Remember that in a switched environment the issues change from a
non-switched network. The problem with collisions almost disappears and the
issue becomes broadcasts. When an end-node receives a broadcast it shuttles
the packet up the stack and the NIC issues an interrupt. The problem with
large numbers of broadcasts has less to do with the switch's bandwidth
capacity and more to do with the workstation/server's capacity for handling
interrupts. Too many interrupts and your users are going to be VERY unhappy.
As far as the switch is concerned, generally speaking, the issue is not how
many devices a switch can support locally (after all, we could be hooking
48-port dumb hubs to each 100Mb switch port), but rather how many MAC
addresses can be tracked by the switch (on a per port/trunk, module or
switch basis depending on hardware). If one builds an extremely large
switched network (IBM's campus Xylan network push a few years back comes to
mind) it could be possible to overload a switch with MAC addresses from
other devices in the broadcast domain(s). Available space for MAC addresses
(CAM table etc..) on a per-port basis can also be a limitation, based on
hardware. In either case, if one has more devices than the
switch/module/port can handle, one will see inconsistent frame delivery
between all devices, or complete unreachability of some, depending on switch
behavior in a table overflow situation.
I'd like to hear what effect might be seen in a network using LANE. Since I
haven't worked with it myself I can't say right off hand whether the remote
LANE clients will show up in the local CAM table rather than the ATM
interface. Anyone have the answer to that one?
My $.02,
Karen
*********** REPLY SEPARATOR ***********
On 6/14/2001 at 12:55 AM CCB wrote:
>I have to agree, I would not personally put more than around 200 devices in
>a broadcast domain and that is pushing it. If it is possible I would break
>it into two or more VLANS and route between the VLANS, this help out in the
>performance arena.
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
>Hire, Ejay
>Sent: Tuesday, June 12, 2001 6:19 AM
>To: [EMAIL PROTECTED]
>Subject: RE: Vlans - maximum no of devices [7:8128]
>
>
>The theory behind it is this. Would you, in a preplanned network
>deployment, put over 250 devices in the same Broadcast domain?
>
>-----Original Message-----
>From: John Kale [mailto:[EMAIL PROTECTED]]
>Sent: Tuesday, June 12, 2001 5:45 AM
>To: [EMAIL PROTECTED]
>Subject: Vlans - maximum no of devices [7:8128]
>
>
>hi all,
>
>I read somewhere that there can only be a maximum of 254 devices in a vlan.
>I'm currently redesigning a network that would have a vlan containing about
>300 devices. Is the 254 restriction a design one? Please can someone
>enlighting me on this issue.
>
>
>regards,
>
>
>Tunde
>_________________________________________________________________________
>Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.
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