AZTCOFW / TECHNICAL GUIDE
MTU Issues
Issues with upload speed frequently end up being issues with the MTU. If the MTU on AZTCO-FW software (default 1500), is higher than the MTU of the upstream link, it can result in packets being fragmented, lost, or otherwise mishandled. Setting MSS clamping on the WANs or changing the MTU of the interface may help.
VPN + MTU Issues
Similar to the above, if large packets or high-throughput seems to break over a VPN, enable MSS Clamping for VPN Networks under VPN > IPsec, Advanced Settings tab. The default value for the option is 1400, but try lower values such as 1350, 1300, 1250, etc.
Imported from the AZTCOFW knowledge base on 2026-09-05. Historical guidance may refer to older software versions. Confirm applicability before changing a production system.
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