What is VLAN, how it is used?. I have 4 PC's on one LAN co..

Archived from groups: comp.dcom.lans.ethernet (More info?)

What is VLAN, why it is needed?, how it is used in real LAN
environment, what will be the advantage of that?.

Also I have a server, which is sending some special packets over
Network, how can I capture those packets and I need to send those
packets to my application?. It is special packets, how can I
differentiate from regular traffic?. Let me ask this way, if I want to
send special packets to some other client, which is connected over LAN,
how can I send those packets to that.

Thanks.
5 answers Last reply
More about what vlan used
  1. Archived from groups: comp.dcom.lans.ethernet (More info?)

    Santa,
    I would suggest doing some googling on 802.1q for help with VLANs and
    how they work. In very simple terms, 802.1q adds a 4 byte shim to the
    ethernet packet that contains VLAN ID information. This will allow
    802.1q compliant switches to virtualize those packets to their own
    broadcast domain. Others might want to add another 2 cents. Or argue
    with my explanation. (:

    For packet captures, download ethereal and pcap and have fun. Start
    taking captures and put together all the pieces starting at layer 2
    headers and work your way up through the frame. Have fun!

    -mike

    santa19992000@yahoo.com wrote:
    > What is VLAN, why it is needed?, how it is used in real LAN
    > environment, what will be the advantage of that?.
    >
    > Also I have a server, which is sending some special packets over
    > Network, how can I capture those packets and I need to send those
    > packets to my application?. It is special packets, how can I
    > differentiate from regular traffic?. Let me ask this way, if I want to
    > send special packets to some other client, which is connected over LAN,
    > how can I send those packets to that.
    >
    > Thanks.
    >
  2. Archived from groups: comp.dcom.lans.ethernet (More info?)

    Speaking of what is a VLAN...


    How are they used by most switches? Our 3com switch 'learns' the VLAN
    addresses of anything connected to its ports, but theres no way to
    force a port to a VLAN. I thought one purpose of a vlan is security,
    but if I change my IP from 192.168.0.111 to 10.0.0.66 I can jump onto
    the class C address segment because the switch 'learns' my VLAN
    address.

    Is there a list of switches and their VLAN functionality out there?
    Better still is there a specific word describing how to force a VLAN
    on a port?
  3. Archived from groups: comp.dcom.lans.ethernet (More info?)

    Ghazan Haider wrote:
    > Speaking of what is a VLAN...
    >
    >
    > How are they used by most switches? Our 3com switch 'learns' the VLAN
    > addresses of anything connected to its ports, but theres no way to
    > force a port to a VLAN. I thought one purpose of a vlan is security,
    > but if I change my IP from 192.168.0.111 to 10.0.0.66 I can jump onto
    > the class C address segment because the switch 'learns' my VLAN
    > address.
    >
    > Is there a list of switches and their VLAN functionality out there?
    > Better still is there a specific word describing how to force a VLAN
    > on a port?

    Sounds as if you do not have vlans at all. Sounds as if you are simplty
    running multiple IP subnets on the same switch.

    If you did not specify a vlan setup on the switch, then you are not
    using vlans (OK, there ARE ways to do it without configuring the switch,
    but that would assume A) you had network cards on all devices that
    allowed the cards to tag packets, and if you knew how to do that you
    would not be asking the above questions, and B) you would have to have a
    switch that has GARP enabled in it's default config, and I have never
    heard of such)

    VLANS are layer two and have nothing at all to do with IP address.
  4. Archived from groups: comp.dcom.lans.ethernet (More info?)

    In article <1ad1e8b9.0502111059.5e7da2e4@posting.google.com>,
    Ghazan Haider <ghazan.haider@gmail.com> wrote:
    :Is there a list of switches and their VLAN functionality out there?

    There isn't even a list of -manufacturers- of switches, let alone
    of what the details are for particular models.
    --
    vi -- think of it as practice for the ROGUE Olympics!
  5. Archived from groups: comp.dcom.lans.ethernet (More info?)

    In article <1ad1e8b9.0502111059.5e7da2e4@posting.google.com>,
    ghazan.haider@gmail.com (Ghazan Haider) writes:
    >Speaking of what is a VLAN...
    >
    >
    >How are they used by most switches? Our 3com switch 'learns' the VLAN
    >addresses of anything connected to its ports, but theres no way to
    >force a port to a VLAN. I thought one purpose of a vlan is security,
    >but if I change my IP from 192.168.0.111 to 10.0.0.66 I can jump onto
    >the class C address segment because the switch 'learns' my VLAN
    >address.

    Most probable your 3Com does not care about VLANs at all. Although
    there are Switches (namely Xylan/Alcatel) that use protocol based VLANs
    i.e. assign VLAN port mebership (layer 2) according to higher layer
    information contained in the packet, this is not the rule.
    A simple secondary address scheme could be the cause of what you
    encounter.
    The purpose of VLANs is flexibility, efficiency and maybe privacy.
    Security is a state of mind, not of technology.

    --
    Manfred Kwiatkowski kwiatkowski@zrz.tu-berlin.de
Ask a new question

Read More

LAN VLAN Ethernet Card Networking