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How can we determine if an IPv6 address is within a private CIDR?
On IPv4 it's straightforward, the subnet and the DNS mask are simple enough to understand.
With IPv6 every resource I find looks like the table below - but my own local IPv6 address starts with fe80, which doesn't seem to conform to the fd00 pattern indicated.
Can anyone help me understand private IPv6 ranges and why my own private IPv6 address would seem not to be in that range?
IPv6 does not have Private addresses the way IPv4 does. IPv6 used to have Site-Local addresses that were analogous to IPv4 Private addresses, but those were deprecated in favor of ULA (Unique Local Addressing), fc00::/7, of which the second half of the addressing, fd00::/8 is available for local assignment, but requires the next 40 bits to be randomly chosen. IPv4 Private addresses and the (deprecated) IPv6 Site-Local addressing were expected to have the same addresses used in multiple sites, but IPv6 ULA is expected to be unique with little chance for duplicate addresses.
What you are looking at is a Link-Local address (in the fe80::/10 range). Packets using Link-Local addresses are confined to a single link, unlike IPv6 Global and ULA addresses. You cannot route packets with Link-Local addresses as all links use the same Link-Local network. You can route ULA addresses, but not on the public Internet. Global addresses are globally routable.
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A company is granted a static address 192.168.10.0.
The Company wants to have four subnets for four of its departments. Each Department is having 50-60 computers.
Design Subnetwork using sub netting concepts.
Identify Number of IP addresses on required in each Subnetwork.
Write their starting and ending addresses.
I am not getting, how to approach this problem.
Thanks in Advance
The company is granted a static address of 192.168.10.0. The company wants to have four subnets for four of its departments. Each department is having 50-60 computers.
To design the subnetwork, we will use the subnetting concepts. The company has been granted a static address of 192.168.10.0. This is a Class C IP address. The first octet (192) is the network address and the last three octets (168.10.0) are the host addresses.
To create four subnets, we will need to borrow two bits from the host addresses. This will give us four subnets, each with 62 host addresses. The first subnet will have the network address of 192.168.10.0 and the last subnet will have the network address of 192.168.10.192.
The first subnet will have the starting address of 192.168.10.1 and the ending address of 192.168.10.62.
The second subnet will have the starting address of 192.168.10.65 and the ending address of 192.168.10.126.
The third subnet will have the starting address of 192.168.10.129 and the ending address of 192.168.10.190.
The fourth subnet will have the starting address of 192.168.10.193 and the ending address of 192.168.10.254.
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So, i was reading networking in depth. One concept i failed to understand was how different machines in LAN manage to access internet through one public IP address provided to company by ISP.
For eg. let's say the public address provided is 244.13.5.89. And all the machines when get to internet, they all are recognized as 244.13.5.89 despite their private address being 192.168.3.x, which is fine. But now when the router sends the request for each of these machines, how does it maps each response to respective machine?
If the answer is NAT, what entries does NAT has? Is there port no. or something else?
I will give you the idea about the complex case scenario :-
If all datagrams arriving at the NAT router from the WAN have the same
desti- nation IP address (specifically, that of the WAN-side interface
of the NAT router), then how does the router know the internal host to
which it should forward a given datagram?
The trick is to use a NAT translation table at the NAT router, and to
include port numbers as well as IP addresses in the table entries.
See more details about NAT Table here.
SORRY, don't know why it took me minutes to post an answer, it was not allowing me to add the answer...
NAT has following fields:
source computer address and website, so when it receives packet it will replace source computer address with its public address, and send it to the internet once response comes back it sees oh this come from the website and it was requested by the source computer. It will again replace destination address with source computer address and send it in LAN.
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I'm trying to understand NAT (Network Address Translation) .
Can someone explain how can I determine if my computer is using a NAT (behind a NAT) , or
if it using its own IP address ?
What Barmar said in the comments is the easiest way. Obtaining your IP address over HTTP is indicative that you are behind either a NAT or an HTTP Proxy server. (I suppose it's possible you could have a public IP address, but your device is configured to route HTTP over a caching proxy).
Formal NAT detection and NAT classification can be done with the STUN protocol or equivalent protocol in which a UDP or TCP service echoes back the IP address back to the client that connected to it.
Another telling sign if you are behind a NAT is that your local IP address is in a private IP address range such as the 192.168.x.y range, the 10.x.y.z range, or then 172.16.0.0-172.31.255.255 range.
And pretty much any Wi-Fi setup is going to be a NAT configuration.
The NAT detection technique is based on two observations about the IP TTL (Time To Live) field.
Host operating systems have characteristic initial TTL values. This property of individual operating system implementations of TCP/IP is well known and can be used as part of a "fingerprint" to identify the operating system that a host is running merely by examining its traffic.
NAT devices or gateways decrement the TTL on packets that they forward.
For more details visit: http://www.sflow.org/detectNAT/
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I understand that a router uses NAT to translate the public IP we get from the ISP to say 300 local IPs. Does a switch perform the same function? If not, how's it different?
No, a switch cannot perform NAT and translate public(s) IP addresses into private addresses.
A switch is a network device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2). So, they are not aware of IP addresses which are network layer (layer 3). A switch keeps a record of the MAC addresses of all the devices connected to it. With this information, a switch can identify which system is sitting on which port. So when a frame is received, it knows exactly which port to send it to, without significantly increasing network response times.
Routers are network devices used to interconnect two different networks (with different IP addressing schemes).
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How many ways can 1 IPv4 address be interpreted, considering subnet masks? According to wikipedia, it seems like there are 32 possible subnet masks to 1 IP address, but I don't know.
It's not clear to me if a "network mask" is the same as a "subnet mask"; is there such a thing as applying more than 1 mask to an IP address?
network mask and subnet mask are essentially the same thing although there may be different representations. 255.255.255.0 or /24 are both mask representations. A give IP address can fall under different net masks, but there are some standard guidelines. Class A networks are generally lower numbers in the first octet. 10.0.0.0 is a Class A private space with a mask of 255.0.0.0 What that means is 10.anything is part of that network and should not be routed outside that network. you can do things like superneting which means change the subnet to something like 255.252.0.0 which limits the addresses in the network but is not a class a b or c. class B network is 255.255.0.0 . Class C is 255.255.255.0 . Class C is more commonly seen in home environments with a private address space of 192.168.x.0-255. as far as interpreting an ip address, any address is 1 address. the subnet mask tells you if it is a broadcast address(highest address) or a prefix(lowest address) or a valid address in the address space. it also tells a router if it should route the packet or not.