Using own router with FTTP router in bridged mode

I am the (volunteer) tech support guy for a small independent school. We have just had FTTP installed by Gigaclear, but we are having difficulties getting it to work with our Draytek 2830 router. The Gigaclear router has been put into bridged mode, and if I connect a laptop directly to it I get the full 100 Mb that the service is supposed to provide. However with the Gigaclear router connected to the WAN 2 port of the Draytek, and the laptop connected by wired Ethernet, speeds are much lower (5-10Mb). Our existing ADSL connection on WAN 1 was disabled when the speed test was run, so it's definitely the Gigaclear speed being measured. I'm guessing that I have not correctly configured the WAN 2 port on the Draytek.

Can anyone provide any advice on how to configure the Draytek router to work correctly with the Gigaclear service? Does anyone have any experience of using an FTTP service with their own router and a bridged ISP router?

So far Gigaclear support has not been at all helpful. Are there any other forums where I might get help?

The Draytek 2830 is a discontinued model, so likely to be pretty old and may not have the CPU and memory to handle routing 100 Mbps of traffic through its NAT interface.

Just because the WAN interface is a Gigabit Ethernet port does not mean the device itself will handle this level of traffic.

Another possibility is that the WAN port is flapping between different Ethernet speeds, so forcing the WAN to 100 Mbps is a place to start without buying more hardware.

Do you mean it is lower by 5-10Mbps, or it goes right down to 5-10Mbps please?

The speed test is showing results that do not go above 10Mb (when connected via our Draytek router) compared with a steady 100 Mb when connected directly to the Gigaclear router.

If the results in the former case had been 90-95 Mb I would have not been concerned!

Have you got the latest firmware on it?

The specs call it an ADSL modem/router, with the fact that WAN2 can be used connected to a VDSL modem the way you have it sort of dropped into the middle of the description. Note the rest of the description is all about ADSL.

The Vigor2830 is our flagship ADSL router/firewall range, winner of the PC Pro wireless router award for three years in a row. This latest series includes support for professional features such as VLAN tagging, Gigabit Ethernet and WiFi (ess models). The Vigor 2830's secondary WAN interface can be connected to other modems now or later (e.g. a second ADSL, a VDSL/BT Infinity or cable modem etc.). Packed with features, the Vigor 2830 offers truly comprehensive ADSL connectivity and security.

Compatible with all variants of ADSL (including ADSL2+ and Annex M) the Vigor 2830 can also be used for cable-modem and leased line applications using its additional gigabit ethernet WAN port.

Link. That suggests to me that the faster speed on WAN2 may be a firmware upgrade from the original.

Note that there are three versions. Single band, dual band and the 2830n v2. If you haven't checked which yours is that you do so before flashing the latest firmware, as there could be relevant differences.

The specs sheet shows all kind of content filtering options, too. Real possibility they are slowing things down so would strip back to a very basic config and build up again

Why do you want to run the Gigaclear router in bridge mode?

We opted to put the Gigaclear router in bridge mode to enable us to continue using our existing Draytek router. This provides more sophisticated facilities for monitoring and controlling use of the connection.

If you were more specific about these facilities of the Draytek router there might be other ways of dealing with them. Some of the managed switches have quite advanced facilities.

Does having double Nat cause much of a problem?

I have never seen a Gigaclear specific forum. There are not many users and putting the router into bridge mode would be an unusual thing to do.

Surely there's no "double NAT" since in bridge mode the Gigaclear router is essentially acting as a dumb modem rather than a NAT router.

Buying a managed switch is an additional expense to do something that our existing kit should be capable of.

I do rather get the impression that we are pioneers in this...