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what is considered a layer 4 router

clarsonclarson Member Posts: 903 ■■■■□□□□□□
in CCNA & CCENT
would a layer 4 router have to have special hardware to be considered a layer 4 router or is that just something that is implemented in the ios software. It would seem that layer 4 things are like nat and load balancing. Would something like a 2800 be considered a layer 4 router?
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    EdTheLadEdTheLad Member Posts: 2,111 ■■■■□□□□□□
    I imagine a layer 4 router means cef is using layer 4 info for forwarding decisions. I would presume a new asic would be required to take into account the additional info. What hw is supported? good luck reading product array specs icon_smile.gif .
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
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    tuleeohtuleeoh Member Posts: 78 ■■□□□□□□□□
    Never heard the term L4 router before...L2 deals with forwarding MAC addresses (Layer 2 addresses) and L3 deals with routing IP Packets (Layer 3 addresses). There is nothing to route or forward at the layer 4 - the transport layer.
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    Jon_CiscoJon_Cisco Member Posts: 1,772 ■■■■■■■■□□
    I have never heard of a layer 4 router so I goggled it. This is what I found but I have no idea how accurate it is.


    TITLE
    Layer 4 Router

    PUB. DATE
    March 2007

    SOURCE
    Network Dictionary;2007, p281

    SOURCE TYPE
    Book

    DOC. TYPE
    Reference Entry

    ABSTRACT
    A definition of the term "Layer 4 Router" is presented. This refers to a network router that uses the Transport Layer information in making decisions on where to send the packets. Unlike a layer 3 network device, layer 4 router sends incoming packets to one or more machines that are hidden behind a single Internet Protocol address.
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    theodoxatheodoxa Member Posts: 1,340 ■■■■□□□□□□
    The ^^^ sounds like PAT/NAT Overload. I do remember reading about Layer 4 and Layer 7 Switches in my SWITCH studies, which can make decisions based on Layer 4 (TCP/UDP Ports) and/or Layer 7 (Applications).
    R&S: CCENT → CCNA → CCNP → CCIE [ ]
    Security: CCNA [ ]
    Virtualization: VCA-DCV [ ]
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    EdTheLadEdTheLad Member Posts: 2,111 ■■■■□□□□□□
    It's a very simple concept, the layer 4 info can be used to build the cef table for more granular cef switching. People like to make up new expressions like layer 4 router etc etc for marketing.
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
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    Fulcrum45Fulcrum45 Member Posts: 621 ■■■■■□□□□□
    Correct me if I'm wrong but don't all basic home routers NAT and almost all certainly PAT? Just a fancy new expression as previously mentioned it sounds like.
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    TechGuru80TechGuru80 Member Posts: 1,539 ■■■■■■□□□□
    Funny how that article says packets...layer 4 has segments not packets...
    Security Certification Roadmap
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    santaownssantaowns Member Posts: 366
    Sounds a lot like what we call VIPs at work. We use them for load balancing.
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    kianmkianm Member Posts: 8 ■□□□□□□□□□
    Ok this is new to my ears and would like to see credible information about it, otherwise icon_silent.gif
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