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Thread: In preparation to write my CompTIA A+ Certification....

  1. #11
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    Re: In preparation to write my CompTIA A+ Certification....

    Quote Originally Posted by CharlesA View Post
    DNS is used for name resolution. That doesn't mean it is limited to strictly web servers or web traffic. Depending on how your network is set up, you can either use broadcast for name resolution (messy on large networks) or have a server holding a catalog of all the hosts on the network and forwarding requests to external DNS servers if they do not have a record other host being accessed.
    So default gateways have both a unique IP address along with a unique domain name in human readable format like websites on the www? Do ISPs have DNS servers assigning human readable addresses resolved to each unique IP address to every device below every default gateway (on every subnet of a given LAN) that access the greater global WAN?

    On FreeNode some users have scripts running to mask the identification associated with their domain name. In place of their domain name they have [user]/unaffiliated/. What am I talking about? Is this relevant?

    If you have a static IP, you would need to configure the DNS servers, otherwise the machine won't know who to talk to to resolve host/domain names.
    The IP address of a localhost is either dynamic (requested with dhcpcd on Linux) or static (entered by the sysadmin manually). The same is true for default gateways and subnet masks. Is that accurate?
    Last edited by Drone4four; May 27th, 2013 at 11:26 PM.
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  2. #12
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    Re: In preparation to write my CompTIA A+ Certification....

    Quote Originally Posted by Drone4four View Post
    This is why it's a good idea to wear a an anti static strap when replacing RAM, but a bad idea to wear such a strap when replacing a PSU. Is this accurate?
    No, you should always wear an anti-static wrist strap when handling electronics. You shouldn't be touching any live high voltage components whether you're wearing a strap or not. The straps however do contain a large resistor in series so that they don't expose you to the risk of a nasty shock should something go wrong.

    The absolutely crucial point that the original question was hinting at is that you should always double-check that you have unplugged a machine before diving into its innards. ESD is not the main risk here, it's a mains-voltage electric shock you need to protect yourself from. In the case of highly capacitive components you should also wait a few minutes in between powering off and unplugging, to give the stored charge in the caps time to leak away. Those suckers can bite.

  3. #13
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    Re: In preparation to write my CompTIA A+ Certification....

    Quote Originally Posted by Drone4four View Post
    So default gateways have both a unique IP address along with a unique domain name in human readable format like websites on the www? Do ISPs have DNS servers assigning human readable addresses resolved to each unique IP address to every device below every default gateway (on every subnet of a given LAN) that access the greater global WAN?
    A gateway is just a router, which as the name says routes packets to their destination. They usually have an ip address and domain name, but as they are just moving packets from one network to another, they aren't normally accessible via your web browser or whatnot.

    ISPs host their own DNS servers, and there are third party DNS such as Google's DNS, or OpenDNS that you can use. They all should pull from the same set of records.

    [quote]On FreeNode some users have scripts running to mask the identification associated with their domain name. In place of their domain name they have [user]/unaffiliated/. What am I talking about? Is this relevant?

    That has nothing to do with internet routing or DNS. It is a "cloak" set by one of the freenode staff to hide the public address a user is connecting from. Helps with privacy (or it should, at least).

    The IP address of a localhost is either dynamic (requested with dhcpcd on Linux) or static (entered by the sysadmin manually). The same is true for default gateways and subnet masks. Is that accurate?
    Yes. Usually DHCP will assign the ip address, subnet mask, default gateway and whatever dns servers are configured. If you are setting a static IP, you would need to configure those as well.
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    Re: In preparation to write my CompTIA A+ Certification....

    I'm back looking for some additional clarifications. I wholeheartedly appreciate all the feedback I have already received.

    Chapter 15, Question #10 reads as follows:
    You are running Ethernet cable for a business customer in a building under construction. The cabling on the floor you’re working on is being brought down from the plenum space through a column in the center of the room as shown in the accompanying illustration (see attached). The floor you are working on is 600 ◊ 600 feet. You know that Ethernet cable has a length limitation before you have to start using switches or repeaters. Assuming the column is the starting point, how many repeating devices will you need to sufficiently cable this floor so that all of the cubicle areas in the diagram will be able to be sufficiently wired?

    A. Zero. If you’re starting the cabling at the center of the room, each cable length from the center should be sufficient.

    B. Two. Cable lengths to the two areas on the right should be sufficient, but the two areas on the left are too far away.

    C. Four. Although cable lengths seem sufficient, remember, you’ll be routing cables into numerous different individual cubicles, so the length won’t be straight end-to-end.

    D. Eight. You’ll need two switches or repeaters in each cubicle area, since the maximum effective length of each Ethernet cable segment is only 50 metres.
    I understand how ethernet cables have length limitations. The 802.11 Wi-Fi standard has an estimated outdoor range of ~125 metres and an indoor range of ~50 metres. But this question in particular isn’t about Wi-Fi ranges. The question is about Ethernet cabling. All my companion book by Holcombe says about the limitations of Ethernet cabling is that “An Ethernet NIC will need to connect to the LAN using UTP CAT5/5e/6 cabling that has RJ-45 connectors and does not exceed the 100 metre distance limit between the computer and the switch for UTP and STP.” Pyles’ In-Depth answer verifies Holcombe’s statement that the maximum effective cable length for Ethernet is 100 metres. What I don’t understand is how in C there apparently will be cables routed “into numerous different individual cubicles, so the length won’t be straight end-to-end.” If this is true, then the Ethernet cables wired into each room will sometimes be curved or bent, meaning that some Ethernet cables won’t be able to reach the cubicles placed at the farthest corner of a given room. Does that mean that switches or repeaters should be deployed? If this is true, then D seems more correct than C on that assumption, HOWEVER D can’t be true because factually speaking, Ethernet cable segments are 100 metres, not 50. Therefore, all the answers choices are wrong by my judgement. The In-Depth answers go into detail about how C is the correct answer. Here is exactly what the In-Depth answers say about C being correct:

