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[djm]

Hi, we have a DFL-210 set up with 2 ISPs and Failover setup.

It does appear to be correctly detecting a dropped connection and performing the failover.  The trouble is that it takes up to 20 seconds to achieve the failover.  And even if it fails over much quicker, any existing connection fails and has to be restarted - e.g. we use Remote Desktop over a VPN.  When failover occurs, the Remote desktop drops its connection and we have to start it up again.  This is very time consuming.

When the main ISP comes back up again, the DLink seems to move back to it after a while, and again connections get dropped.  Both our ISP connections are wireless mobile phone based ones.  Both have regular brown-outs.  Every time they do we go through the above.

It essentially makes our Remote Desktop connections unusable.

Is there any way to make the failover "seemless" so that a user will never know when it occurs?

Ideally, it would be even better if both connections were load balanced and always used, and when one drops packets were simply routed via the remaining working one until the other came back.

Or has anyone got any better ideas?

Thanks,

David.

[Fatman]

To be blunt and to the point, there will never be any way to make an ISP fail over "seamless" it is impossible that you wouldn't lose a TCP session during this sort of event.

That said changing the ARP interval or moving to host based monitoring (new to 2.26.00) may provide a more efficient means of detecting link failure in your circumstance.  There are advanced settings there to investigate at the very least.  The settings under Routing->Advanced Settings will certainly prove useful.

Additionally we have access to load balancing across WANs as of 2.26.00, which you may find useful.

[djm]

Thanks for the info.

If we use load balancing instead of failoever and one of the ISP links suffers a brown-out - what happens to any open connections that have sent packets down that WAN link?

The mobile telephone based connections we have seem to have 3-40 second brown-outs.  The connection isn't lost, but no responses are received during the brown-out.  Is it possible to set the balancing up to detect these and use the other connection more or perhaps exclusively during these and then go back to balancing when both are up?

Presumably while both are up it is possible to take advantage of double the bandwidth.

Thanks, David.

[Fatman]

Load balanced links can still failover.

Any connections on a link that gets failed over will be dropped and need to be re-established.  If you need to have connections last past a 3-40 second brown out then your best bet is to ride the brownout as this is less than the standard TCP max retransmit time.  If I was you I would actually adjust my max fails and other failover stats to not fail during a 40 second brownout.

You will get approaching twice the bandwidth, it would be effected by your type and amount of traffic, as well as your load balancing algorithm selected.