Redundant Network Connections



  • Inspired by this post, and related to this one.

    At our co-location site, we have two network links in our rack, which connect to two different access switches in the data center. I suppose this is good thing, since if one the colo's switches goes down, you have a link to another switch that's active. However, like everything, the value of this "depends."

    Here is how this is currently configured. Our ASA has a VLAN (with one of our public IPs assigned to the VLAN interface), which has two ports, one going to each of the aforementioned links.

    I'm questioning the value of having these two links (and paying for the second, which from what I gather is something like $50 / month). Having dual links do not eliminate other single points of failure on the network: one ASA (soon to be ERL) connected to one switch (Dell PowerConnect 6200 series) to which all of our hosts connect. I know we'd never invest in having redundant switches and routers as it simply wouldn't make sense.

    What are you folks' thoughts on having dual-WAN connections on a single device? Does it really bring any value? I know that we don't have any kind of arrangement where we have two different ISPs servicing our rack, so both of the connections likely end up at the same ISP.



  • @eddiejennings If it were two different ISPs, maybe. Links from the same ISP are probably both originating from the same point, so not really redundant. I have done this in the past when only extremely slow speeds were available to load balance between two.

    Either way, using a single router makes the most sense. The configuration headaches and PEBKAC errors that can happen with "redundant" routers is generally a bigger headache than the downtime you'd save.



  • @travisdh1 said in Redundant Network Connections:

    @eddiejennings If it were two different ISPs, maybe. Links from the same ISP are probably both originating from the same point, so not really redundant. I have done this in the past when only extremely slow speeds were available to load balance between two.

    Either way, using a single router makes the most sense. The configuration headaches and PEBKAC errors that can happen with "redundant" routers is generally a bigger headache than the downtime you'd save.

    I agree. Keeping the two links seems like unnecessary complexity.



  • Well, ISPs TEND to fail way more often than devices. But the most common thing is to just get a second ERL. That's like $95, just configure it and stack it but don't plug it in. If the first one fails, just swap the power, and cables, and done.



  • @scottalanmiller said in Redundant Network Connections:

    Well, ISPs TEND to fail way more often than devices. But the most common thing is to just get a second ERL. That's like $95, just configure it and stack it but don't plug it in. If the first one fails, just swap the power, and cables, and done.

    yea,.. power went out in my area (350 people) which also took out the ISP local switch... pointless for me to have UPS for the network gear with the ISP down.



  • We do have dual-wan connections, but we're also connecting 3 locations together. If we only had one connection connecting all 3 locations together, and one connection died, then that location (more than likely to be a plant) will be spending the day without any productivity because they wouldn't have access to the resources that they need. We're talking 250 people working at any one time at at least $11/hr.
    11x250=$2750/hr (along with the added value they make to the company) versus $100-600/month for the extra WAN connection. It only makes sense for us to have the availability here to keep people working.



  • @scottalanmiller how do most DCs handle the IPs they hand out. Assuming your internet connection is part of your rent at the DC, then I'm guessing you don't get much say in what ISP is used. Most DCs also have multiple ISPs for their own reasons (I'm guessing redundancy mostly) - so my question is - are the IPs provided by most ISPs already ISP redundant?



  • @nerdydad said in Redundant Network Connections:

    We do have dual-wan connections, but we're also connecting 3 locations together. If we only had one connection connecting all 3 locations together, and one connection died, then that location (more than likely to be a plant) will be spending the day without any productivity because they wouldn't have access to the resources that they need. We're talking 250 people working at any one time at at least $11/hr.
    11x250=$2750/hr (along with the added value they make to the company) versus $100-600/month for the extra WAN connection. It only makes sense for us to have the availability here to keep people working.

    Yep, makes a lot of sense, especially when you have more than a single ISP available in your area (lucky!).



  • @nerdydad said in Redundant Network Connections:

    We do have dual-wan connections, but we're also connecting 3 locations together. If we only had one connection connecting all 3 locations together, and one connection died, then that location (more than likely to be a plant) will be spending the day without any productivity because they wouldn't have access to the resources that they need. We're talking 250 people working at any one time at at least $11/hr.
    11x250=$2750/hr (along with the added value they make to the company) versus $100-600/month for the extra WAN connection. It only makes sense for us to have the availability here to keep people working.

    The City (another job I had) had every offsite pointing via Dish to Cityhall just to get internet. Some were 3-4 jumps. Single point of failure for the entire City. Every electrical storm took our 25% of our dishes.