Troy Aden wrote:
We are currently running 2 Bering 1.0 routers (each with 4 subnets / NICs)A couple of points:
on a network of about 300 systems. We have had no issues with Bering and are
very happy with it. The question is that we are looking at growing our
network significantly in the next year. (Doubling in size is a distinct
possibility.) I am just wondering how many systems I can run off of these
two routers before I start getting worried that they can't keep up. I am
considering re-subnetting the company so that I can get around having a
limit of 253 hosts / NIC.
Here are a few particulars of the hardware.
P133 and a P100 with 64 MB of RAM.
One router is running a 4 port NIC the other 4 3COM NICs.
They are both running DHCRelay so that DHCP requests can get forwarded to
our DHCP servers on one of our subnets.
Should I look at upgrading the RAM / CPU? At what point does this become
redundant? How can I prevent buffer overflow when traffic is high? Is there somewhere I
can go to increase the available memory?
Thanks in advance.
- It doesn't matter how many systems you're running off your routers. What matters is how much bandwidth you're trying to push through them.
The usable bandwidth of a router depends in a general sense on it's bus bandwidth (combined with the "efficency" of it's NIC's...good "server-class" NICs do bus-mastering transfers, and require little or no CPU resources to move data) and it's CPU horse-power. As a general rule-of-thumb, network bandwidth consumes bus bandwidth (with server-class NICs...lower-end NICs consume significant CPU bandwidth just to move data around, which is a bad thing), while packet processing consumes CPU bandwidth. As a reminder, the PCI bus peaks out at 132 MByte/s (about 1 GBit/s), but typical "useful" bandwidths are more like 75-100 MBytes/s (600-800 MBits/s). Divide those useable bandwidth numbers by two if your traffic has to go in/out (ie routed between interfaces), and by two again if you've got an ancient PCI chipset (as you probably do with the P100/133 systems).
- Search the 'net for typical linux performance metrics. You should be able to extrapolate performance for your specific hardware (of course, you can always test your specific setup, and should, if you're concerned about performance in your particular environment).
- I would personally expect a P100/133 class system with good server-class PCI NICs to be able to support up to a few (2-3) saturated 100 MBit/s links without much trouble. If you need full bandwidth on multiple 100 MBit/s links, or are running any gigabit links, I would suggest migrating to a higher performance system, preferrably with fast/wide PCI.
- If your routers are basically providing internet service, and everything is limited by your internet uplink to the 1's or 10's of MBits/s (perhaps with a 100 MBit/s link between them for an office backbone), the Pentium-class systems you describe should be fine, regardless of how many "clients" are on either side of them.
--
Charles Steinkuehler
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