D-link i2Eye between two Cisco Pix 501's -- premature timeout

Discussion in 'Cisco' started by The J-Man, Jan 8, 2006.

  1. The J-Man

    The J-Man Guest

    Hello,

    My church nationally uses a Cisco Pix 501 as a firewall/router in each
    of its buildings that have a broadband connection. We would like to
    establish a video phone call between two of our buildings for the
    purpose of offering a supplemental gospel instruction class to a few
    members in a remote area that would like to participate despite their
    limited numbers. Locally our budget is limited, so we are experimenting
    with a pair of D-Link i2Eye DVC-1100 wireless broadband video phones for
    this project.

    Each building has an ADSL line with a single dynamically assigned IP
    address. I have assigned the D-Link i2Eye video phones static private IP
    addresses and made static assignments in the Pix to map ports on the
    external interface to coresponding ports on the internal IP. The D-Link
    video phones are H323 compatible, using TCP port 1720 to setup the call
    and TCP/UDP ports 15328 through 15333 to do the audio/video magic. It
    also connects to an LDAP directory server to register itself so that you
    can use the speed dial feature to call the other one without having to
    determine the current IP address, which is helpful considering the
    less-technically savy instructor that will be operating this device on
    the other end. I had to open up all of these ports on the Pix's
    access-list.

    In order to get this device to operate I found that it was also
    necessary to turn on a couple of "fixup" commands for LDAP and H323. I
    also found it necessary to increase the timeout setting for H323 from
    the default of 5 minutes to instead be a few hours, as we will need the
    call to last nearly 2 hours.

    After doing all of this the video phones work and the quality is pretty
    well. However, after a random number of minutes they hang up on each
    other and say the connection was lost. You can immediately redial and
    connect back up, but this is very disruptive. So far I haven't found a
    pattern. Sometimes it'll last as little as 90 seconds. Other times it
    will last over half an hour. I am getting 0% packet loss, and don't
    experience any other connectivity problems besides this.

    I wish the D-Link device would give a better description of why the
    connection was lost. Unfortunately I'm not really sure what I'm trying
    to fix, and am afraid I might be fixing something that's not broken. Are
    there any other settings on the Pix that would be causing the H323
    connection to timeout after a seemingly random number of minutes,
    usually between :05 and :35?

    D-link suggested that I might try adjusting the MTU settings being that
    both connections are through PPPoE over DSL. I found them to be at the
    default of 1500 on the Pix, so I have tried adjusting this to 1492 on
    one end. Doing the same on the other end will be my next step, but I
    will have to go back out there and havne't had a chance yet. I'm not
    really too familer as to sure how H323 handles itself with MTU--will two
    different MTU settings at each end result in different packet sizes for
    the same call, or will the protocal limit itself to the smaller of the
    two automatically?

    I'll keep bumping down the MTU settings at each end and testing this
    thing, but I'm wondering if there are any other things I could have
    overlooked.

    Thanks,

    Jeff Phillips
     
    The J-Man, Jan 8, 2006
    #1
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