Comments by "Javier Flores" (@JJFlores197) on "What is a ROUTER? // FREE CCNA // EP 2" video.

  1. Each interface on a router and switch has its own MAC address. So when PC-1 sends a packet out to the internet, the packet first arrives at the router. At the L2 header, the source MAC is PC-1's MAC address and the destination MAC is the router's LAN interface MAC address. The router then sends this packet to its WAN interface where it changes the source MAC from PC-1 to its (the router's) LAN interface and the destination MAC to the router's WAN interface's MAC address.
    3
  2. There's a channel called TotalSeminars with a video: Mike Meyers on: Touring the Network Server Room that should give you a general idea of large networks and how they are physically setup.
    2
  3. Just keep in mind his video series is not complete. There's still a ton of information he hasn't covered which is important to know if you're going for the CCNA. He's a good presenter, but he still needs a lot of work to get his series finished.
    2
  4. As far as I'm aware, none of those services are peer to peer. That means that when you use FB Messenger to send a message to your friend who is on the same wifi network as you, the data goes from your phone to Facebook and then from FB to your friend's phone. The devices don't directly communicate with each other on the same network.
    2
  5. Switches operate at layer 2 of the OSI model. There are layer 3 switches which can operate with IP addresses but they aren't commonly used. At least I'm not aware of them being used that much.
    2
  6. Routers have MAC addresses on their interfaces.
    2
  7. Usually we refer to networks as a collection of clients. For instance, your home network is a network. All of the devices in that network can talk to each other. But if you want to connect to another network, like the internet for instance, you need a router and modem between your home network and the internet (technically your internet provider's network). There are DHCP servers whose job is to provide IP address and other network info to devices that connect to a network. So when you connect your phone to your home wifi, the DHCP server in your network (usually the router) will give your phone a private (local) IP address. Without an IP address, devices can't talk to each other. Now, in order to connect to the internet, you need a public facing IP address. The local IP address that your phone gets from the router is not routable and can only be used within that network. Your internet provider also has a DHCP server which assigns your router a public IP address from their pool of public addresses. Its the same overall concept as when your phone gets an IP from your router, but the servers at the ISP level are usually significantly more complex and configured to handle a very large number of requests compared to your typical home router.
    2
  8. You can still communicate with other devices on the network via IP addresses. The network switch doesn't understand IP addresses, but it will still forward the frame to the intended destination. This works because the computers and devices all work through the OSI model. Now, without a router, you obviously won't be able to talk to other networks.
    2
  9. CLI stands for command line interface. Its a way to type in commands to a computer or other device. On Windows PCs, you can open Command Prompt. Linux/macOS systems use Terminal. Cisco routers and switches are primarily configured through a CLI where you have to enter commands and parameters.
    2
  10. Routers have sophisticated routing protocols that allow it to find the next best hop to the destination.
    2
  11. The best improvement you can make is to buy a wifi access point and install it in an area where you don't have good wifi coverage. You will need to run an ethernet cable from your router to that area and connect the AP. If you want to tinker around with stuff, you can setup a DHCP and DNS server and take that off of your router, but you will need to have a decent understanding of those network concepts to set this up correctly. For most home use cases, there's no real reason to do this, that is unless you plan on tinkering and learning about networking.
    2
  12. I'm not sure what you're confused about... Cell phone networks also use routers and switches, but they work a bit differently than your typical home network. Mobile data works because there are cell towers that your phone connects to.
    2
  13. The switch only "acts" as a hub when a broadcast frame is received. By definition, a broadcast frame is sent to all devices on the switch.
    2
  14. Yes. Those routers shown are very different than your typical home router. Cisco routers and the like work similar to home routers, but they are more advanced and complex and are usually just built for routing. The reason you don't see these in homes, other than the insane cost is that they are too complex to setup for the average home internet user. Home routers are usually configured through a web interface, and more recently, an app from the manufacturer. Cisco routers don't have this so instead they are configured through commands. You have type in commands in order to setup and configure your router. ISPs have different equipment based their needs/services, but yes they have routers similar to these and even much more advanced and complex systems installed on their data centers and offices. To clarify a bit, if you are setting up a Cisco router, it is known as a CPE (Customer Premises equipment) meaning it is physically located at your business/office, usually in a data room where the connection from your provider comes in.
