Fixup protocol

Discussion in 'Cisco' started by franklin.28@gmail.com, Aug 3, 2006.

  1. Guest

    Hi all,

    Can some explain the correct usage of no fixup protocol dns command..
    will this anyway bring about utilisation of PIX

    Frank
     
    , Aug 3, 2006
    #1
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  2. www.BradReese.Com, Aug 3, 2006
    #2
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  3. In article <>,
    <> wrote:

    >Can some explain the correct usage of no fixup protocol dns command..


    If you use the alias command, then there are -two- effects, one
    having to do with changing the destination IP on -outgoing- packets,
    and the other having to do with rewriting DNS responses. One might
    want the IP destination rewriting without wanting the DNS rewriting;
    if so then you would turn off the DNS fixup.

    If you are using PIX 6.2 or PIX 6.3, then using the 'alias' command
    is not encouraged, and the 'dns' keyword for the 'static' command
    is recommended instead. If you are not using 'alias' and you did not
    want DNS fixups to occur, you would normally just leave out the
    'dns' keyword on the 'static'. It appears to me, though, that there is
    no equivilent to the 'dns' keyword for nat/global commands, so
    you might still need to disable the dns fixup for that case.

    If you are using PIX 6.3, then the dns fixup also checks the length
    of DNS responses, to prevent buffer overflows. When you use
    'no fixup protocol dns' then the length checks are not done, which
    might be important for you (especially if you want your users to be
    able to stream music or videos by using DNS requests to bypass
    restrictions on http accesses.)


    >will this anyway bring about utilisation of PIX


    Sorry, I do not understand that question ?
     
    Walter Roberson, Aug 3, 2006
    #3
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