7. Barman58's Avatar
    Posts : 3,930
    Windows 10 Pro x64 2004 - 19041 - 264 XP/Vista/Win7/Win8.1 in VM for testing
       #7

    If there is an active connection to the router then the lease time should be irrelevant.

    The lease only comes into effect when the device stops transferring data to or from the Router, once this occurs the Clock Starts and when the lease time is reached the allocated DHCP address for the device is returned to the pool for reuse.

    Basically if you have a long lease set then the likelihood of a particular device getting the same address every time is increased, if the lease time is short then this is less likely but you will have moore addresses in the available pool.

    DHCP leases are important in locations where many devices connect to the network through the router such as business premises, or coffee shops, they are less important in a home situation and so leaving at default is just as good as any other lease time.

    It should not affect gaming servers and other services outside of the home network as the IP address and lease for the home address is set by your ISP and they also set the DHCP lease, if you need to keep the same IP address seen on the net most ISPs will, for a charge, assign you a fixed Address

    The internal address lease on your local network, can effect the availability of fixed items :- Printers, NAS servers, to the network but this should only be an issue if you only use direct IP access to access these devices, Windows naming conventions will be automatically updated by the Router so should work without issue
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  8. pparks1's Avatar
    Posts : 1,695
    Windows 10 Pro
       #8

    teots said:
    To all, is it better to set the DHCP to max (2880 mins) for online gaming and downloading large files ?
    That won't matter at all. Let's say you set a lease duration to 48 hours (2880 minutes). Lets say you turn on your computer at 1pm on Monday and it never had an IP address before. So, it will send a broadcast message out on the subnet for a DHCP server. The DHCP server sees the request from the MAC address of the NIC, let's say 00-01-ba-d1-ae-94. So, it will look in the table to see if it has a currently lease for 00-01-ba-d1-ae-94 and because it does not, it will assign an IP address from the pool to 00-01-ba-d1-ae-94, let's say 192.168.1.100.

    So, now 192.168.1.100 is assigned to 00-01-ba-d1-ae-94 for a period of 48 hours. Since we we performed the above at 1pm in my example on Monday...that address is yours until 1pm on Wednesday.

    The way DHCP works is that once you hit the 50% lease point (24 hours in this example), your PC will attempt to renew 192.168.1.100 with the DHCP server. It will send a renew message, and the DHCP server will make sure that this IP hasn't been given to anybody else, and since it hasn't (it's been yours since Monday), it will renew 192.168.1.100 for 00-01-ba-d1-ae-94 for another 48 hours...and thus at 1pm on Tuesday, you will now have the IP until 1pm on Thursday.

    So, let's say at 2pm on Tuesday, you turn off your computer, just 1 hour after you got your lease extended. Now, you leave your computer off for 4 days. So, on Saturday at 4pm, you turn it back on. It will see that it previously had 192.168.1.100 and it will attempt to renew that address. It will ask the DHCP for that IP. The DHCP server will check to make sure that it hasn't given out 192.168.1.100 to anybody else and if it has not, it will give it back to you again and record a new 48 hour lease for 192.168.1.100 to 00-01-ba-d1-ae-94.

    As you can see, DHCP will try at multiple intervals to renew an IP address that you have. No matter what the lease duration, if your computer is on, or you don't have a ton of client devices, you will almost always keep the same IP address.
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  9. teots's Avatar
    Posts : 222
    Windows 10 64 Bit Home Version 20H2
    Thread Starter
       #9

    Thanks to both of you. Btw, what is the DHCP lease time setting for both of you ?
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  10. pparks1's Avatar
    Posts : 1,695
    Windows 10 Pro
       #10

    Mine is 24 hours, and I am using Google Wifi and I don't think is adjustable.
    DHCP lease time-image.png
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