Let's say a network admin is provided a /24 IP address and asked to create a network that involves two different subnetworks that are distant to each other. I have learned that I need to assign a subnetwork to the ppp connection. However, I need to be more economical about the number of subnetworks since we need to assign 40-50 host per each subnetwork. Is there a way to assign the rented ppp connection to be in the distant LAN so that I do not use a new subnetwork to assign to the connection of these two networks? PS: I also need to do that because I have a router firewall and as I know, these firewall needs to be assigned an IP from each subnetwork. If I start the new network from the other place, I can more easily give these IPs to the firewall.

  • If this is confusing, I'm using a T1 circuit. Should I represent it with some IP addresses and a subnetwork?
    – Onur
    Commented Jun 9, 2015 at 12:14

1 Answer 1


Yes. IP unnumbered allows for this type of configuration on Cisco devices.

The ip unnumbered configuration command allows you to enable IP processing on a serial interface without assigning it an explicit IP address. The ip unnumbered interface can "borrow" the IP address of another interface already configured on the router, which conserves network and address space.

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    Could you please edit your post to provide more details from the link? To avoid problems with link rot, the community prefers that you quote important content and provide the link as reference whenever possible.
    – YLearn
    Commented Jun 9, 2015 at 17:19
  • @YLearn IP unnumbered. That's the answer. You make participating in this site less enjoyable. Commented Jun 9, 2015 at 17:35
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    Ron, I am sorry you feel that way. This is not my personal viewpoint, but the viewpoint of the SE community at large. I have opened a discussion on meta to get a viewpoint that is more specific to this particular community, so I encourage you to voice your viewpoint there.
    – YLearn
    Commented Jun 9, 2015 at 17:36
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    answer edited to best fit SE style. Commented Jun 9, 2015 at 19:21
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    @RonRoyston If you feel like your question was better as it was, you can always rollback your answer to an earlier revision.
    – Ryan Foley
    Commented Jun 10, 2015 at 19:40

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