Can DHCP be used with a switch?

  • Thread starter Thread starter wizofaus
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wizofaus

I currently have four PC's connected to a router that supports DHCP,
and they are all configured to acquire network addresses automatically.
If I now want to connect 4 more, can I use just a switch (the router
only supports 4 connections), and if so, can I have them all acquiring
automatic addresses, or will I have to assign them manually? All the
PC's are running Windows, are on the same Windows network (running over
TCP/IP) and all require Internet access (via the router, which is
connected to a broadband modem). I don't really see how the router can
automatically assign multiple IP addresses if it only sees one device
connected to it (the switch), but there's almost certainly something I
don't quite understand here.
 
I currently have four PC's connected to a router that supports DHCP,
and they are all configured to acquire network addresses automatically.
If I now want to connect 4 more, can I use just a switch (the router
only supports 4 connections), and if so, can I have them all acquiring
automatic addresses, or will I have to assign them manually? All the
PC's are running Windows, are on the same Windows network (running over
TCP/IP) and all require Internet access (via the router, which is
connected to a broadband modem). I don't really see how the router can
automatically assign multiple IP addresses if it only sees one device
connected to it (the switch), but there's almost certainly something I
don't quite understand here.
Click to expand...

When the router receives a request for an IP address then
it issues the first free address from its pool. It does not matter
how this request is received, whether through its own internal
switch or via an external switch.
 
Your current router is also a 4 port switch. Yes, you can uplink another
switch to it and the router will assign the additional nodes lan ip
addresses. I believe you garden variety router will assign up to 50
addresses
 
I currently have four PC's connected to a router that supports DHCP,
and they are all configured to acquire network addresses automatically.
If I now want to connect 4 more, can I use just a switch (the router
only supports 4 connections), and if so, can I have them all acquiring
automatic addresses, or will I have to assign them manually? All the
PC's are running Windows, are on the same Windows network (running over
TCP/IP) and all require Internet access (via the router, which is
connected to a broadband modem). I don't really see how the router can
automatically assign multiple IP addresses if it only sees one device
connected to it (the switch), but there's almost certainly something I
don't quite understand here.
Click to expand...
The switch will be a transparent device and the PC's will act the same as if
they were connected directly to the router. Just remember that one port on
the router and one on the switch will be used for the uplink so in effect,
if you have 4 ports on each, you will only be able to connect 6 PC's in
total.
 
RBM said:
Unless, you get a switch with more than four ports
Click to expand...

It actually has 16. Anyway, I hooked it all up and it actually worked
perfectly straight away, no re-configuring, rebooting etc. necessary.
I only posted the question because someone else had tried it and it
hadn't worked, so my initial assumption was that the router couldn't
handle DHCP assignments for more than 4 connections, but obviously it
can (I was also thinking that the router somehow cared which physical
port the DHCP requests came in on, but presumably in fact it just
examines the MAC address encoded into each packet).
 
It actually has 16. Anyway, I hooked it all up and it actually
worked perfectly straight away, no re-configuring, rebooting
etc.
necessary. I only posted the question because someone else had
tried it and it hadn't worked, so my initial assumption was
that
the router couldn't handle DHCP assignments for more than 4
connections, but obviously it can (I was also thinking that the
router somehow cared which physical port the DHCP requests came
in
on, but presumably in fact it just examines the MAC address
encoded
into each packet).
Click to expand...

I think one can connect up to 253 devices to a router by adding
switches/hubs.
 
Travis said:
I think one can connect up to 253 devices to a router by adding
switches/hubs.
Click to expand...
But that doesn't imply that the DHCP server built into a typical SOHO
router will be able to serve them all.
 
It's safe to say that various SOHO routers come with different DHCP lease
capabilities. The SMC 7400VBR that we typically use can service all 252
available addresses in any /24 network. You cannot change the subnet mask to
larger or smaller than a /24, although you can specify any network from
1.0.0.0 - 255.255.255.0. The default is to hand out 50 IP addresses from
..100 - .149, but you can set it as you please. Some "subscription-based"
routers like a Watchguard will either (1) only hand out DHCP addresses equal
to the number of licenses or (2) hand out all you want, but only service as
many as there are licenses. It's always best to check out the capabilities
before planning on any configuration.

....kurt
 
CJT said:
But that doesn't imply that the DHCP server built into a
typical
SOHO router will be able to serve them all.
Click to expand...

The User Guide for my Linksys BEFSR41 says it can serve 253.
 
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