Dear Sir,
The bandwidth issue with your secondary WAN connection could be due to the following:
1) The WAN link itself is slow or is being saturated with other traffic. We will need to check if there are any WAN load balancing/multi-WAN or policy based routing rules in your firewall.
2) There might be some specific firewall rule for this link that is restricting traffic. This can be due to strict rules that are processor intensive. Or a "quality of service" or "traffic Management" rule that is reducing the link bandwidth.
3) WAN link itself is very slow. This could be due to lower speed interface on firewall or the ISP's Customer Premises Equipment or even a interface communications setting mismatch between the two devices, such as the speed settings and the half-duplex and duplex settings. This can also be due to the use of a lower category cable between the devices like "CAT5" cables.
4) Secondary ISP WAN link is asymmetric link i.e. the Downlink bandwidth is always higher then the uplink bandwidth. If this is the case, then you will need to renegotiate the WAN link contract with the ISP for a higher uplink bandwidth.
I am a IT Networking and Security engineer and have experience with WatchGuard, Sophos, SonicWALL firewalls.
I have worked with SonicWALL TZ250 and NSA 2400 firewalls.
If given the opportunity, I can check and implement the required solution as soon as possible.
For further discussion, please message me on the freelancer chat app.
Regards,
Ashley