    2
  15. The computer's network configuration includes the DNS server IP address. When you connect your PC to your home network, it gets a DHCP address. Part of the process is that the DHCP server gives your PC an IP address, subnet mask, and the IP address of the DNS server. That's how it knows where the DNS server is.
    2
  16. Its not the router that hands out IP addresses; Its the DHCP server. In most small home networks, the DHCP server is built-into the router. However, in larger and more complex network, you typically have a few stand-alone DHCP servers. If there's no DHCP server, then your computer won't be able to get a DHCP address. Windows devices use something called APIPA which automatically gives itself an IP address.
    2
  17. There's something called Logical ANDing. This allows the network device to figure out if the IP address in question belongs to that subnet. I don't know how much you know, but it greatly helps to understand the math behind IP addresses, which is binary. If you know how to convert from decimal to binary, it will help you understand IPv4 addresses as well as how ANDing works.
    2
  18. The Cisco Netacad webpage has a decent training course on how to use PT. CertBros and Jeremey's IT Lab on YouTube also have good training videos. Just note that Jeremy's IT Lab's videos are older so the interface may be a bit difference but the core ideas should still be the same.
    2
  19. LMAO. You really think he's going to give out his personal email in these bot/scam infested comments? He'll get bombarded with scammers and people trying to get him to fix their stuff among a myriad of other stuff.
    2
  20. That's one way of thinking about it.
    2
  21. To my knowledge, there's no way to edit the actual entries of the CAM table of a switch.
    2
  22. What exactly do you mean by that? Can you clarify?
    2
  23.  @shaiuken  I see now. It looks like its a public route server. I'm not really familiar with this.
    2
  24. Routers typically have far fewer interfaces than switches. Most routers usually have 2 interfaces: LAN and WAN. You would connect a switch to the LAN interface to get more ethernet ports.
    2
  25. Switches are used to connect devices in a network. Routers are used to connect to other networks.
    2
  26. One thing he doesn't explain is that routers have multiple interfaces. Each interface has its own MAC address. Most routers have at least 2 interfaces: a LAN (for internal network) and a WAN (out to the internet) interface. When your PC sends an IP packet to the router, it sends it to the LAN interface's MAC address. Internally, the router then sends this packet to the WAN interface which it uses its MAC address. and the .38.1 IP is the WAN interface's IP address. In a real network, the WAN interface usually gets a public facing IPv4 address from the internet provider.
    2
  27. Well yes. A router's job is to send/receive IP packets. But you have to understand the OSI model, specifically layers 2 & 3 to understand why we use switches and routers.
    2
  28. Routers usually have 2 interfaces: A LAN interface and a WAN interface and each interface has its own MAC address. When you send a frame from your PC, your PC puts the MAC address of the router's LAN interface as the destination. When the frame arrives at the router, it will then remove its LAN mac address as the destination and move that to the source. It will then add its WAN interface to the destination MAC address.
    2
  29. It doesn't. Switches work at layer 2 of the OSI model meaning they work with MAC addresses and frames. They don't understand IP address (unless we're talking about layer 3 switches, but that's a different topic). When you have PC-1 that wants to communicate with PC-5 (for instance), PC-1 sends a broadcast frame. The switch receives this frame and broadcasts it to the other connected device. The frame basically asks, what is the MAC address of the device with this IP address?" With "this IP" being PC-5's IP. All devices that receive the broadcast frame ignore it except for PC-5. PC-5 then responds to PC-1 with its MAC address. PC-1 then 'learns' this MAC address.
    2
  30. You can set a static IP configuration on the host device or the DHCP server (if enabled) will automatically configure the host device with that information.
    2
  31. It doesn't really matter. Network equipment is very fast. Even if there was a speed advantage, it likely wouldn't be noticeable.
    2
  32. Nope. It won't work that way since private IP addresses are not routeable on the internet. When your PC sends the packet, it will add its (your PC) IP address as the source and the IP address of the web server as the destination. This packet gets sent to the router. The router looks at the packet's information and will remove the PC's IP address from the source and will add its (the router's public facing) IP address as the source. This process happens along each hop until it reaches the destination. So from the web server's perspective, the packet came from your router and not your computer.
    2
  33. You're better off watching Jeremey's IT Lab's videos on YouTube. He goes over in-depth the CCNA exam as well as how to configure Cisco routers and switches.
    1
  34. Not exactly. A router is a dedicated device to just routing. However, most typical home routers are a combo unit of a router, wifi access point, and switch. In the larger networks, routers just for routing packets.
