Router advice needed

Discussion in 'Cisco' started by S W, Jun 18, 2007.

  1. S W

    S W Guest

    Hi,

    Recommendations please for a router that will help me get more IP addresses
    on the network?

    LAN currently is 192.168.10.0
    2 additional networks (VPN) using 192.168.60.0 and 192.168.100.0
    I need more IP addresses on the LAN.
    I've got a likely candidate to move onto the new range in the form of a
    comms cabinet that servers an office with about 40 PCs. I thought if I put
    that lot onto another range , eg 192.168.25.0 that will free up 40 in the
    192.168.10.0 range.

    Question is which router? It has to be configurable through a web interface,
    quick to set up, and not too dear. It has to be able to act as a DHCP server
    to the PCs in that part of the site, but not anywhere else.

    Your input would be appreciated,

    Thanks,
    S
    S W, Jun 18, 2007
    #1
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  2. S W

    Eric Guest

    On Mon, 18 Jun 2007 15:40:48 +0100, "S W" <> wrote for the entire
    planet to see:

    >Hi,
    >
    >Recommendations please for a router that will help me get more IP addresses
    >on the network?
    >
    >LAN currently is 192.168.10.0
    >2 additional networks (VPN) using 192.168.60.0 and 192.168.100.0
    >I need more IP addresses on the LAN.
    >I've got a likely candidate to move onto the new range in the form of a
    >comms cabinet that servers an office with about 40 PCs. I thought if I put
    >that lot onto another range , eg 192.168.25.0 that will free up 40 in the
    >192.168.10.0 range.
    >
    >Question is which router?


    Why not just expand your local subnet, like to 192.168.8.0/21? Leave the default
    gateway at 192.168.10.1 and change your DHCP server to hand out new addresses, or at
    least revised subnet mask. Then change the static-assigned subnet masks on your old
    machines at your leisure. Router not required, just a decent L2 switch.

    - Eric
    Eric, Jun 18, 2007
    #2
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  3. S W

    S W Guest

    "Eric" <> wrote in message
    news:...

    > Why not just expand your local subnet, like to 192.168.8.0/21? Leave the
    > default
    > gateway at 192.168.10.1 and change your DHCP server to hand out new
    > addresses, or at
    > least revised subnet mask. Then change the static-assigned subnet masks
    > on your old
    > machines at your leisure. Router not required, just a decent L2 switch.
    >
    > - Eric


    Hi Eric,

    Thanks for your input.
    Sorry but you've lost me on a couple of points, could you explain in laymans
    terms why I'd have to hand out new addresses on the dhcp server OR a revised
    subnet mask (You mean 255.255.0.0 instead of 255.255.255.0?)
    And what would I do with the decent L2 switch?
    Sorry again, but I'm obvioulsy no network expert!!!

    Steve
    S W, Jun 18, 2007
    #3
  4. S W

    S W Guest

    "Eric" <> wrote in message
    news:...
    > On Mon, 18 Jun 2007 15:40:48 +0100, "S W" <> wrote for the
    > entire
    > planet to see:
    >



    > Why not just expand your local subnet, like to 192.168.8.0/21? Leave the
    > default
    > gateway at 192.168.10.1 and change your DHCP server to hand out new
    > addresses, or at
    > least revised subnet mask. Then change the static-assigned subnet masks
    > on your old
    > machines at your leisure. Router not required, just a decent L2 switch.
    >
    > - Eric
    >


    Hi Eric,

    I did some reading about what you said,
    this website was useful http://www.subnet-calculator.com/cidr.php
    Doing what you suggested will give me over 2000 addresses. I can change the
    DHCP servers no problem, then I'm in business!
    Thanks a lot for your advice.
    I'm still not sure why you say I need a decent L2 switch?

