Newbie--ip, static lease versus fixed IP address

[kdkrone]

I am re-doing my home network and have been searching out basic issues that I am having difficulty clarifying on the internet, so if anyone can answer or point me to where I can go on the internet, that would be appreciated.

First, WRT IP addresses. Am I correct that a private 192.168..... network, the xxx range is 1 - 254 or so? (about 255 addresses). Since many routers come with a default IP address of 192.168.1.1, is there any reason to change that? (years ago, the person who set up my network used .1.100 as the router address) Is it "safer" to use a different address for the router?

Next, WRT static leases, it had been suggested to me, and it worked, to assign static leases to some replaytv's that I had, as they were assigned their addresses more quickly on reboot of the router (if it was necessary). I no longer have them, but I remembered that and have used the STATIC LEASE screen on my DD-WRT console to give static leases to my equipment, including computers, sonos sound bridge, roku, and slingbox, particularly for the slingbox so that port forwarding works. The question I have is, with regard to equipment that can be assigned a fixed IP address like a computer (using Windows networking and IPv4), is there an advantage of leaving the computers to be assigned a static lease, or should I set a fixed IP address for each piece of equipment that can accept it? I don't mind taking the extra time, if there is a reason. I have had to do it for a couple of printers that I have so that I can use their consoles to do modifications to them.

Last, I am trying to understand the use of the range of addresses in DHCP that can be used and how it is best used (Network Address Server Settings DHCP). If, for example, I decide to use 192.168.1.100-149 as available for lease assignments, should I keep the static leases outside of that range, or are they kept IN that range? If outside, then I could use 192.168.1.1--99 and 192.168.1.150-254----is that correct? I am trying to prevent any conflicts of IP addresses.

Thanks.
Ken K

 

[htismaqe]

First, WRT IP addresses. Am I correct that a private 192.168..... network, the xxx range is 1 - 254 or so? (about 255 addresses). Since many routers come with a default IP address of 192.168.1.1, is there any reason to change that? (years ago, the person who set up my network used .1.100 as the router address) Is it "safer" to use a different address for the router?

Without getting into too much detail, there are private addresses reserved in the 192.168 space, the 172.16 space, and the 10.0 spaces. They were originally reserved to be used as classful netblocks but we haven't used classful routing for many, many years really. If you want to know specific addresses that can be used, you can consult RFC 1918.

There really isn't any other reason to change a router's default IP address or netmask other than personal preferences. I generally don't use 192.168 addresses but using something else isn't inherently more (or less) secure.

Next, WRT static leases, it had been suggested to me, and it worked, to assign static leases to some replaytv's that I had, as they were assigned their addresses more quickly on reboot of the router (if it was necessary).

It's highly unlikely that using DHCP reservations (or not using them, as the case may be) will have any effect at all on how quickly a host acquires an IP address after a router reboot or other interruption. The host still has to request an address and the router still has to assign one. Assigning one via a reservation takes the same amount of time as assigning one from the pool.

If you really want the host to come back up "immediately" you would assign a static IP address on the host and not use DHCP at all but that's really not a great option, IMO. DHCP works just fine and the difference is literally milliseconds anyway.

I no longer have them, but I remembered that and have used the STATIC LEASE screen on my DD-WRT console to give static leases to my equipment, including computers, sonos sound bridge, roku, and slingbox, particularly for the slingbox so that port forwarding works. The question I have is, with regard to equipment that can be assigned a fixed IP address like a computer (using Windows networking and IPv4), is there an advantage of leaving the computers to be assigned a static lease, or should I set a fixed IP address for each piece of equipment that can accept it? I don't mind taking the extra time, if there is a reason. I have had to do it for a couple of printers that I have so that I can use their consoles to do modifications to them.

I use DHCP reservations for every device on my network. I do that because I then know what device I'm looking at just by seeing the IP address. It makes troubleshooting easier, at least for me. That being said, the only hosts that really NEED reservations are those that need to accept connects from other hosts. So if you're using port forwarding, you'll want to use reservations. Printers should use DHCP reservations. If you have a host that you frequently access via remote desktop or something similar, or if you have a PC or NAS doing file sharing, use DHCP reservations. If the host in question, like say a smartphone, is not accepting connections and is only initiating connections, then it doesn't need a DHCP reservation.