    1
  35. Yes. Those are called layer 3 switches. They essentially act as both a router and switch.
    1
  36. Layer 2 switches don't have IP addresses so they don't understand the concept of IP's. If you have a layer 3 switch, you can setup IP addresses on it, but that's a different topic.
    1
  37. ??
    1
  38. What would be the point of that?
    1
  39.  @sharadverma8792  You're talking about 2 different things. The ARP packet has nothing to do with sensitive information. In theory, yes with the correct equipment and knowledge, you could intercept communications. That's one of the reasons why network hubs aren't used anymore in production environments. Hubs send all traffic to all parts whereas network switches only send it to the intended destination.
    1
  40. What part of the 2nd video are you talking about?
    1
  41. It depends on the IP in question. IP addresses are a layer 3 concept.
    1
  42. You have to understand the OSI model, specifically layers 1-3. Switches are used to connect devices in a network segment together. A router is used to connect a network to another network.
    1
  43. These types of routers typically have 2 network interfaces. 1 interface connects to 1 network (and has its own MAC) and the other interface connects the other network which also has its own MAC.
    1
  44. He has a PacketTracer Lab file in the description.
    1
  45. Yes, but the main difference is that PC sends a broadcast frame because it doesn't know PC2's MAC address (for instance) and the switch sends that broadcast to all ports; hubs send all frames to all ports regardless of it being a broadcast or unicast message. That's what makes hubs inefficient and practically unused in modern networks.
    1
  46. Which part of the video are you asking about?
    1
  47. Incorrect. Most home routers have a network switch built in. Look at your router. If it has multiple ethernet ports (usually labeled LAN or simply with a number), then that means it has a built-in switch.
    1
  48. ACLs are layer 3 concepts since they work with IP addresses. As such, a switch can't work with ACLs unless you have a layer 3 switch. You can more or less think of ACLs as stateless firewalls. That basically means it allows/denies traffic purely based on IP, IP range, subnet, or port depending on how your ACLs are configured. So yes, it will work as a firewall, but it may be best to have an actual firewall, be it software/hardware.
    1
  49. There isn't one as it isn't the topic at hand. Generally, the router connects to the modem via ethernet cable.
    1
  50.  @JulioCesar-nh3hm  The command prompt on PacketTracer is not full featured. I don't believe there's a way to clear the command line
    1
  51. I'm not entirely sure how to troubleshoot this, but I would first make sure you ahve your internal network setup as well as NAT. You have to keep in mind Cisco routers don't work out of the box; they need to be configured with the LAN network, WAN network, NAT and some other settings.
    1
  52. Yes. You could technically get rid of the switch and plug in the PC directly into the router. In practice, we don't do it this way since networks usually have multiple computers and devices connected to a network. In your scenario, only that PC that is plugged in would be able to connect to the internet.
    1
  53. Yes. That is actually a potential problem. I believe there are some ways to mitigate or prevent it, but I"m not too familiar with them. I'm sure there are plenty of articles online showing how to identify and stop an ARP spoofing attack.
    1
  54. That's correct. I'm assuming its just for demonstration purposes that it shows the ARP info.
    1
  55. Its kind of a gem. The issue I see with his videos is that he explains very good the very beginner stuff. Once you get past the basics, he doesn't go much deeper than that. Its ok to learn the basics, but you will really need to find better resources to learn more. He calls this a CCNA series yet there's hardly any Cisco-specific information. And for the CCNA, it is crucial to know the Cisco stuff. He hasn't even gone over how to setup a Cisco router or switch.
    1
  56. Technically yes. This is known as ARP Poisoning/Spoofing.
    1
  57. That's because ping is a layer 3 concept. The computers have an IP stack which is responsible for network communication. When you ping a PC, your computer sends a packet of data to the destination. In this packet, you of course have the L3 IP address and the L2 MAC address. The switch only sees the MAC address so sends the frame to the respective port.
    1
  58. There are plenty of tutorials online on how to use PT. If you sign up for Cisco Netacad, you can sign up for the PT course which gives you an overview of how to use it.