    Thanks,
    Steve
    S W, Jun 19, 2007
    #4
  5. S W

    Trendkill Guest

    On Jun 19, 3:54 am, "S W" <> wrote:
    > "Eric" <> wrote in message
    >
    > news:...
    >
    > > On Mon, 18 Jun 2007 15:40:48 +0100, "S W" <> wrote for the
    > > entire
    > > planet to see:

    >
    > > Why not just expand your local subnet, like to 192.168.8.0/21? Leave the
    > > default
    > > gateway at 192.168.10.1 and change your DHCP server to hand out new
    > > addresses, or at
    > > least revised subnet mask. Then change the static-assigned subnet masks
    > > on your old
    > > machines at your leisure. Router not required, just a decent L2 switch.

    >
    > > - Eric

    >
    > Hi Eric,
    >
    > I did some reading about what you said,
    > this website was usefulhttp://www.subnet-calculator.com/cidr.php
    > Doing what you suggested will give me over 2000 addresses. I can change the
    > DHCP servers no problem, then I'm in business!
    > Thanks a lot for your advice.
    > I'm still not sure why you say I need a decent L2 switch?
    >
    > Thanks,
    > Steve


    Because a broadcast domain of 2000 machines can represent a lot of
    traffic for processing. If you are only putting a few hundred
    machines, you should be fine, but if you have any goal of turning up
    all the addresses in that VLAN, you may be asking for trouble with
    lower class hardware. You just want to make sure your switch can
    support as many ports as you have machines/nodes, but also is prepared
    for the type of network you are placing it in. Generally speaking, I
    have run fairly full /22 networks (1022 addresses give or take), but
    on enterprise class hardware (Cisco 6500s). What you don't want to do
    is have daisy chained switches to support this many nodes, etc, as
    broadcast traffic will kill smaller trunks and tax your switch
    processors. Hopefully this makes sense.
    Trendkill, Jun 19, 2007
    #5
  6. S W

    S W Guest

    "Trendkill" <> wrote in message
    news:...


    > Because a broadcast domain of 2000 machines can represent a lot of
    > traffic for processing. If you are only putting a few hundred
    > machines, you should be fine, but if you have any goal of turning up
    > all the addresses in that VLAN, you may be asking for trouble with
    > lower class hardware. You just want to make sure your switch can
    > support as many ports as you have machines/nodes, but also is prepared
    > for the type of network you are placing it in. Generally speaking, I
    > have run fairly full /22 networks (1022 addresses give or take), but
    > on enterprise class hardware (Cisco 6500s). What you don't want to do
    > is have daisy chained switches to support this many nodes, etc, as
    > broadcast traffic will kill smaller trunks and tax your switch
    > processors. Hopefully this makes sense.


    Hi,

    I will have approx 300 devices on the network for the time being. If 2000
    plus addresses are available, then that should take care of future growth
    for a while.
    I am using basic unmanaged 10/100 switches with a fibre backbone. Most
    traffic passes through two switches (from client to server), some passes
    through three. It could be better, I know.

    What do you mean about switches supporting as many ports as you have
    machines/nodes? Are the Cisco 6500s rated in that way? So I will need a
    switch at the server end that will support 300 machines?

    Thanks,
    Steve
    S W, Jun 19, 2007
    #6
  7. S W

    Eric Guest

    On Tue, 19 Jun 2007 08:54:17 +0100, "S W" <> wrote for the entire
    planet to see:
    <snip>
    >I did some reading about what you said,
    >this website was useful http://www.subnet-calculator.com/cidr.php
    >Doing what you suggested will give me over 2000 addresses. I can change the
    >DHCP servers no problem, then I'm in business!
    >Thanks a lot for your advice.
    >I'm still not sure why you say I need a decent L2 switch?


    Almost any switch will do. Usually medium size, lost cost lans have one switch at or
    near the core that gets the concentrated traffic. If it had some GB/fiber links to
    the edge switches that will do fine. Even trunked 100s will often suffice.

