IP routing question

Posted on 2006-04-25
Last Modified: 2010-03-19
Is it possible for an ISP to provide a second subnet (different from the one used on the router serial links) and allow it to be used for externally accessible devices?  If so how is this accomplished?  Can the ISP route the new subnet to the existing one?  Currently we have a /28 subnet on our serials, and we are running out of avaialable addresses for externally accessible devices.  Can they just add an additional /27 subnet without changing the addressing of the interfaces and already configured devices?  Please excuse my ignorance in these matters.
Question by:sstroud98
    LVL 8

    Accepted Solution

    Yes this is possible, the ISP will route the new subnet via the existing addresses.  The router or firewall that you already have must be capable of handling the additional addresses either through NAT or by routing to an attached interface on the device.
    LVL 16

    Assisted Solution

    A word of warning - many ISPs will want you to renumber rather than continue to hand out additional small blocks.


    Expert Comment

    NAT will be the best solution for your need. Going for additional subnet involves cost.

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