HR21's second port

Discussion in 'DIRECTV - Coax Networking (private)' started by veryoldschool, Aug 15, 2009.

  1. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

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    I think I'm getting close to what/how this works.
    It will work fine for receivers but not for a router connection.
    During the software download, this port goes "quiet". This seems to have my router waiting for a response from it, that never comes, causing the router to hang.
    Adding a hub, with auto sensing, has the hub disconnect the second port from the router, thus causing it to not hang.
    Resetting the HR21 [without downloading] doesn't cause the router to hang, as the second port comes back sooner than with a download [which keeps the second port "quiet" until the reboot/installing of the software].
    My router will recognize the cable being disconnected, but doesn't during the second port going "quiet", yet my hub does.
    Once the hub has shutdown, when the HR21 reboots, it doesn't have a network connection.
    Moving the router cable to another port on the hub has it show it's active [again], but the HR21's second port doesn't if it's moved.
    "Testing" the network, from the setup menu, returns the network connection, but [first test] fails internet connection. This gets the hub to light up the port on the hub.
    Retesting the network connection [setup] finally gets everything up and running.
    "So", the pass through isn't [doesn't act like] other network connections. You can connect "a slave" to it but not "a master". :shrug:
     
  2. hdtvfan0001

    hdtvfan0001 Well-Known Member

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    Kinda what I saw with my Slingbox tested on the 2nd port of my HR21-200.

    Returned it to its own network connection.
     
  3. Spanky_Partain

    Spanky_Partain Active Member

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    I agree. It acts more like a router port. All traffic is routed through port 1 from/to port 2.

    EDIT
    Might be nice if the documentation from Directv said something like that!

    Port 1 IS the uplink port.
     
  4. hdtvfan0001

    hdtvfan0001 Well-Known Member

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    Agree.

    I've looked at it that Port #2 is more like a "daisy chain" port, contingent upon the overall device being active (first) to make it work properly.
     
  5. dave29

    dave29 New Member

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    The only thing I have used the 2nd port for is to upgrade firmware in my bedroom's BD player. In testing I also ran other H2x-HR2x off of it and it worked fine as well.
     
  6. Tom Robertson

    Tom Robertson Lifetime Achiever DBSTalk Club

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    Technically I think it is a software controlled switch. When the CPU is running the download, BIST, startup, etc. software, the driver for the switch hasn't been loaded into linux yet. (Just guessing based on your description, VOS.)

    And that gives me a tiny bit more insight as to why using both ports isn't good. If linux gets involved with the switching, that would eat significant resources on from the CPU.

    An example of what can happen in Linux--Everytime the CPU has to context switch from a user program to a linux kernal subroutine (like a driver) has a cost. If the switch generates an interrupt to the CPU for each packet--even if the packet is just forwarded, OUCH!

    Normally a switch has a special chip on each port (ASIC) that does almost all the switch work. The switch CPU is almost doing nothing but a bit of housekeeping and letting the ASICs know the current switch table of MAC addresses. (But it doesn't examine packets.)

    If the HR2x is doing more work in the CPU and doesn't have smart ASICs to do the work...

    Now if we had full documentation from Broadcom... :)

    Cheers,
    Tom
     

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