DHCP necessary on small home LAN with router?

[BlueWeasel]

I recently got a US Robotics 4-port router, and I'm trying to set it up as a simple 100mbps hub on my small home LAN (3 systems max).

I don't plan on sharing the Internet, so I'm not going to use the router features yet.

Currently, I've got a static IP LAN setup using the following IP addresses:

Router 192.168.0.1
Main System 192.168.0.2
Server 192.168.0.3
Laptop 192.168.0.4

I've plugged the new router/hub in, and have disabled DHCP in the router settings, but I can't ping any of the other system's IP addresses from my main system.

If go into the router and enable DHCP, and then go into the network settings of each system, and enable "Obtain IP Address Automatically", then everything works like a champ.

The reason I've disabled DHCP is I've heard it can possibly slow down the network because each system has to wait on an IP address. Since I'm only running a small 3 system LAN, I always figured that disabling DHCP and going with static IPs is the best way to go.

Is it possible to run with DHCP disabled, or should I even bother?

 

[JackMDS]

Originally posted by: BlueWeaselThe reason I've disabled DHCP is I've heard it can possibly slow down the network because each system has to wait on an IP address. Since I'm only running a small 3 system LAN, I always figured that disabling DHCP and going with static IPs is the best way to go.

I wonder which Yeti told you that? :shocked:

After the first time use the IP and the associate MAC number stay in the Router memory and as long as you do not exchange computers each computer will stay with the same IP.

The saving of time that the Yeti is talking about might be few milliseconds. when the system is booted.

I would suggest that unless you have another good reason to change you should leave it alone.

:sun:

 

[Goosemaster]

Yes you can run with DHCP enabled. You will never come to realize a performance gain.

Static IPs can be intermingled with DHCP as well. This comes into play when you have a server that REQUIRES a static IP etc or that you need to keep track of based on IP.

 

[OMG1Penguin]

If you are concerned about DHCP traffic, set the lease high on the router. Also, make sure the default gateway, dns server, and wins server addresses on the clients are set to the router, if you're using static IPs

If DHCP is enabled, and you are using static IPs, it won't create any traffic. DHCP is a listening service, it doesn't go out and mug clients to see if they have ip addresses or not.

And on a network that small, your bottleneck will be internet connection, DHCP won't have any bearing on throughput, even if you have small lease times.

 

[BlueWeasel]

Thanks for the info...it's extremely helpful.

I'm still a little confused though. Right now, I've setup up the router to give each machine a specific IP based on it's MAC address. The IP addresses are the same as I tried setting up as static initially (see OP).

Main System 192.168.0.2
Server 192.168.0.3
Laptop 192.168.0.4

I know though DHCP is still enabled, but I'm just assigning specific IP addresses to specific machines. Does that provide any advantage over letting DHCP assigning random addresses from an IP of say 192.168.0.2 through 192.168.0.10?

I honestly couldn't tell much of a difference in speed with DHCP enabled on the router, compared to when the main system and served were connected by a single crossover cable. 🙂

Eventually, I'll probably add my cable modem to the mix, so it appears the best bet is to stick with DHCP.

 

[OMG1Penguin]

Assigning ip addresses through the router still uses DHCP (client reservations).
Assigning the information to the machines (at the machines) will not use DHCP, but you have to put in EVERYTHING, or some services will not work.

There is a reason DHCP is used on large scale networks, the convenience (of administration) outweighs the utilization (almost nil with high leases) of the network.

The only traffic DHCP generates is when systems are powered on, and then at the halfway point of the lease you specify (clients renewing the lease). There is no constant strain on the network.

edit: and even when DHCP generates traffic, it's only a couple quick exchanges of information.

 

[BlueWeasel]

OMG1:

What exactly are you referring to regarding "leases"? I don't see any kind of option or setting like this in the router setup, but it may be listed as something else.

 

[Nothinman]

I'm still a little confused though. Right now, I've setup up the router to give each machine a specific IP based on it's MAC address. The IP addresses are the same as I tried setting up as static initially (see OP).

Which is pointless unless you need to forward ports to a certain machine or something, setting reservations just creates additional overhead on you because you have to change them if you get a new NIC or something.

I know though DHCP is still enabled, but I'm just assigning specific IP addresses to specific machines. Does that provide any advantage over letting DHCP assigning random addresses from an IP of say 192.168.0.2 through 192.168.0.10?

The only advantage is that you would know the IPs but if you have a decent infrastructure setup you don't need to know them, because you should be referring to the boxes by name anyway.

Eventually, I'll probably add my cable modem to the mix, so it appears the best bet is to stick with DHCP.

Yes because it means 1 place to make changes. If you want to change your IP scheme for whatever reason, just change the router and the boxes will all get the new information the next time they get a DHCP lease. Want to setup an internal DNS server? Just change the DNS IPs in the router, when the boxes get a new DHCP lease they get the new DNS server IPs too, etc.

A DHCP client leases an address from the DHCP server, when a client boots up it broadcasts "Hey, any DHCP servers here?" and the server says "Yup, you can have this IP for this long" and after that time is up the IP is up for grabs again. Most DHCP clients will renew their lease automatically so they're never stuck in limbo.

 

[skyking]

The way the DHCP system works, is like this:
When a computer starts up, it requests an address by asking over a certain port. The dhcp server is listening, grants that request, and "Leases" an address to the client. This lease length can be set in many but not all entry level routers.
Once the dhcp server leases the address to the client, the client computer sets it's address, gateway, and dns server according to information given by the dhcp server.
The entire transaction takes fractions of a second, and does not disturb any other network traffic at any appreciable level.
The transaction does not occur again for that computer until:
A) it is rebooted, or an ipconfig /renew is performed.
B) the lease is expiring and the client requests an address.
Unless you enjoy setting static addresses, or need to insure that a server or workstation remain at the same address, use dhcp.
Even when dhcp is enabled, the dhcp server will continue to give the same address out to the same network card, almost without exception.

 

[OMG1Penguin]

Lease is the length of time the DHCP server (the router) gives a client the IP adress for. Like a library book. The client will try to renew the lease half way through that time period.

I haven't seen another name for it, but the setting should from 2 hours - 8 days~ish.

 

[classy]

Originally posted by: OMG1Penguin
Lease is the length of time the DHCP server (the router) gives a client the IP adress for. Like a library book. The client will try to renew the lease half way through that time period.

I haven't seen another name for it, but the setting should from 2 hours - 8 days~ish.

Yes your correct. Skyking was off only on the reboot part. The lease is in effect for most routers at a default of 7-8 days. And it will not attempt to contact the dhcp server again until 50% of the lease is up.