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  1. #1

    source routing ipv6


    I'm working on a project that attempts to emulate a mobile network that has brought up some unusual routing requirements and I'm not sure there is a good solution. I'm hoping some of you here may be able to help me out.

    The Goal:
    The emulated network requires a primary route AND a backup route from each node to a "control" node. The primary route is chosen using a dijkstra algorithm, and the backup route is to exclude ALL nodes in the primary route (when possible). I would like to route traffic over both primary and secondary routes (UDP over primary, and ICMP "ping" packets over the secondary route). Each node has a single physical interface, and I'm using MAC address filtering via ip6tables to break connections between nodes and the usual "ip - 6 route add [dest] via [node]" to configure the next hop for each leg of the route. Unfortunately, this doesn't work well, because not every secondary route will choose the same next hop to the destination for every source node (as the primary route does). Hence, I need source routing for the secondary route.

    The Issue:
    It appears that ipv6 doesn't support source routing. I followed this guide on policy routing that should allow me to use ip6tables to mark packets based on their protocol (stick an http colon shash slash in front of it - I can't post links):

    However, when I get to the statement:
    $ ip rule add fwmark 4 table 4
    I get a NETLINK error. It appears that "ip rule" isn't supported for ipv6 (here's a post confirming it,
    granted it's old - cached copy - again http colon slash slash):

    Perhaps I'm going about this wrong, but from all the googling I've done, it doesn't appear that I can do source routing as I'd like to. If anyone has a better idea about this, I'd love to hear it.


  2. #2
    FYI, this depends on your kernel options. Make sure you have these enabled in make menuconfig

    Networking->Networking Options->Policy Routing
    Networking->Networking Options->IPv6 Protocol->Multiple Routing Tables
    Networking->Networking Options->IPv6 Protocol->source address based routing

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