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  1. Senior Member --chris--'s Avatar
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    #1

    Default Reserving IP's via subnetting?

    Is this possible to do?

    I have an instructor this semester that is cool enough to throw us the option of doing a "simulation" question or we can choose to do the question out of the book. I choose the sim since it deals with subnetting and I am eager to get the ball rolling on learning that. Our book has covered the idea of subnetting and summarized key points but we are on our own to figure out how to answer the "simulation" questions if we choose to go that route.

    So that brought me too google an hour ago and now here since I have gone nowhere with google. It appears all the IP reservations are handled either via hardware or via the DHCP server correct? Am I missing something here?


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    #2
    For subnetting there are two options: dynamic (DHCP) or static. You can reserve IP's by excluding them from the DHCP list (ip dhcp excluded-address) doing either a range or adding specific addresses…DHCP will not hand these out. If you are doing static assigning then you just wouldn't use an address.
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  4. Senior Member --chris--'s Avatar
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    #3
    Quote Originally Posted by TechGuru80 View Post
    For subnetting there are two options: dynamic (DHCP) or static. You can reserve IP's by excluding them from the DHCP list (ip dhcp excluded-address) doing either a range or adding specific addresses…DHCP will not hand these out. If you are doing static assigning then you just wouldn't use an address.
    Thats what I thought, which is why I am confused on his question. There are 9 questions, 8 are regarding creating/calculating subnets and then there is the one about reserving IP's. It just doesn't fit in with the other questions or any of the subject matter we have covered.


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    #4
    What I do at home is use x.x.x.0/23 and hand out addresses from x.x.1.1 to x.x.1.254 using DHCP, while keeping x.x.0.1 to x.x.0.254 for static assignment.
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    #5
    I know some consumer routers support "DHCP Reservations", but I don't remember ever seeing them on Cisco routers. "DHCP Reservations" is basically a way of assigning IPs statically from a central point (the DHCP server). The PC's MAC Address is tied to a specific IP Address so that that PC always gets the same IP.
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  7. Senior Member --chris--'s Avatar
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    #6
    Thanks for the help guys, I am emailing him to make sure that's what he means.


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    #7
    I would give us the actual question because we are simply spewing information. For all we know the question could literally ask about the reserved IP address class, which is a specific set of IP addresses and completely different than reserving addresses for a system.
    Last edited by TechGuru80; 11-16-2013 at 10:48 PM.
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  9. Senior Member --chris--'s Avatar
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    #8
    Quote Originally Posted by TechGuru80 View Post
    I would give us the actual question because we are simply spewing information. For all we know the question could literally ask about the reserved IP address class, which is a specific set of IP addresses and completely different than reserving addresses for a system.
    It is not asking for the private IPs/reserved IPs. Here is the question:

    1. The first 10 IP addresses must be reserved for each segment


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    #9
    Based on that question, the answer has to be excluding them from DHCP.

    ip dhcp excluded-address [first ip] [highest ip excluded]
    Last edited by TechGuru80; 11-17-2013 at 09:19 PM.
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  11. Senior Member --chris--'s Avatar
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    #10
    Quote Originally Posted by TechGuru80 View Post
    Based on that question, the answer has to be excluding them from DHCP.

    ip dhcp excluded-address [first ip] [highest ip excluded]
    Thanks, you were right. He said he asked that assuming people that choose that question know DHCP handles this situation. He wanted us to explain how we would "hand out" the IPs.


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    #11
    Right on glad I could help.
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