I replaced an old router with a new Draytek 2830 Dual WAN router. Immediately remote users started complaining that their Outlook was coming up with the "Connection to Microsoft Exchange has been lost" messages - that disappear after a few seconds.

I've tried various things -
Changing the load balancing settings so that all traffic from the Exchange server goes through WAN1 on the router

Changing the load balancing settings so that all traffic from the Exchange server goes through WAN2 on the router

Changing the external address for the outlook anywhere clients so that it comes in through WAN2


I'm pretty confident that it's something to do with the router - we never had these problems before. Having a little look around I'm wondering whether it's something to do with packet size? But we're getting to a technical understanding that's possibly out of my league

Might be MTU, check DoS protection, fragmented packet protection, any type of content filtering enabled, er... can you put the old router back on to compare ?

Thanks for the reply - been banging my head against a brick wall on this one

Yep - Old router fixes it instantly

I've tried changing ppp_mss to 1300 (from 1442?) - made no difference
Changed mtu and mtu2 to 1400 (from 1500) - made no difference

DOS defence isn't enabled, no content filtering ...

Can't find anything on fragmented packet protection?

Interestingly, on RDP'ing from home to a machine in the office, I noticed the connection would become unstable every few minutes and freeze - so I tried RDP'ing through the other WAN's IP address .... when one would freeze - both would freeze, so it seems less of a network / connection issue and more a router issue itself. We've noticed the internet responding slowly occasionally in the office but dismissed it as some kind of DNS issue.

Thanks, Adam

Not sure then, sorry. I'd raise a support ticket and get it looked at formally.

OK - well thanks for your help!

I emailed Draytek and got this as a response:

Thanks for the e-mail. Draytek router use standard http & https port for their management.It is recommended that you should changes these management ports if doing port forwarding to other device in network.Have you changes the HTTPS management port on router?

What on *earth* has that got to do with anything? I have a feeling this router is going to to be put in its box and sent back ....