    I think most lans seqments have only a few percent average utilization anyway. You
    could measure yours and see if you have any switch capacity issues. Your traffic
    isn't really changing, only the potential size of your lan. Just for architectural
    reasons it's good to have some extra room in your IP scheme for growth/segmentation.
    If the lan grows substantially, then your L2 backbone will have to grow with it.
    Eric, Jun 19, 2007
    #7
  8. S W

    S W Guest

    "Eric" <> wrote in message
    news:...
    > On Tue, 19 Jun 2007 08:54:17 +0100, "S W" <> wrote for the
    > entire
    > planet to see:
    > <snip>


    >>I'm still not sure why you say I need a decent L2 switch?

    >
    > Almost any switch will do. Usually medium size, lost cost lans have one
    > switch at or
    > near the core that gets the concentrated traffic. If it had some GB/fiber
    > links to
    > the edge switches that will do fine. Even trunked 100s will often
    > suffice.
    >
    > I think most lans seqments have only a few percent average utilization
    > anyway. You
    > could measure yours and see if you have any switch capacity issues. Your
    > traffic
    > isn't really changing, only the potential size of your lan. Just for
    > architectural
    > reasons it's good to have some extra room in your IP scheme for
    > growth/segmentation.
    > If the lan grows substantially, then your L2 backbone will have to grow
    > with it.
    >


    OK, we do indeed have a switch near the core that gets all the traffic. This
    has a gigabit uplink, and I intend to move the servers onto this switch same
    time as I change their subnet masks. I noticed a "blink" in communications
    when I changed one earlier, so its probably better if I warn the users in
    advance, and do them all at the same time.
    Thanks for your advice,

    Best Regards,
    Steve
    S W, Jun 19, 2007
    #8
  9. S W

    Eric Guest

    On Tue, 19 Jun 2007 16:53:38 +0100, "S W" <> wrote for the entire
    planet to see:
    <snip>
    >OK, we do indeed have a switch near the core that gets all the traffic. This
    >has a gigabit uplink, and I intend to move the servers onto this switch same
    >time as I change their subnet masks. I noticed a "blink" in communications
    >when I changed one earlier, so its probably better if I warn the users in
    >advance, and do them all at the same time.
    >Thanks for your advice,


    Just one last thing. The first and most important step when expanding your LAN
    subnet is to change the subnet mask on the router interface that has your default
    gateway IP defined. This means that the router knows about the larger subnet right
    away, and any host with an inconsistent subnet mask that incorrectly sends LAN-bound
    traffic to the gateway router will still have their packet delivered, just detoured
    in and out of the router's LAN interface. Then all the subnets on each of the hosts
    and DHCP servers can be changed without gyrating the whole LAN.

    I'd also recommend that you keep a few /24s of your new range unallocated. Probably
    just start using 192.168.11.xxx and leave the other 6 /24s for the future.
    Eric, Jun 21, 2007
    #9
  10. S W

    SW Guest

    "Eric" <> wrote in message
    news:...
    > On Tue, 19 Jun 2007 16:53:38 +0100, "S W" <> wrote for the
    > entire
    > planet to see:
    > <snip>


    > Just one last thing. The first and most important step when expanding
    > your LAN
    > subnet is to change the subnet mask on the router interface that has your
    > default
    > gateway IP defined. This means that the router knows about the larger
    > subnet right
    > away, and any host with an inconsistent subnet mask that incorrectly sends
    > LAN-bound
    > traffic to the gateway router will still have their packet delivered, just
    > detoured
    > in and out of the router's LAN interface. Then all the subnets on each of
    > the hosts
    > and DHCP servers can be changed without gyrating the whole LAN.
    >
    > I'd also recommend that you keep a few /24s of your new range unallocated.
    > Probably
    > just start using 192.168.11.xxx and leave the other 6 /24s for the future.


    Hi, yes I did do the router/default gateway first. I went live this morning,
    with all the DHCP devices in the 192.168.8.xxx range, leaving everything
    static as is on 192.168.10.xxx
    No real issues, apart from an application that went belly-up. The
    third-party suppliers took about two hours to uninstall/reinstall, I don't
    think I'll ever know if it was because of the subnet mask change or just a
    coincidence!
    I've now got lots of IP addresses free for the future.

    Best Regards,
    Steve
    SW, Jun 21, 2007
    #10
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