    1
  59.  @jaiverma3279  Not quite. He goes over that in the next parts. In short, its called ARP - Address Resolution Protocol. ARP maps MAC addresses to IP addresses. Say you have a network of 5 PCs (PC-1 - PC-5). You ping PC-5's IP via PC-1. 1 needs 5's MAC address, but it doesn't know it. PC-1 will send an ARP message. This consists of a broadcast message at layer 2. The switch receives this broadcast message. It basically asks "What is the MAC address of the device with X IP?" Where "X IP" is PC-5's IP address. Since this is a broadcast frame, the switch forwards the frame to all switch ports. However, all devices (except PC-5) will drop the frame since they aren't the intended recipient. Only PC-5 will accept it and respond to PC-1 with its MAC address. PC-1 receives this response and will store the IP and MAC address in its ARP cache. After PC-1 stores PC-5's MAC address, it will send the ping packet. It now knows 5's MAC address and will send it only to that MAC address. PC-5 will receive this ping packet and respond accordingly. The network software of computer systems allow them to respond to pings and other network requests even if there is no router.
    1
  60. Typically, that's your router. However, it usually forwards DNS requests to your internet provider's DNS servers.
    1
  61. I don't really know of any alternative. I strongly suggest getting even a cheap and basic laptop to run Packet Tracer.
    1
  62. What specific part of the video are you asking?
    1
  63. Well you would need to know beforehand the IP address of the computer you're trying to ping. If you don't know the IP, you would use the hostname and then your PC will lookup the IP address of that other PC via DNS.
    1
  64. Yep. Hubs broadcast every single frame to every single port whether or not the frame is intended to be a broadcast frame. Switches only send broadcasts when they receive a broadcast frame.
    1
  65. Both devices are important in a network. A router's job is just to route IP packets to and from their destination. Routers don't have many network ports. So if you need more than 4 ports (what a standard home router has), you need a network switch. In larger networks, you need switches since stand-alone routers are just that: routers. They only have a few network ports.
    1
  66. It just doesn't work that way at least with IPv4 addresses. That's how things were designed decades ago.
    1
  67. You're better off looking at other videos like David Bombal or Jermey's IT Lab. NetworkChuck is a good presenter, but his video series is far, far from complete.
    1
  68. Not to burst your bubble, but this video series is not complete. There is still a substantial of information that he hasn't gone over which is critical to understand for the CCNA exam.
    1
  69. That's above the scope of this video, but I believe there are ways to mitigate or prevent ARP poisoning/spoofing. I think one way is to set static ARP entries.
    1
  70. Not quite. A modem's job is to connect your network to your provider's network (like a bridge) via phone line (DSL or dial up) or coaxial cabling (cable internet). The router's job is to route IP packets to and from your home network. Modems and routers sometimes look similar which can make things a bit confusing. To add to the confusion, most ISPs will sell/rent/give you a combo unit (usually called an internet gateway or other fancy marketing term) which almost always includes a modem, router, network switch and wifi in one unit. So instead of having a separate modem and router, they combine both into one box.
    1
  71. The purpose of DNS is to map IP addresses and hostnames. It doesn't have anything to do directly with other protocols.
    1
  72. Where in the video are you asking about?
    1
  73.  @abul0ksa  Click on the router in question. In the window that appears, click on the CLI tab.
    1
  74. There's a protocol called DHCP - Dynamic Host Configuration Protocol. In short, a DHCP server automatically assigns devices that connect to the network IP addresses and the other required information. You can manually assign IP addresses to devices. This is known as a manual or static IP configuration. It is typically only done in servers and other network equipment and in medium to large networks. Small home networks and small to medium office networks typically have a DHCP server built in to the router. However, in larger and more complex networks, you typically have dedicated servers for DHCP.
    1
  75.  @nightstar_ken  Yes, but it is based on the interfaces. As I said, the routers typically have 2 interfaces each with their own MAC addresses.
    1
  76. Nope. Still a lot of information missing.
    1
  77. He has a few videos much later in the series that go over MAC addresses and IP addresses. Might be a good idea to check them out.
    1
  78. Do you have any IT experience or experience working with computers? If not, I would probably start with the ITF+ (if you know little to nothing about computers or IT) or the A+ Cert videos if you have some knowledge of computers already.
    1
  79. We've already more or less run out of IPv4 addresses, yet the internet still works. A lot of ISPs have already been using IPv6 for years
    1
  80. Kinda hard to help without details....
    1
  81. lmao. What do you mean? What AV are you using that's telling you that they have malware on them?
    1
  82. Its in the end devices section on the bottom left corner.
    1
  83. Its up to you. For most things, PacketTracer is fine. If you do have the option to buy some older Cisco equipment, I would also use that to learn. That way, you have actual hands-on experience working with the real hardware. Packet Tracer is great for simulating a bunch of different hardware and settings.
