How do I force tcp packets to avoid a particular hop?

Discussion in 'Networking, Telephony & Internet' started by ShadowBurger, Jul 1, 2013.

  1. ShadowBurger

    ShadowBurger Member

    Feb 19, 2008

    Does anyone know how one might force packets intended for a particular destination address to avoid being sent through a particular router along the way to its destination? ie take a different route? (there are many routes available in this instance)

    I ask as a server I use regularly is acessed through a regional internet provider local to it. Two of their routers have a loop causing the packet to max out TTL hopping back and forth between them, meaning I can't access the server I'm after at all. Other people can access it fine, but their tracert's are showing they don't go through those routers.

    I'm on Win7

  2. Gunna

    Gunna Member

    Dec 25, 2001
    TCP packets are encapsulated into network frames that are handled by layer 2 devices, you cannot specify the route frames take unless you have control over the devices handling those frames.

    A layer 2 device doesn't care about the end destination the TCP packet is bound for, it only cares about the next device it needs to hand those frames to so it uses MAC address to find the device it is ment to send to, sends the frames and once it has finished and received an ACK for all the frames it gets busy with the next task.

    You could try going through an offsite proxy who uses a different ISP to see if it causes the data to route a different path though
    Last edited: Jul 1, 2013
  3. Heywood

    Heywood Member

    Dec 25, 2001
    IP does allow for source routing (read up on LSRR if you are interested) but some consider this a security risk and is in a lot of circumstances firewalls etc drop packets with those options set so it's not necessarily going to fix your problem.

    Some kind of proxy server that is on the other path is a short term fix but sounds like a pain to set up and to ensure its on the right path.

    The better long term fix is to report a fault although this is probably a long and boring endeavour to get to someone that has the capability to understand your problem, diagnose the fault and instigate corrective action - who knows what other services are also broken that may get sorted when this is resolved? If you're able to include a copy of your traceroute with the ticket you raise, hopefully your ISPs technician will be able to identify and attempt to fix the issue in short order.
  4. evilasdeath

    evilasdeath Member

    Jul 24, 2004
    There are methods to control paths in IP routing, however for the example presented being the internet, it is not possible for the end host to control the path.

    However if you do control another host that does have connectivity you can build a tunnel to the host that does have connectivity, a proxy server does this also.

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