What does the Wireless ISP (WISP) "see" when I'm using VPN fromhome?

Discussion in 'Wireless Internet' started by Yaroslav Sadowski, Sep 5, 2014.

  1. Sure. Any IPSEC implementation that does not use AH header
    compression. This explains how it works:
    <http://www.downloads.netgear.com/fi...sics Internet Protocol Security (IPSec).html>
    Note that there are usually two IP headers involved. The encapsulated
    IP header, which contains the LAN IP address, and the external IP
    header which defines the VPN terminating server. The LAN IP headers
    are always encrypted. The external IP (routing) header is usually not
    encrypted. See Fig 3 above.

    If the WISP were sniffing the traffic looking for contract violators
    using his system for commercial purposes but only paying consumer
    rates, he would be most interested in the external IP (routing)
    header, which would be needed in order to connect to the terminating
    VPN server. What is happening on the LAN at either end is of little

    Hint: One of the most common VPN screwups that I've seen is where the
    IP block at both the client and company network use the same Class C
    network block. For example, if the company used 192.168.1.xxx and the
    client used the same block for his local network, there's a really
    good chance that there are going to be duplicated IP addresses when
    the two networks are glued together by the VPN tunnel. This is why I
    like to use goofy Class C (non-routable) IP blocks for home networks.
    My office is 192.168.111.xxx and home is something else.

    Back to fighting with Windoze 8.1. I'm losing.
    Jeff Liebermann, Sep 9, 2014
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  2. Just one question: Did he speak English?
    Well, one more: Did he install seat belts on your chair?
    If you have a split tunnel setup, you get to download your Usenet junk
    on your own dime. If you have a full VPN, which funnels all traffic
    through your employers VPN, he gets to pay for your Usenet junk.
    Somehow, I don't think the IT people will appreciate the traffic. As
    a compromise, you might consider just downloading article headers and
    only reading what is worth reading (like my postings).

    Dilbert, working from home:
    <http://search.dilbert.com/comic/Working From Home>
    Jeff Liebermann, Sep 9, 2014
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  3. Jeff Liebermann, Sep 9, 2014
  4. It was the "encapsulated" headers I was refering to. The others had
    better not be encrypted since they are critical for delivering the
    packet from the vpn client to the server.
    Not clear how sending packets even to a vpn server at your company could
    be considered a vilation.

    Why in the world one would route the local network over the vpn I do not
    know, but I agree there could well be problems if there are duplicate
    addressses on the remote network as on the local one.
    William Unruh, Sep 9, 2014
  5. I think this is the crux of the matter. The statement you have made is
    not correct. The correct statement would be that all traffic from the
    computer goes through the tunnel.

    The problem is that you are familiar with a Citrix product which is not
    actually a VPN, although it provides some VPN-like services in a
    different way. Some people might even incorrectly call it a VPN, but is
    neither a full tunnel nor a split tunnel.

    Scott Hemphill, Sep 9, 2014
  6. Yaroslav Sadowski

    Char Jackson Guest

    The routes related to my employer's VPN have a metric of 1. For the
    addresses that they suck in, (it's a split tunnel), I can't make any
    exceptions because I can't get anywhere near that metric. From memory, the
    best I can do is a metric of 21.
    Char Jackson, Sep 9, 2014
  7. Teh OP has a box which is supposed to be doing the VPN for him. It is
    not clear to me how that box is attached, or what the innards of that
    box are. It could be that that box is simply another computer with an
    address on his local network, which he is supposed to route all his
    company traffic, or all his traffic to. It will take over the job of
    setting up the VPN and the routing. Now I would doubt that the company
    would allow a full tunnel into their site (Ie, allow all traffic from
    his machine to run through the company network) That would seems to be
    as bad a security hole as allowing him to log onto the company network
    from outside. Thus that box might have a routing table which routes
    company IP through that tunnel, and all other traffic through his ISP.
    Or it may have the condition that ONLY traffic to the company is to go
    through that box.

    It will be interesting to see if the company person who is going to set
    it up for him will be totally flummoxed when he sees a Linux machine, or
    come up with a new rule that only Windows and Macs are allowed to
    connect to the company. Anyway it will be interesting to see what
    happens. I hope the OP reports.
    William Unruh, Sep 9, 2014
  8. Sorry. I was using "IP headers" to refer to both the routeable IP
    headers, and the encapsulated headers for the local LAN. Sorry for
    the muddle.

    For the record, the LAN IP headers and port numbers are encapsulated,
    encrypted, and not visible. However, that's not what's important
    here. The OP is trying to determine what the WISP can sniff to avoid
    a rate increase precipitated by a change from consumer to commerical
    service. That will largely be determined by the amount of traffic,
    but also by what he's using the WISP services. Staying connected to a
    VPN server all day long is usually deemed commercial use as it's
    assumed that only business users (and paranoid hackers) use VPN's. I
    vaguely recall (and am too lazy to check) that the AT&T and Comcast
    ToS (terms of service) specifically define using a VPN server as
    commercial use. Yeah, here's a really old reference:
    and it's more relaxed mutation:
    From the AUP at:
    there's no specific mention of VPN, but does mumble that the service
    cannot be used for:
    "use the Service for operation as an Internet service provider
    or for any business, other legal entity, or organization purpose
    (whether or not for profit)"
    I'll assume that the WISP ToS and AUP policies are similar.

    Anyway, the question is whether the ISP can see the VPN server IP
    address, the common VPN ports, and the amount of traffic through the
    VPN. For all 3 questions, the answer is "yep".
    It's not common but is often done where the encryption and
    encapsulation overhead would excessively slow the system down, or
    where security isn't a big concern. For example, I use several
    unencrypted IPsec tunnels to seperate non-time critical traffic from
    various weather stations that all share the same source IP address
    using a shared link where I'm a low priority user. That makes QoS
    much easier to setup and gives me big discount. Actually, I barely
    recall how it's setup as it's been running essentially untouched since
    about 2006.

    Back to doing battle with Windoze 8.0 -> 8.1
    Jeff Liebermann, Sep 9, 2014
  9. That's a different headache. Assuming different Class C IP blocks for
    the local LAN (which I'll call the remote office) and the other side
    of the VPN server (which I'll call corporate headquarters), the idea
    is to make the headquarters LAN visible to the remote offices. To do
    this, each machine connected via the VPN ends up with two IP
    addresses. One is the original local LAN IP address, which is
    assigned by the local DHCP server. The other is delivered from an
    address pool in the VPN server and is on the corporate headquarters
    LAN IP block.

    On the remote office client machines, the big question is where does
    the default gateway point to? For the local LAN, it's easy. It goes
    to the IP address of the local router that connects to the internet.
    However, it can also point to the default router on the corporate
    headquarters LAN if the admins decide that EVERYTHING at the remote
    offices will go through their security system (looking for viruses and
    leaks of confidential information). It can also point to the
    corporate VPN server IP, and do much the same things.

    Want me to diagram it out with example IP addresses? (I'm busy right
    now and don't have the time).
    Jeff Liebermann, Sep 10, 2014
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