    1
  84. They have routing tables that they use to figure out where to send IP packets to. There are a few protocols used by routers to determine the best route.
    1
  85. interface. Its a port (physical or virtual) on a switch or router where you plug in a cable to establish connectivity.
    1
  86. No. The MAC address is only useful inside of the network the PC is in. In other words, Jonny's computer only knows about the MAC addresses of the devices that are in the same network. Since Jonny is on a very different network, it has no way of getting the MAC address of the coffee server nor does it need it.
    1
  87. You're better off using other resources. There's a channel called Practical Networking that has a pretty good Network Fundamentals play list on youtube.
    1
  88. Same thing. Its a combo unit of a modem (for communicating with cell tower), router (routing IP packets to and from your network devices) and a wifi access point (for connecting wifi clients to the hotspot). Routers don't all look the same. Your typical home router looks very different than an enterprise router as does a hotspot device.
    1
  89. You have to understand the OSI layers. Switches are layer 2 devices. They only work with MAC addresses. Routers work at layer 3 which means they work with IP addresses. In most networks, your computer connects to the network switch and in turn, the switch connects to the router. Say you have a network of 5 PCs (PC-1 - PC-5) a network switch and a router. If PC-1 sends a ping to PC-5, PC-1 will create a packet and put in PC-5's MAC and IP address as the destination addresses. The PC sends this packet to the switch. The switch only cares about the layer 2 header and will look at the destination MAC address. It looks in its CAM table to find which port that MAC address is connected to and send it to the correct port. Now, if you send data to a computer outside of your network, say to a webserver, this same process happens, but instead of the packet going to a PC on your home network, it goes to the router. Then the router determines where it has to go and sends it out to your internet provider's network and in turn the internet until it gets to its destination.
    1
  90. One thing to keep in mind with his videos is that he doesn't go as in-depth as he should if we wants to call them "free ccna". He's a good presenter and his videos are pretty good at giving you a high-level overview. Its fine if you're a beginner but when you want to go deeper his videos aren't that great. Just throwing that out there. To answer your question: In most home and small business networks, the DNS server is part of the router. The router does multiple things: routing, switching, wifi access, DHCP server, DNS server, etc. This is for the sake of convenience and simplicity for average home users. In the more complex and larger network environments, there are usually separate devices handling different things. For instance, you can have a router that's just focused on routing, you can have a server dedicated to DHCP, a server dedicated to DNS, and so forth.
    1
  91. Communicate between devices. If you have PC-1 and PC-2, PC-1 wants to talk to PC-2, or communicate with it. It can be something like sending a picture, video, or whatever.
    1
  92. Notice at the top of the video, in the destination section, it says "broadcast". When a device on the network sends a broadcast frame, the switch will broadcast that frame to every single connected device.
    1
  93. Because they're different networks. Johnny's computer is on a separate network than the coffee server. You have to keep in mind that the gateway is the router in your network. Johnny's laptop is not on the same network as the coffee server.
    1
  94. Not to be a downer, but it is extremely unlikely anyone can pass the CCNA just with this video series. He's a good presenter, but his series is extremely incomplete. There are still a lot of topics (and I do mean a lot) that he hasn't covered which are important to not only understand networking, but for the actual exam itself.
    1
  95. I suggest learning how an IPv4 address works. They are broken up into 8 bits (called an octet). The largest number you can make with 8 bits is 255. For the 2nd question, what specific time are you asking about?
    1
  96.  @ahhqq  I'm not sure why that is. I think that's the default behavior on Linux systems.
    1
  97. Cisco routers are enterprise-level routers. They have the same core functionality as your home router, but are designed to work with many more devices and have a lot more features that are largely irrelevant to 99% of home users. Your router does have routing tables, but they are quite small since your ISP is mainly responsible for doing the actual routing. The thing is that most home routers although quite advanced nowadays are also quite limited compared to an enterprise router. Pretty much all modern home routers are a combination of a router, wifi access point, and a network switch. If you look at the back of your router and see 4 network ports, it has a switch. you may not have a dedicated network switch, but you most likely do have a switch built into the router. Home routers also usually have decent web interfaces/apps you can use to setup and manage your network. Enterprise routers don't usually have this. You have to type in commands in order to setup a router, like what its name will be, the interfaces it has, interface-specific settings and so forth. All of that is done through commands; you don't usually have a fancy web interface.
    1