SRP547W

[s.vandermeulen]

I am considering purchasing a SRP547W Router but there are a couple of things that I am trying to clear up before I do.

I am hoping that someone here can assist with the following questions:

1. I want to do load balancing using two WAN connections (ADSL2+ and 3G). The admin guide indicates that this is possible, however the USB 3G Modem compatibility guide says this:
   
   Only one interface can be used to establish a link at a time. By default, the SRP uses the wired WAN connection when available. If an Internet connection is already established via the wired WAN port, the USB modem will only be used as a failover connection.
   
   That appears to directly contradict the admin guide so it has me worried. Can someone confirm that load balancing is definitely possible with a USB 3G modem?
   
   
2. On page 42 of the SRP 500 Series (540 Models) Admin Guide it says:
   
   When load balancing is enabled,we recommend that you disable NAT. See NAT,page 73.
   
   However, there is no explanation anywhere as to why it is recommended that NAT is disabled...page 73 simply tells you how to disable it. I need to run NAT, so I need to understand what is impact is of using load balancing with NAT enabled. Can anyone shed any light on this?

I would really appreciate some help with the above. Thanks in advance.

Sebastiaan

[Andrew Hickman]

Hi Sebastiaan,

Regarding your first comment, I believe that this comment is really a legacy of how the first SRP500 products (SRP520) worked.  A 3G modem can certainly be added to the load balancing group.

[Note: failover must be disabled to use load balancing]

Regarding NAT.  It is possible to configure load balancing with NAT, however in this case, remote Internet servers will potentially see sessions from remote hosts behind the SRP500 coming from different source IP addresses (the WAN IP addresses).  This may cause sessions to be reset unexpectedly. 

The SRP500 balances traffic on a per session basis in accordance with a user configurable weighting between WAN interfaces.  A health check feature ensures that a WAN interface is removed from the load balancing group in the event network connectivity is lost for some reason.

Hope that helps,

Andy