CurtPalme.com Home Theater Forum

[stefuel]

May be off topic but is HT related anyway
I'm trying to add another device to my LAN. It's a Escient server to control a Sony disc changer. It's trying to connect using the same IP address as something else on my network. How does DHCP using temp IP address allocation work?
Does everything on the network have to be connected and turned on and then re-boot the router for this to work?
I was trying to do this last night but did not want to disturb the kids sleep by going in and turning on their PC's.
Thanks,

[km987654]

If the other devices are PCs then perhaps a solution would be to release the IPs on the PCs or even just the one that is conflicting.

[MikeEby]

Most devices allow you to hard code a static address in them. That way you can be sure it's always where it should be. Also most router only allocate a range in the subnet to DHCP. The one I have uses 192.168.1.50 - 192.168.1.100 by default so just set the ip address on your server to an address that's free and outside of that range.

The router should also have a table that display all the devices that have ip address that were allocated by the DHCP in the router.

There should be no reason to reboot any devices on the network unless you change the subnet. Rebooting the router may not clear all addresss even with the computers shut off. If that's the case then you must do what KM suggests. Is the problem the Server has the same address as another device on the network?


Mike

[stefuel]

I will have to wait until tomorrow night to look at this again as I'm doing a double today and a regular shift tomorrow. I think the Escient is trying to use the same IP as my Sony BD changer. I'm trying to get this Escient and DVP-CX777ES to play nice so that I can take the std def DVD's out of the BD changer and free up space for BD's only.
The Escient and the 777ES are communicating fine via RS232, it's just this conflict in IP address that's screwing things up.

[TheVerge]

DHCP by design won't give 2 things the same address. Sounds one of the two devices has a static IP address.

[zaphod]

DHCP works works to give out IP addresses and supporting information (thatis, router/gateway, DNS servers, domain name and so on).

every network device built has a unique physical hexadecimal address of the form XX:XX:XX:XX:XX:XX where "X" is a digit from 0 to F called an ethernet or MAC address.

When a network interface is started up, the IP address that it uses is going to be either defined explicitly (called a static definition) or is retrieved from a server via one of any number of mechanisms, DHCP being one of them.

essentially it works like this.

the machine (client) puts out a broadcast message saying "hey - my MAC is XX:XX:XX:XX:XX:XX, does anyone have an IP for me?".
the DHCP server responds with "This is your IP"
the client returns "cool, i'll take it", and uses it

there is a lot more handshaking, but that's the crux.

The IP addresses given out by the server are defined in the configuration as either static or dynamic. static means that the DHCP server will give out the same address every time to the same MAC address. This is how i have the computers on my home network defined. Static addresses served by DHCP.

But if someone comes by with a computer, I don't know their MAC, don't want to bother getting it and putting it into the DHCP config, so i have defined a range of 10 or so dynamic addresses. This means that when the DHCP server sees a request from a MAC address for which it does not have a static address defined, it hands out one from the dynamic range.

Each and every IP address given by a DHCP server comes with a lease. when the lease expires on the client, it asks for a new address. in most cases it gets the same IP address again. When the lease expires on the server it is marked available and will be handed out at the next request for a dynamic IP.

Since the client and server leases timeout at the same time, the same address is usually given to the client. But if the client is turned off, and the server expires the lease, the IP could very well go to another machine requesting a dynamic IP number. In the case of static DHCP addresses, the same IP is always returned with the lease expires - that is why they are static.


Leases stop the DHCP from getting the same IP address. If you have two devices with the same IP address then you have a wonked out DHCP configuration - or one device is not listening to the DHCP server. while it may have an entry in the DHCP configuration, there is a good chance that the machine (client) is not configured to get it's IP from DHCP.

another, more complex possibility is that there are two DHCP servers on your network, and they are colliding in the addresses they give out (i've seen that before).

[km987654]

[stefuel]

[km987654]

[stefuel]

I think I may have found one problem. I started with a Fios 4 port router. I quickly ran out of ports so I bought a
Netgear 8 port gigabit switch. Right now I'm using 8 or 9 of the 12 available ports. I was just logged into my router and I found under system settings "Configure the number of concurrent users that can be logged into the router. That is set to 5. If I have 12 ports available shouldn't I set that to 12 or more as I also have wireless devices like Wii.

[TheVerge]

I don't know how those FIOS jobbies work, but with a regular router, there should be no changes necessary for dhcp.


If you are really bored, install Wireshark on a computer and turn both of those devices on, you can see the dhcp traffic in real time and diagnose the problem. I suspect one of them will not be asking for an IP address though.

[ChrisWiggles]

[stefuel]

I was busy and just ignored it for a couple of days and it seems to have sorted it's self out.