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It's said in text book that, switches are unable to connect heterogeneous networks (networks with different link layer technology).
However, wireless access point do connects different networks (wireless and wired). Why people say it's a link layer device?
Thanks!
Technically most access points are a bridge. Bridges also operate at the Data-Link layer. A switch is simply a multiport bridge.
They are Data-link layer devices because they use the layer 2 (Data-link) addresses to determine where to forward frames (layer 2 data is called frame, layer 3 data is called packets). More specifically they use the data-link layer address (MAC address for Ethernet) to determine which port the frame should be forwarded.
Any device that operates at one layer also operate at all lower levels. Therefore they can convert from one layer 1 protocol (Ethernet) to another (Wireless).
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ARP and RARP are the main Protocol uses in Link Layer. To do the ARP request, a device requires IP and MAC address pair for broadcasting. So my question is ARP doing the mapping the IP to MAC by referring the data
and operates using the LAN.
So RARP is the reverse algorithm of that like mapping logical address to physical address in caches in Computer Systems.
I hope a good answer from the community.
There are dozens of protocols that use the data-link layer the same way ARP does, including IPv4, IPv6, etc. See IEEE 802 Numbers for a list of protocols that use the data-link layer.
For protocols in the data-link layer, there are/were many. For example, token ring, ARCNET, FDDI, frame relay, HDLC, ATM, PPP, etc. Ethernet used to be the king, but Wi-Fi has dethroned it since there are more devices shipping with Wi-Fi interfaces than devices with ethernet interfaces.
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I have mounted two ethernet adapter on my pc and each of them has connected to a seperate network. The problem is that only one of them is active at a same time. In other verb I can ping only through one of them at the same time and if l want to ping another network l should disable the first adapter. So now l want to know how can I use both of them same time.
Avoid assigning multiple adapters in the same computer to the same subnet.When configuring multiple NICs, each NIC should communicate with a different subnet. Configuring two or more NICs on the same subnet may cause communication problems. Delve deeper in this article. There're also example scenarios using two adapters
Also you just can assign 192.168.0.16 to the first adapter, and 192.168.1.16 to another
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HDLC/PPP protocol as described is layer 2 protocol.
But I have the confusion of why is this required to be configured on a routers serial interface.
that too when the connection is as below,
Router1----DTE-----SERIAL--------DCE--Router2
Adding more Info: What if this had only switches instead of routers
good fundamental question. HDLC / PPP are certainly layer 2 protocols. I will try to explain why layer two configuration is required on router interface.
What we actually mean when we say that router is layer 3 device?
When we say router is layer 3 device that means it can operate in layer 3 and all layers below it. [I will give you an analogy in real life, when we say the Building has 3 floors means it has floor 1, floor 2 and floor 3]. Same as router works in layer 3 means it operate at maximum on layer 3 but also performs layer 2 and layer 1 functions.
In detail –
When router has a packet to be sent out. It does following action.
A) Layer 3 function
i) Firth will check the network is present in routing table.
ii) If yes, it route the packet to outgoing interface.
Now outgoing interface is having the packet in its queue and need to put on physical channel.
B) Layer 2 function
i) Before sending it on physical channel, router now need to encapsulate the IP packet into a new layer 2 frame, depending on data link in between two router. A frame begins with (frame start) - preamble and delimiter frame. So IP packet can be carried out as a frame on transmission network. Router frames it into PPP or HDLC frame format. The encapsulation should be same on both the routers.
C) Layer 1 function
i) Once the frame is available in cache memory of the interface. Router interface converts it in BITS and transmits it on physical line.
Please feel free if you still have doubts.
Hope that helps
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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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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.