upload and download to two different providers....

Discussion in 'Cisco' started by Captain, May 27, 2004.

  1. Captain

    Captain Guest

    I have 2 internet connections,(to two different

    One a dsl connection.

    One a T1 connection.

    By using the assigned IPs from the dsl provider,
    and specifing the T1 for outbound traffic, I see
    all uploads going out the T1, and all the incoming
    traffic coming back on the dsl link.


    Does this type of setup cause any problems or issues?

    Is this a reasonable why to manage traffic?
    Captain, May 27, 2004
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  2. Many providers perform anti-spoofing filtering, by blocking traffic
    coming from a customer that has source addresses not assigned to that
    customer (this can be automated easily by using Cisco's "ip verify
    unicast reverse-path" configuration command). If this is working, your
    T1 provider obviously doesn't do this, but they might decide to add it
    in the future. You'll need to let them know what you're doing so they
    can disable the filter.
    I'm not sure why you need to do it this way. The T1 is full duplex, so
    outbound traffic doesn't interfere with inbound traffic. Is your DSL
    faster than T1?
    Barry Margolin, May 27, 2004
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  3. Captain

    Captain Guest

    Would I just have to worry about my T1 provider, or would anyone
    upstream block me out,(ie. could I have trouble connecting to
    certain networks, or webservers somewhere out on the Internet,
    because of this type of anti-spoofing checking)?

    Yes it is.

    And in the future our needs will be for even more download bandwidth,
    whereas our upload is fine where it is.

    Anotherwords, I'm looking at this type of setup so that I can add
    additional cheaper "download" bandwidth without incuring the high
    costs of adding more expensive T1's to our network.
    Captain, May 27, 2004
  4. You generally only have to worry about your immediate upstream provider.
    Although their upstream provider could have anti-spoofing filtering,
    it's unlikely because ISPs are usually multi-homed, so their upstream
    providers already know that they'll be sending traffic using their other
    provider's addresses. Servers can't do this anti-spoofing because they
    don't have access to providers' routing tables.
    Barry Margolin, May 27, 2004
  5. Captain

    Captain Guest


    I tried this, and everything looked good, UNTIL, people reported
    problems logging into and picking up their e-mail from rogers.com.
    Captain, May 30, 2004
  6. I still doubt it has anything to do with your asymmetric routing.
    You'll need to get on the line with your ISPs (perhaps both of them at
    the same time, if possible) to troubleshoot it.
    Barry Margolin, May 31, 2004
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