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Thread: Subnet question

  1. Senior Member boxerboy1168's Avatar
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    #1

    Default Subnet question

    output

    Switch(config-if)#ip address 10.1.51.0 255.255.255.0
    Bad mask /24 for address 10.1.51.0

    now when I

    Switch(config-if)#ip address 10.1.51.1 255.255.255.0

    it allows me to add that ip address to my vlan on a 2960 in packet tracer however if I

    Switch(config-if)#ip address 10.1.52.0 255.0.0.0

    it will accept that IP address. I find this weird because on the CBT Nuggets videos I am watching the instructor is always using the /24 CIDR value as the subnet rather than the /8 value.

    Why??
    Currently enrolling into WGU's IT - Security Program. Working on LPIC (1,2,3) and CCNA (and S) as long term goals and preparing for the Security+ and A+ as short term goals.
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  2. SS
  3. Senior Member
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    #2
    Hello Boxerboy.

    There's probably others who can give you better answer then me. Off the top of my head it looks like your setting an ip address for an interface and the address your assigning it has no host bits present with the mask your using. An interface cannot have a network address only.

    I'm actually quite confused by what your doing. It's a layer 2 switch so why the layer 3 interface? Unless it's interface vlan1 or something for ssh connections ect. It would help if you gave some more context on what you've already done and what your trying to do now on your switches.

    On a side note I like packet tracer too, but sometimes it just doesn't cut it. Have you considered trying GNS3? The fact you can use wireshark in it really helped me troubleshoot configuration problems. There are ways to do switching in GNS3 too.
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  4. Junior Member Registered Member
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    Jan 2018
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    #3
    10.1.51.0/24
    First usable IP is 10.1.51.1 and last usable IP is 10.1.51.253 as 10.1.51.0 is your network ID and 10.1.51.255 is broadcast ID. That is why the switch errs out.

    In the /8 configuration, that would be a very large subnet if you planned to use all those IP's at once. In this case your first usable IP would be 10.0.0.1 and last usable IP would be 10.255.255.254. That is why the switch accepts that ip as the gateway for that VLAN.

    Sorry correction, last usable IP the /24 would be 254 and not 253. I'm used to using 254 as my gateway address.
    Last edited by networker050184; 01-05-2018 at 01:24 PM.
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