    The maximum effective cable length for Ethernet cable is 100 metres, or about 328 feet, and if you are running cable from the centre of the room to the edges, you shouldn’t need repeaters or switches, but you will also be using a lot of cable length conforming to the position and shape of all of the individual cubicles in each area. Accordingly, you’ll likely need one device per major quarter of the floor to make sure all of the cubicles can be networked.
    What is the author of this practice answer trying to say here? What device? A device such as a host, like a computer with a NIC? I should hope so. Connecting devices to the WAN through the LAN is the whole purpose of the project described in this question. Why does this In-Depth answer indicate such a trivial thing (that you’ll need one device per major quarter of the floor to make sure all of the cubicles can be networked)? Is this device that the author speaks of here the switch/repeater that I spoke of earlier? Is the author out to lunch? If not, then what am I missing?
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    Last edited by Drone4four; June 6th, 2013 at 11:29 PM. Reason: added proper introduction
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    Re: In preparation to write my CompTIA A+ Certification....

    Sounds like they are saying you might need to use one switch per area because of the way the cubicles are set up.

    I have always tried to explain the 100 meter limit is from power to power. Anything that provides power - router, switch, hub, computer can extend that range.
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    Re: In preparation to write my CompTIA A+ Certification....

    Quote Originally Posted by CharlesA View Post
    I have always tried to explain the 100 meter limit is from power to power. Anything that provides power - router, switch, hub, computer can extend that range.
    Thanks, Charles. I think this tip about how power is the limiting factor when it comes to distance.

    Now here is a question I came across in Chapter 16 (Troubleshooting Networks)

    Question #2:
    You have just installed a new network printer in a customerís office. You connect your laptop to the printer using a USB cable, and it prints fine. However, when your customer attempts to connect and print over the network, he canít do so. You check the computerís network configuration and physical network connections, and everything is fine. You check the IP address youíve given the printer as well as its physical connections, and they are correct. You try to ping the printerís IP address from the customerís computer, but the request times out. Of the following, what could be wrong?
    A. The printer is configured to use the wrong DHCP server.
    B. The printer is configured to use the wrong DNS server.
    C. The printer is configured to use the wrong NAT server.
    D. The printer is configured to use the wrong subnet mask.
    I picked C because I didnít really know what NAT was. According to the In-Depth answers:
    A subnet mask defines the specific network to which an IP address belongs. It is expressed similarly to the way an IPv4 address is expressed. A common subnet mask is 255.255.255.0. If this setting is missing or entered incorrectly onto a device that has a manual network configuration, the device will not be able to to be reached over the network.
    So what would be the solution if I were troubleshooting this problem with a printer that was having difficulty connecting to a linux box? If the problem is that the subnet mask isnít set to 255.255.255.0 (letís say itís incorrectly set to 0.0.0.1), would the solution be for the technician to manually set it to 255.255.255.0? If this is what needs to be done, which configuration file and where would you enter this information using Linux? The In Depth answers furthermore say that
    DHCP doesnít assign addresses to printers.
    So where do I go to manually assign a printer its IP address?
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    Re: In preparation to write my CompTIA A+ Certification....

    I haven't run into any devices that do not work with DHCP. That includes, servers, workstations, smartphones, printers, and retail gear.

    But yeah, the subnet mask is the correct answer, but most techs are smart enough to know what the network's subnet is supposed to be set to so they shouldn't make that mistake in the first place.
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    Re: In preparation to write my CompTIA A+ Certification....

    Quote Originally Posted by CharlesA View Post
    But yeah, the subnet mask is the correct answer, but most techs are smart enough to know what the network's subnet is supposed to be set to so they shouldn't make that mistake in the first place.
    Most techs know what the network's subnet is. But where and how do they set this for a printer?
    Last edited by Drone4four; June 16th, 2013 at 03:04 AM. Reason: grammar fix
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    Re: In preparation to write my CompTIA A+ Certification....

    Another issue is the standard supported by each device. If possible, for each wireless network installation, select NICs and WAPs that comply with the exact same Wi-Fi standard. Even though 802.11g, which is faster than 802.11b, is downward compatible with the slower standard, even a singly 802.11b device on the wireless network will slow down the entire WLAN.

    This says that if there is one device which is of a lower WLAN standard, then all devices would tend to use the lower standard thus reducing the throughput on the entire WLAN. The Wi-Fi standards have increasing speeds with each versions a/b/g/n. Even if they are downward compatible but then, one slower standard device would cause other faster (higher) standard devices to run with the slower device's speed.

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    Re: In preparation to write my CompTIA A+ Certification....

    Quote Originally Posted by ppv View Post
    This says that if there is one device which is of a lower WLAN standard, then all devices would tend to use the lower standard thus reducing the throughput on the entire WLAN. The Wi-Fi standards have increasing speeds with each versions a/b/g/n. Even if they are downward compatible but then, one slower standard device would cause other faster (higher) standard devices to run with the slower device's speed.
    So if I connect my slow Kyocera RISE smartphone to my home WLAN, would that bring down/drag down all the download speeds of all the laptops?

    Iím not sure exactly what the Wi-Fi standard is of my smart phone device and I donít know how fast my wireless router is, neither do I know what standard the laptops are on my WLAN. What I know for sure is that my cell is really slow (1Mbps down) and my laptops consistently download at 12Mbps. Accessing the WLAN with my cell doesn't slow down my laptops.
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