Re: do we support non contiguous netmasks ?

From: Anders Lowinger (anders.lowinger_at_packetfront.com)
Date: 04/06/04

  • Next message: Andre Oppermann: "Re: do we support non contiguous netmasks ?" 
    Date: Tue, 06 Apr 2004 13:15:57 +0200
To: Andre Oppermann <andre@freebsd.org>

    > So far I haven't found any useful application of non-contignous
    > mask in network applications.

    The only reason I've ever heard is when joining two separate subnets,
    for example (sorry my cisco style, i'm a routing guy)

       interface ethernet 0
        ip address 192.168.0.0 mask 255.255.255.0

       interface ethernet 1
        ip address 192.168.2.0 mask 255.255.255.0

    if those are combined on one interface you could write

       interface ethernet 0
        ip address 192.168.0.0 mask 255.255.253.0

    This is normally solved by secondaries (aliases)

       interface ethernet 0
        ip address 192.168.0.0 mask 255.255.255.0
        ip address 192.168.2.0 mask 255.255.255.0 secondary

    which gives the same functionality with contigious netmasks.

    > Currently Luigi has teamed up with me to do the per-if
    > ARP table stuff and the removal of cloning from the routing table.
    > That alone will make network life in the kernel much easier.

    Sounds great! So, what is the goal?
    Will the ARP functions generate host routes instead of the cloned routes?
    During forwarding to a nexthop with unknown L2/ARP entry, will you
    trigger ARP?

    We would really need an Mtrie for faster route lookups and combine the
    forwarding lookup with the check for packets destined to the router/
    connected addresses. The scalability of many L3 interfaces today is not that
    great. (caveeat, not 100% updated on the -current)

    I'll dig around, I have some old mtrie code I could try
    to do some patches for....

    /Anders
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  • Next message: Andre Oppermann: "Re: do we support non contiguous netmasks ?"

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