Adding a wireless access point - why assign IP outside DHCP range?

[kamaran]

Sorry if this is a silly question..

As per the title, when adding a wireless access point, why is the recommendation to assign it an IP address outside of the DHCP range. Why not just assign an IP within the DHCP range and reserve it for the access point within the router settings?

Thanks

 

[ubimea]

I think this is a good question; in fact I do the same thing.

I reserve a static ip address on the main router for the mac addresses of the access point, and it has been rock solid for a long time.

I suppose not every router permits assignment or is easy to configure with the reservation, hence the advice.

Also, I have in the past organized clients by groups; for example, dhcp addresses to be handed out are at xxx.xxx.xxx. 2-50; access points start at xxx.xxx.xxx.100; wireless printers and print servers at xxx.xxx.xxx.150 and so on.

 

[overdrive31]

Putting the static IP in the DHCP reservation is the exception to the rule(usually is required when port forwarding to such is needed as well), otherwise if the lease runs out while the static IP device is not online, and it's IP gets reassigned to another device, it will not be able to function until it's IP gets released. Thus, do not put non-DHCP reserve static IP devices in the DHCP pool. It's like beer and wine, they don't mix well after a while.

 

[stevech]

Sorry if this is a silly question..

As per the title, when adding a wireless access point, why is the recommendation to assign it an IP address outside of the DHCP range. Why not just assign an IP within the DHCP range and reserve it for the access point within the router settings?

Thanks

short: Using DHCP for the access point - means you won't easily know its administrative IP address in the future.

 

[kamaran]

short: Using DHCP for the access point - means you won't easily know its administrative IP address in the future.

Thanks for the post, as the post says, it's within DHCP range but a static reserved IP

 

[kamaran]

Putting the static IP in the DHCP reservation is the exception to the rule(usually is required when port forwarding to such is needed as well), otherwise if the lease runs out while the static IP device is not online, and it's IP gets reassigned to another device, it will not be able to function until it's IP gets released. Thus, do not put non-DHCP reserve static IP devices in the DHCP pool. It's like beer and wine, they don't mix well after a while.

If its IP is reserved, surely no other device can be assigned its IP?

 

[overdrive31]

If its IP is reserved, surely no other device can be assigned its IP?

True. That is the exception, as you do have to assign an AP it's static IP, and if you do not add that IP to the DHCP reserve. Then if the static IP exists in the DHCP pool, you will have problems.

The problem being if you put an static IP that is not DHCP reserved, but in the DHCP pool, it's IP can potentially be given to another device causing problems.

As long as you assign the AP a static IP outside the DHCP pool or in the DHCP reserve, you should have no problems.

 

[keenanj]

The only time you would use a DHCP reservation is for a device in DHCP mode that you do not want to configure with a static. Something that is hard to configure like a set top box or game console but does not need to be managed.

You always want to set the access point static IP for 2 reasons.

you will know the managment IP address.

If the AP comes up and can not contact the DHCP server you can still manage it.

 

[ubimea]

Sorry if this is a silly question..

As per the title, when adding a wireless access point, why is the recommendation to assign it an IP address outside of the DHCP range. Why not just assign an IP within the DHCP range and reserve it for the access point within the router settings?

Thanks

Back in the day, (and maybe not all modern routers) ip addresses could not be reserved by device mac address, so it was required to set your static leases outside of your automatic DHCP address range.

It is no longer NECESSARY to set your static leases outside of your automatic DHCP address range, but you still see that it is frequently recommended.

 

[sfx2000]

Sorry if this is a silly question..

As per the title, when adding a wireless access point, why is the recommendation to assign it an IP address outside of the DHCP range. Why not just assign an IP within the DHCP range and reserve it for the access point within the router settings?

Thanks

Management - not all DHCP servers reserve an address per MAC - having a static IP allow you to got to XXX.YYY.ZZZ.WWW to configure and adjust the wireless settings of that AP.

 

[overdrive31]

An router turned access point really is just a bridge, you do not technically need it's static address to exist in the same subnet, this will avoid any DHCP issues, it just makes managing settings somewhat more difficult by needing to switch a client to the AP's subnet just to change settings, then switch back.

 

[YeOldeStonecat]

Sorry if this is a silly question..

As per the title, when adding a wireless access point, why is the recommendation to assign it an IP address outside of the DHCP range. Why not just assign an IP within the DHCP range and reserve it for the access point within the router settings?

Thanks

If you reserve in (or put it in an exclusion range) in the DHCP services..that' fine. But generally it's suggested to give any static IPs outside of the DHCP lease pool...because if you assign a local static IP that is in the DHCP lease pool, the DHCP service will not know about it and it may give that IP out to a device that asks for one...and suddenly you have a nice DHCP conflict causing issues.

Example....
Router at 192.168.1.1
Usually IP leases are given out starting at .100. So the first device to boot up gets 192.168.1.100, next device 192.168.1.101, etc etc.

You have .2-.99...for your static assignments...like servers (I like to do my servers starting at .10), printers (I start printers at .20).

Say you manually set a printer, or server, or access point..at 192.168.1.110. Say you have at least 10x other dynamic device on your network...one of them will boot up, ask for an IP from DHCP..the DHCP may lease out .110...because it doesn't know it's taken..and WHAM...problems!.

Now, some DHCP services have an "exclusion range"...into which you enter IP addresses they are never to use, because you've programmed some devices locally with those IPs. (servers are commonly locally assigned IPs...not through reservations). Usually important devices that have to be available on the network at higher priorities are locally programmed with their static IP address. Less to go wrong.

If you use your DHCP service for "Reservations"...where you tell it what IP address to give certain devices...it already knows about that IP, so all is good.

Access points are commonly in the .240 - .250 range...it's just common to have that. A lot of us prefer to follow the usual best practices, commonly used approaches, so that other techs that work on our stuff can more easily..work on the network.