Last, I am trying to understand the use of the range of addresses in DHCP that can be used and how it is best used (Network Address Server Settings DHCP). If, for example, I decide to use 192.168.1.100-149 as available for lease assignments, should I keep the static leases outside of that range, or are they kept IN that range? If outside, then I could use 192.168.1.1--99 and 192.168.1.150-254----is that correct? I am trying to prevent any conflicts of IP addresses.

Different brands of consumer routers work differently in this regard. Some firmware, like Netgear, require you to setup a DHCP pool and then setup your reservations OUTSIDE of that pool.

Linksys Smart Wifi firmware, like on the WRT1900AC, requires that the DHCP reservations exist INSIDE the DHCP scope.

What kind of router do you have specifically? As long as you're using DHCP for every device on your network, you won't have any IP address conflicts because you're giving your router 100% control over IP address assignments.

 

[azazel1024]

As above, but to add a bit.

For assigning a static IP address to the client and not using DHCP at all. About the only two reasons to do this are if the client does not support getting a DHCP reservation, or if you want the device to still interoperate with any other statically assigned devices on the network if the DHCP server goes down for some reason.

For assigning a reservation (or static), the big pro here is if you need to access to the gear on your network and the service you are using does not do network service name resolution (NetBIOS, LLDP, UPnP). Example, getting to the admin console of an access point connected to your network. Or accessing a server possibly.

For most stuff, it really doesn't matter if the IP address sometimes shuffles around a little. Occasional services just don't handle the IP address changing periodically (see above on the network service name resolution bit. I had a media streamer that you could enter the machine name or the IP, but if the IP changed later when you entered the machine name, it often broke until you rebooted the media streamer).

Me personally, I use the 192.168.1.x range, because it is what I use, so I remember it. I always leave my router on .1 and all of my network gear on .200 or greater. I assign a reservation to my server NICs, but that is it. The networking gear has static IPs so it never has to rely on DHCP from my router.

.253 and .254 are my access points and .250, .251 and .252 are my switches.

 

[kdkrone]

Thank you both for your replies. WRT your question, HTISMAQE, I presently have a Linksys 150n runnign DD-WRT firmware. It had been setup with a router of 192.168.0.100 and a DHCP range of 100-150. Almost all of my equipment has static leases, including computers (laptops and desktops), iPads, phones, Slingbox for port-forwarding, Sonos bridge, and a bridge to control window shades. (I had been using a Linksys 300n but am trying to recover from a bad firmware update....).

I see that the main reason for having had static leases was to assure that certain pieces of equipment that needed to have port forwarding, like my Slingbox.

I have decided to change to a more powerful router, so I purchased an Asus RT-N68U, which arrived Weds. Looking at its software, I think I will keep the native ASUS software and thought I would pretty much keep the same IP ranges with some minor modifications. I wanted to "organize" my IP addresses so that I could recognize any outside intrusion, as well as to make any troubleshooting easier, hence the questions here.

(different topic: do either of you know whether, if I set the new ASUS router as my main router, whether I can use the Linksys with DD-WRT firmware as an access point? I have one spot where I may need one. I will check elsewhere in the forum if you do not. Thanks)

 

[htismaqe]

I wanted to "organize" my IP addresses so that I could recognize any outside intrusion, as well as to make any troubleshooting easier, hence the questions here.

That's exactly what I do. I even reserve some address space for future use using bogus entries so that truly dynamic devices are forced to receive addresses from a certain part of my pool.

 

[kdkrone]

Great minds... (by luck on my part). The other day after I bricked my 300n and pulled my 150n into service, I had experimented with your process by putting in addresses with MAC addresses of 00:00:00:00:00:01, etc., and that seemed to work.

By the way, other than using an ipcofig /release, then /renew command, is there any way from the router side to speed up DHCP assignments?

 

[azazel1024]

Great minds... (by luck on my part). The other day after I bricked my 300n and pulled my 150n into service, I had experimented with your process by putting in addresses with MAC addresses of 00:00:00:00:00:01, etc., and that seemed to work.

By the way, other than using an ipcofig /release, then /renew command, is there any way from the router side to speed up DHCP assignments?

Yes, change the lease time. Or do you mean how quickly an address is actually assigned? For the later, no. It is dependent wholey on the router AND client. On the order of miliseconds (probably tens of miliseconds). In terms of how often it requests one, that is up to the DHCP server/router. Generally you can set lease times from a few minutes up to around 2 days is they typical I see (generally from 1-2880 minutes). I set mine to 12hrs. You usually only need to set it low if you have a lot of clients joining and leaving your network so that you can keep the DHCP table smallish/keep from exceeding the pool size.