Let's say the DHCP SCOPE IS 192.168.1.2 - 192.168.1.255. The DHCP server will normally assign IP addresses dynamically in a sequenced order. What is the next IP in the sequence has been assigned to a node statically. Is the DHCP going to recognize that the IP is in use although it was not assigned by the DHCP server itself? Or is it going to assign the IP regardless and in that case it would cause an IP conflict?
Logically I would say it won't assign the statically in use IP but I'm asking this question because I never read something about it. Please include references if possible.
Thank You!
You can have IP conflits in you network if you assign direct in an computer in your network and the router (for example) decides to give the same IP to another machine.
What I usually do to have fixed ips in my server is put an IP reserv in my router, binding with the server MAC Addres.
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I recently got to know about DHCP that it dynamically assigns ip addresses to a computer. But what if two DHCP servers across the world assign a same ip address to two different computers. Doesn't it conflicts with the uniqueness property of ip addresses.
For example two DHCP servers assign ip address x to computer1 and computer2 and i wanted to send a mail to computer1 by looking at DNS server it should be send to ip address x. But there is a conflict as two different computers have same ip address x. could someone please clear my doubt.
Let say I want to contact a server whose domain name is example.Com and ip address stored in DNS server is 127.18.1.1 and DHCP changes the ip address for this server to some random value 127.19.1.1 then how is the address resolved since I'm contacting to example.com which has 127.18.1.1
There are a number of ways that this problem is avoided.
Firstly, by keeping networks small, segregating machines into specific functions, geographic areas, etc you reduce the risk of having a large pool of addresses in use.
Secondly, if you must have multiple DHCP servers on a network, then the address space should be split between them. So if you have 192.168.0.0/24, one server would handle 192.168.0.0/25 and another would handle 192.168.127.0/25
Thirdly, most DHCP servers will ping the IP address that they are going to offer before offering it. If the address gets a response it will be marked as Conflicted and won't be offered again.
What's the difference between these 2 local ip addresses? In terms of pro's , con's and usage?
Those a simply two separate IPv4 addresses.
The 172.0.0.1 address is a public address which should not be used unless you have been assigned the address block containing it by an RIR or your ISP (which was assigned the address block containing it).
The 192.168.0.1 address is a private address which anyone may use in a private network. This address cannot be routed on the public Internet.
I suppose you are talking about 172.16.0.0 because it makes no sense to compare 172.0.0.0 with 192.168.0.0 because 172.0.0.0 is a public IP address.
If you are talking about 172.16.0.0 instead of 172.0.0.0, then... both are private IP address. They are defined in the RFC1918
There is a good overview at the Wikipedia page but the main difference is the size of the segment.
The address 172.0.0.1 is not a local address, it is a web address.
If you instead meant 127.0.0.1 this is what is refereed to as the "Loop back" IP, and is often referred to as localhost. Connections to this IP target the computer of origin, and are intercepted by the network card in your computer and fed back into the same computer.
192.168.0.1 is an IP on your local network, this may or may not be your computer. This address is assigned by your DHCP server on your local network (usualy running on the router) and is subject to change unless you have configured your DHCP server to make it static
Which to use?
172.0.0.1 Use when you are trying to connect to a website/remote computer at that IP (most likely not you)
192.168.0.1 Use when you are trying to connect a computer/device on your local network that you know will be at 192.168.0.1
127.0.0.1 or localhost Use when you are trying to connect to a port on the same computer you are already on
I understand TCP/IP addresses, and I understand ports, but I don't know whether the ports are tied to the Host (and hence one host gets one port 80), or whether the ports are tied to the IP Address (and hence one host with 2 NICs/IP-Addresses gets 2 port 80s)?
A port belongs to an IP address. If a host has two NICs , and a program binds to only one IP address, the same port can still be used by another program(given that it binds to another IP address).
The answer is 'both'.
If you bind to a specific IP:port, you can have as many bindings using the same port number as you have IP addresses.
If you bind to 0.0.0.0:port, or ::port in IPv6, the port is global to all possible IP addresses of the host, including those that don't exist yet.
But I agree with #DavidShwartz, the question is a bit ill-formed. The fact is that the endpoint is defined by IP:port, not just by port. A port isn't a real thing that you can actually count. It's just a 16-bit number.
Is it possible to have one of our networked PC's to keep using the same IP address (192.168.1.54) so that if the master computer or a failure / shutdown etc happens then the system IP addresses are not reset so i don't have to update all the other pc's hosts files to this PC's new IP address?
You will need to make a reservation based on the MAC address of your network card. You can find this by typing "ipconfig /all" inside the command prompt.
The IP addresses can be reserved on your router or on your server depending on how they are distributed.
You should solve this in the DHCP server (typically in your router), make a reserved IP for the mac-address of the PC in question. Or you configure the PC to not use DHCP but configure a fixed IP. But that should be, if possible, an IP that is not in the DHCP range.
can one location have more than 1 IP address? I have 2 IP addresses and need to know if they originate from the same source. Thanks
You're missing clear definitions of "location" and "source" in your question but lets go with the assumption that you mean "physical machine" for both (as it's obvious that multiple machines will have different addresses and that a single machine can change its IP address over time).
In that case, the answer is yes. The operating system may bind as many IP addresses to a physical network port (and a single MAC -- the physical addressing used by Ethernet) as it wishes.
Binding multiple IP addresses was the standard way of doing "virtual web hosting" before HTTP/1.1 arrived with the "Host" header. The provider would use DNS to map different host names to different IPs on the same network (usually the same subnet as well) and then assign all of them to the same interface. The webserver would get address information from an incoming connection and based on the local IP address would know which virtual host was being accessed.
This led to a higher-than-typical use of public IP addresses but the practice is now gone with the proliferation of HTTP/1.1.
I'm not sure how Windows presents it, but Linux will present a physical interface with multiple IP addresses as multiple logical interfaces such as "eth0", "eth0:1", "eth0:2", etc. Each logical interface has a unique IP address even though they share the same physical interface.
This is hard to tell. Especially it is hard to tell if these IP addresses are from different times. Today I may have a different IP address than tomorrow.
Even they are from the same time, a load balancer im my internal equipment might send my packets over the fail-over line if the 1st one is overloaded or broken down.
One network adapter normally has only one IP address at once and a typical end user only has one network connection active, but even then the IP address can change. The user could switch from wireless to wired and back or a power outage might reset the ISP's DHCP server (assigning everyone a new IP address).
If you want to identify the user even if his IP address changes, you need to identify the user by his session id, stored in cookies. As two users can have the same IP address (a whole company could be behind a NAT), you should never rely on IP addresses for identification.