QuoteBut if I wished to add another OBi100 or two, can I plug a 5-Port Fast Ethernet Switch into one of the four device outlets and get the extra capacity?
I have never tried that, so others may wish to comment. I suspect we are back to the issues of ports. At default, both your OBi100s are using the same ports, e.g. 5060 as the SIP listening port for sp1 and 5061 as the SIP listening port for sp2 (OBi calls them UserAgentPorts). Any decent router including your Home Hub should sort this out as the two OBi devices are on different private ip addresses. However, I prefer not to leave this to chance. I would change the UserAgentPorts to ports well away from the defaults, something like 34000 and 34001 for UserAgentPorts for OBI1 and 34002 and 34003 for OBi2. This helps to avoid sip scanners who target the usual port numbers. Also, I would change the RTP port ranges increasing the OBi2 ports by 400 to clear them of the OBi1 RTP ranges. These changes would need to be reflected in your port forwarding.
One number you can't change is the OBiTALK listening port, which has to 10000. For this reason, if you wish to try the Ethernet switch solution, I suggest plugging it into one of the Hub outlets that does not have an existing OBi connected.
A lot of this depends on what you are using your OBi devices for. Each OBi100 can support two registered voip providers and up to eight that do not require registration (i.e. outgoing calls only). An OBi200/OBi202 supports four registered voip providers and eight unregistered. However, each only supports one OBiTALK network connection, if that's important to you. If you share your aims, then users here may be able to suggest good configs for you with less OBi devices.