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Eircom unusable static addresses

  • 16-06-2005 3:06pm
    #1
    jimmycrackcorm
    Registered Users, Registered Users 2 Posts: 14,339 ✭✭✭✭


    Thought this was par for the course for Eircom. At work we have Ericom Business BB - i.e. 4mb dsl. with 4 static ip addresses.

    I asked our Comms guy to get the 4 static ip addresses of eircom so we could set up vpns etc. He comes backand tells me that Eircom advised that we can only use two out of the 4 addresses in the range i.e. the middle two.

    Does anyone know why this is as the Eircom biddy didn't know?


Comments

  • #2
    SparkyLarks
    Registered Users, Registered Users 2 Posts: 363 ✭✭SparkyLarks


    jimmycrackcorm wrote:
    Thought this was par for the course for Eircom. At work we have Ericom Business BB - i.e. 4mb dsl. with 4 static ip addresses.

    I asked our Comms guy to get the 4 static ip addresses of eircom so we could set up vpns etc. He comes backand tells me that Eircom advised that we can only use two out of the 4 addresses in the range i.e. the middle two.

    Does anyone know why this is as the Eircom biddy didn't know?

    Is it that one of the IP addresses is that of the Eircom router?? That means that you can set up you VPN on the remaining IP addresses

    I know that should leave 3 Usable IP addresses so I'm not quite sure


  • #3
    Kali
    Closed Accounts Posts: 6,601 ✭✭✭Kali


    That or you have just been allocated a /30 .. one network, one broadcast and two usable ips.


  • #4
    jimmycrackcorm
    Registered Users, Registered Users 2 Posts: 14,339 ✭✭✭✭jimmycrackcorm


    We dont have an eircom router just our own dlink dsl modem/router (no different than that which I sed at home). that has one ip address so that leaves us with one other ip out of the four for our use.

    Whats the "/30" / broadcast addresses and what use are they if you can survive without them with a single address on a home dsl connection.


  • #5
    byrnenj
    Closed Accounts Posts: 566 ✭✭✭byrnenj


    That's the standard for IP ranges. A /30 IP range gives you 4 IP addresses. The first and last are your network and broadcast address, and the middle 2 are the IP's that you can assign to your computer or router or whatever.

    It's called subnetting of IP, and is how ISP can split their huge range of IP addresses into smaller groups allowing customers have a range for themselves.
    IP's ranges come in a single, 4, 8, 16, 32, 64....etc.
    If you need 4 ip addresses you should order 8, because the number will always be that minus 2. So if you order 8, it will be 8-2=6. If you order 16, it will be 16-2=14 and so on.

    Technicaly you do have a range of 4 addresses, but your first and last are reserved for your networks use, because if they weren't your network wouldn't work at all.
    That's just the way it works.

    Hope that helps but if you want to know the in's & out's of it all, Cisco can explain it here:
    http://www.cisco.com/warp/public/701/3.html


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