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whats the purpose of local IP addresses if there are mac addresses? ARP maps mac addresses to IP addresses but I don't see why it's needed, because I thought data on LANs are sent as frames which only care about the mac addresses.
Long ago and far away, there was more to the world than Ethernet LANs, and application writers didn't care whether your PC was attached to an Ethernet, a Token Ring, an XNS net, or dial-up. IP provides a layer of abstraction and coherence across the top of all those and many more, allowing application authors to ignore the differences between them.
And what happens if you want to talk to a macine that isn't on your local area network (such as StackOverflow).
IP allows routing of packets anywhere, not just locally in your current network segment and, though it's mostly over Ethernet now, IP can equally well work over other underlying layers, giving a consistent view to the upper layers. This is vital given how much stuff is actually built on IP (DNS, FTP, SSH, HTTP and so on).
Machines almost certainly will cache IP-to-ethernet details to speed up subsequent transfers so the impact of translation on the LAN isn't so bad.
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I have a HP ProCurve switch, I recently added 2 new machines to the network, which I had to assign the IP addresses to manually. Now using these 2 machines I can ping my current machine and other machines on the network, however if I try to ping those 2 machines from my current machine (or others on the network) it does not go through. So my thoughts are that the router table has not updated so that's why I can't ping them from machines that have been on this router.
(Not too sure, not enough knowledge yet)
At least I think so. My question is does the Router Table update it's information automatically?
Assuming your HP Procurve is acting only as a switch, then the Routing Table should not be your problem. A switch does not route IPs, a switch is concerned with routing packets via their layer-2 addresses (MAC addresses). The switch determined which physical port is connected to a device with a MAC address, and when it gets a packet addressed to that MAC address, it sends the packet out that port. The mapping on port to destination mac address is stored in a CAM table inside the switch. This is very different from a routing table that maps IP address ranges to physical interfaces.
What is probably happening is that ARP is not resolving. ARP binds layer 3 IPs to layer 2 MACs in a local network. This can be cause for a few reasons. The first thing i would look into is if the switch has VLANs enabled. This makes the switch act like multiple isolated switches. After that you may need to look at your computers ARP tables to make sure they are correct. The arping command will be useful.
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Here is the scenery. I have several buildings with same subnet IP addresses (192.168.0.0/24).
I need to secure that connection with OpenVPN.
Please assist me how can I organize VPN connection with IP network 10.10.10.0/24
example
HQ (192.168.0.0/24) - VPN 1 (10.10.10.50) --- VPN 2 (10.10.10.51) - Branch (192.168.0.0/24)
I meas assist with NAT if it will be needed or if I just connect , the C class traffic will just be passed through.
Thank you
Since you are merging two nets, you should use TAP interfaces.
TAP (as in network tap) simulates a link layer device and it operates with layer 2 packets such as Ethernet frames. TUN (as in network TUNnel) simulates a network layer device and it operates with layer 3 packets such as IP packets. TAP is used to create a network bridge, while TUN is used with routing.
This way, you will be joining the HQ network with the branch network like if you plug a (secure, pre-shared key may be ok) ethernet cable between them.
But this will likely crash both environments if they are operating now without knowing one about each other. Maybe the HQ router has the same IP as the branch one, or maybe not, but they are both acting as DHCP servers and now they will be on the same network.
Do you really need to merge both nets? I think you should consider to do some network design and let the HQ on the 192.168.0.0/24 but change the n-th branch to 192.168.n.0/24. Then you can do a TUN OpenVPN setup and route between branches and HQ in a hierachical way. It will save you some bandwith too by not spreading irrelevant broadcast traffic over the tunnel.
Thank you
Well you know, I do not have any router installed in HQ side or anywhere in network and maybe that is a big minus (and I will fix that in a time). Now I just need to secure the links between HQ and branches so the optical network provider (that provides links) could not access out data. If you have any good solution please write.
Thank you
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Suppose we have messenger like GTalk, Skype etc running on two different PCs(A and B) which have private IP addresses but connected to Internet through some ISP. The two PCs could be located in different parts of the world. Now its possible to send messages and make VoIP calls between A and B.
This obviously uses server for communication establishment. For text messages it could be routed through the server to reach A and B.
But for VoIP calls, I believe initial establishment would be taking help of server and later VoIP data would flow directly between A and B. Now, A and B both have private IP addresses.
So my question is how is it possible to communicate between A and B directly over the Internet who have private IP addresses ?
Is there any specific standard for this ? I am not talking about VoIP standard like RTP etc but the mechanism to communicate over Internet using private IP addresses. In other words, I simply have a TCP client and TCP server running on A and B respectively. How can TCP client reach TCP server ?
I would like to know if messengers like GTalk, Yahoo, Skype and many of the Android applications like Viber, Kakoa talk, WhatsApp etc use any specific standard for this. And I have seen that these work almost always, calls between A and B work, located anywhere in the world.
It would be nice if somebody can share the architecture and the concepts involved.
[I did read about concepts like STUN and hole punching. But I don't see any specific way. And there is no guarantee that these would work depending on the NAT behavior]
Thank you.
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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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MAC address are used for uniquely identifying my computer.
IP address are used for routing the packets to the network, as it has got a hierarchial structure, but it doesn't uniquely identifies a computer. So, after IPv6, each computer will have a unique IP address, so will there be any need of MAC address then?
Please do correct me, if I had understood something wrong.
No. MAC addresses operate at layer 2 ("data link layer"). The Internet Protocol (both IPv4 and IPv6) operates at layer 3 ("network layer").
These two layers are complimentary, and do not "replace" each other. For more information, read up on the TCP/IP suite.
IPv6 stateless address autoconfiguration (SLAAC) uses the MAC address to generate the address, but that does not mean they "replace" each other. It's simply a characteristic of the layer 2 interface being inherited by the layer 3 addressing. Other than that, completely complimentary.