lan-to-lan VPN bandwith decrease

Forums Network Management ZeroShell lan-to-lan VPN bandwith decrease

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    I’m using Zeroshell as an alternative to normal routers/gateways/firewalls in a university project and I have to say that I’m delighted with it. I found it to be a great piece of software and much more flexible than any other solution using expensive routers.

    My question is about bandwidth loss when using a lan-to-lan VPN.
    I have two PCs (PIII 1000MHZ, 512 MB RAM) with several NICs each acting as gateways of two different sites. Both machines are connected via 100 Mbps Ethernet and I can get an effective bandwidth of 96 Mbps. After that I created a lan-to-lan UDP VPN to connect both PC (through the same ethernet link) and tested for max bandwidth with the following results:

    Without VPN

    96 Mbps
    Encrypted and compressed VPN

    41 Mbps
    Encrypted VPN (no compression)

    34 Mbps
    VPN (no compression nor encryption)— 47 Mbps

    Are those values acceptable? I didn’t thought that I would notice such a big loss of bandwidth when tunneling the traffic through the VPN.

    The CPU usage didn’t went beyond 50% during any of the bandwidth stress tests so I assume that the problem is not related to the machines. All my NICs are 10/100 3Com branded and seem to be working OK.

    Thanks in advance for any comment/suggestion.

    Keep up the great work Fulvio and friends!



    still wondering why this is happening… any ideias!?


    I have the same problem with vpn agregation.
    I have 2 connections of 100mb but when activating the VPN, the max speed are 40 mb

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