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Trouble getting multi-gig on a TZ670.

I have a TZ670. I recently purchased a SonicWall 02-SSC-1874 SFP+ 10GBase-T Transceiver Copper RJ45 Module. I live in an area where Comcast/Xfinity is the ISP. We are subscribed to a plan that is (supposedly) to provide 1200 Mbps. We have their latest and greatest modem, which is set to bridge mode.

On the SonicWall, I have X1 and X9 configured as WAN zones. I have Failover & LB enabled as a Basic Failover with X9 being priority 1 and X1 being priority 2.

When I connect the modem to X1, I receive a link status of 1 Gbps Full Duplex on the Interfaces screen. However, when I connect the same modem to the Transceiver Module plugged into X9, I get only 100 Mbps.

I ensure to power cycle to modem when I switch between X1 and X9. And tried matching the priority 1 to the current connection (not that it should make a difference in theory, but just wanted to be sure).

When I spoke to Comcast about their modem, I asked if there was a specific port on their modems I should be using to receive the full 1.2 Gbps. The Comcast technician said it should not matter which of the 4 ports you use. I should get the 1.2 Gbps on any of them. I question whether or not that is true, but at this point I have to take his word.

I would assume I should at least get the same link speed on X9 as I would on X1. How do get the multi-gig speed on X9?

Thank you for any assistance on this matter.

Category: Entry Level Firewalls


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    AjishlalAjishlal Community Legend ✭✭✭✭✭


    First make sure the comcast modem will support the multi-gig speed.

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    TKWITSTKWITS Community Legend ✭✭✭✭✭
    edited April 2022

    Check that the modem model has 10G BaseT or SFP+ ports, otherwise it's likely the modem only has 1G ports. It could be the SFP module is not auto-negotiating properly, you can try to hard set it to 1G Full.

    Sounds to me like they are selling a speed they cannot technically achieve...

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    RussFRussF Newbie ✭

    If you want my personal opinion (which is worth every penny you are paying for it), I think you were sold a bill of goods. According to Xfinity's own support website here: ,

    The cabling requirements for internet speeds up to 1200 Mbps:

    "Cat5e or Cat6 Ethernet cable.

    Note: Due to Ethernet overhead, actual download speeds are limited to 940 Mbps over a hardwired connection."

    For higher speeds:

    "For maximum speeds of 2 Gbps on a single computer, you will need the following:

    • A desktop computer with available PCIe expansion slot.
    • A 10G PCIe network interface controller (NIC) adapter with small form-factor pluggable (SFP) cage.
    • A 10G enhanced, 850nm multimode fiber (MMF), small form-factor pluggable (SFP) transceiver.
    • A multimode fiber (MMF) LC patch cable."

    Note that for higher speeds, a fiber connection is required - which leads me to believe that their RJ45 ports do NOT support anything higher than 1Gbps.

    So, according to their own documentation, with 1200 Mbps, you will never see more than 940 Mbps anyway. Besides, if your in-house cable plant only supports 1 Gbps, you will never see higher throughput to any one device, regardless of the ISP's bandwidth. To realize faster speeds, you must upgrade all of your equipment AND cabling to support 10 Gbps.

    Also, don't even THINK about realizing that kind of speed over wifi. According to , real-life expected speeds are:

    "Below is a breakdown of actual real-life average speeds you can expect from wireless routers within a reasonable distance, with low interference and small number of simultaneous clients:

    802.11b - 2-3 Mbps downstream, up to 5-6 Mbps with some vendor-specific extensions.

    802.11g - ~20 Mbps downstream

    802.11n - 40-50 Mbps typical, varying greatly depending on configuration, whether it is mixed or N-only network, the number of bonded channels, etc. Specifying a channel, and using 40MHz channels can help achieve 70-80Mbps with some newer routers. Up to 100 Mbps achievable with more expensive commercial equipment with 8x8 arrays, gigabit ports, etc.

    802.11ac - 100+ Mbps typical, higher speeds (300+ Mbps) possible over short distances without many obstacles, with newer generation 802.11ac routers, and client adapters capable of multiple streams."

    Sorry to burst your bubble - have a great day!


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