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I have a single uplink with my ISP at a data center. I have 2 routers (CISCO 3850). How do I connect these routers to that uplink WITHOUT a network switch? That switch will be a single point of failure.

Is there something like ATS for ethernet. I mean one ethernet IN port and two OUT ports and this device route packets to primary OUT port if it is active (if there is a link) and route to the secondary if it is not active. Will be even better if it is passive device.

I don't mind to use a network switch between the routers and uplink but it has to be like 10 times more reliable that normal switches. Is there such thing as super reliable network switch where everything is redundant? I do know that such network switches with dual CPU card, dual power supplies, line card exist but they are huge and pricey. Are there cheaper fully redundant switches ?

Is there another solution ?

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  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin ♦
    Commented Apr 1, 2018 at 22:52
  • Thank Ron Maupin for helping me but I would like to keep it open.
    – Igor Chulkov
    Commented Apr 4, 2018 at 2:56

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I have a single uplink with my ISP at a data center. I have 2 routers (CISCO 3850). How do I connect these routers to that uplink WITHOUT a network switch? That switch will be a single point of failure.

No. You are going to have a SPoF no matter what you do with a single ISP link. A switch, hub, your ATS idea, etc. all represent a SPoF, as is the single link and single ISP device to which the link connects.

Even with the big, pricey, multi-supervisor switch, you will be at the mercy of a line card, or even a port on the line card. In fact, we have found that your standard business-grade equipment is much more reliable than the data circuit to which we connect the equipment. If you want to eliminate the SPoF, you need dual circuits from different ISPs in different physical paths to the site.

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  • I do understand, but that uplink is a passive cable at a data center and I don't worry about it too much. Not all network switches are the same. I would chose a newtwork switch that is 10 times more reliable than a normal switch. I guess you can make a very reliable switch by making it simpler and using better components, everything redundant. Does somebody know such switches ?
    – Igor Chulkov
    Commented Mar 20, 2018 at 3:40
  • Why don't you have two switches set up, then move from one to the other? It may be cheaper to have two of those than a large switch for three connections. One ethernet cable only has two ends, so there will be a single device on each end, and each of those devices is a SPoF.
    – Ron Maupin ♦
    Commented Mar 20, 2018 at 3:44
  • @IgorChulkov, product or resource recommendations are explicitly off-topic for SE sites, except Software Recommendations and Hardware Recommendations.
    – Ron Maupin ♦
    Commented Mar 20, 2018 at 3:45
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    The uplink is not the passive cable at a datacenter. It is the switch on the other end of that passive cable, and that switch is quite active and quite complex. If you are at a datacenter, you should be able to get two cables to redundant switches and use VRRP.
    – Slartibartfast
    Commented Mar 20, 2018 at 3:46
  • I didn't know that but at least if somebody can recommend class of such devices or type of such devices for examle class 10, or class A or whatever.
    – Igor Chulkov
    Commented Mar 20, 2018 at 3:47
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As mentioned by Ron, a quality network switch is going to be more reliable than you think. However, there might be another option for, depending on your circumstances. At most colocation data centers, you can get your internet circuit delivered on a second cable for a small up-charge. It's not a second circuit, rather a second cable for the first circuit. The provider normally have two core devices, so each cable will come off of a different core. You plug each cable into its own switch, and plug those two switches together. Those would be unprotected switches, so lock them down good! Then, your two Cisco 3850 devices (which are actually switches, aren't they?, unless you mean 3851 routers?) each plug into one of your switches. If you combine that with HSRP, you should have the redundancy that you're asking for.

A redundant internet solution

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  • Thanks user3629081. I understand how to make it work with 2 uplinks. I need to make it redundant with 1 uplink. Disregard ISPs router and uplink's reliability.
    – Igor Chulkov
    Commented Apr 4, 2018 at 3:00
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    Good, cheap, fast -- pick two. Your desired scenario does not exist.
    – user3629081
    Commented Apr 4, 2018 at 12:59
  • My scenario would be possible if that Enternet ATS existed. I don't understand why nobody produces it.
    – Igor Chulkov
    Commented Apr 11, 2018 at 3:22
  • @IgorChulkov A passive Ethernet ATS does not exist because there mandatorily must be intelligence inside the device to determine whether the carrier signal of Ethernet is present or not. (It's not like a electrical ATS that just sees voltage.) That intelligence then introduces new electronics and software that can fail, thus canceling out any added benefit of the ATS. This type of ATS could be created, but nobody would buy it, therefore it is not created, manufactured, distributed, and sold at stores.
    – user3629081
    Commented Apr 11, 2018 at 16:50
  • I would totally buy it. You can make it really simple. A couple or relays that mechanically route from one port to another. If it has 100 times less components than a network switch then it will be MUCH more reliable. You can even use military grade components. I would totally buy it even for 1000 bucks. It should exist for the same reason ATS switch exist. They are very simple devices and don't fail that often as network switches. If I wasn't so lazy I would probably design/order such devices and start selling.
    – Igor Chulkov
    Commented Apr 13, 2018 at 1:26

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