VLAN confusion
-
@dave247 said in VLAN confusion:
@dashrender said in VLAN confusion:
@jaredbusch said in VLAN confusion:
Then you change your few static devices (if you do not have only a few static systems, you have other issues).
What JB means by this is - he uses static assignments in DHCP for things like printers. This allows you to reboot a printer to get the new settings when things like this change.
Servers are about the only thing that should be set statically, the rest can rely on Static DHCP assignment.
oh man.. the printers.. I forgot about all the statically assigned printers we have. My company has about 30 statically assigned printers. That will be a huge pain in the butt to change..
Move them to DHCP while you do it. two bird, one stone.
But remember, if the things in the new range don't need to print, no need to change them.
-
@dave247 said in VLAN confusion:
Stepping back in the discussion a bit.. I didn't understand your reply here. Isn't it best-practice to have a single network on a VLAN?
Absolutely not. VLANs are for security and management, only. Period. No other purpose for them. No best practice adds VLANs to other concerns. VLANs are widely used, because security and management needs create cause for them. But those are the singular reasons for which VLANs are sensible.
-
@dave247 said in VLAN confusion:
Like, if I had a company network of 200 systems on one network and a LAB network of 20 systems, I wouldn't want them sharing the same switch/VLAN, would I?
You lept topics. You asked about subnetting, now you are asking about security. Like I keep saying, if you are VLANing for security, then you use VLANs. And VLANs imply "same switch."
The issue in your example is that you need the VLAN to keep them apart, but you don't need separate subnets. You likely want separate subnets, but not for security reasons, just for convenience since the VLANs will be a pain without it. But the subnet exists solely to support the VLAN, not the other way around.
-
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
Stepping back in the discussion a bit.. I didn't understand your reply here. Isn't it best-practice to have a single network on a VLAN?
Absolutely not. VLANs are for security and management, only. Period. No other purpose for them. No best practice adds VLANs to other concerns. VLANs are widely used, because security and management needs create cause for them. But those are the singular reasons for which VLANs are sensible.
Sorry, let me change the term "VLAN" to "switch". Is it best practice to avoid having multiple networks running on a single switch? I just said VLAN because of the default VLAN..
-
@dave247 said in VLAN confusion:
Sorry, let me change the term "VLAN" to "switch". Is it best practice to avoid having multiple networks running on a single switch? I just said VLAN because of the default VLAN..
The entire concepts of subnetting and VLANing are to run multiple networks on a single switch
Nothing wrong with that in the least. Switches are expected to run multiple networks, that's just normal and exactly what they are meant to do. -
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
Sorry, let me change the term "VLAN" to "switch". Is it best practice to avoid having multiple networks running on a single switch? I just said VLAN because of the default VLAN..
The entire concepts of subnetting and VLANing are to run multiple networks on a single switch
Nothing wrong with that in the least. Switches are expected to run multiple networks, that's just normal and exactly what they are meant to do.So if I had 20 different /24 networks running on the same switch stack (for whatever reason), and all of them are on VLAN 0 (I'm just saying VLAN here because everything will at least be on the default VLAN), then there will be no traffic issues whatsoever?
-
@dave247 said in VLAN confusion:
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
Sorry, let me change the term "VLAN" to "switch". Is it best practice to avoid having multiple networks running on a single switch? I just said VLAN because of the default VLAN..
The entire concepts of subnetting and VLANing are to run multiple networks on a single switch
Nothing wrong with that in the least. Switches are expected to run multiple networks, that's just normal and exactly what they are meant to do.So if I had 20 different /24 networks running on the same switch stack (for whatever reason), and all of them are on VLAN 0 (I'm just saying VLAN here because everything will at least be on the default VLAN), then there will be no traffic issues whatsoever?
No, no issues, not from traffic. Things like DHCP wouldn't work, obviously.
-
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
Sorry, let me change the term "VLAN" to "switch". Is it best practice to avoid having multiple networks running on a single switch? I just said VLAN because of the default VLAN..
The entire concepts of subnetting and VLANing are to run multiple networks on a single switch
Nothing wrong with that in the least. Switches are expected to run multiple networks, that's just normal and exactly what they are meant to do.So if I had 20 different /24 networks running on the same switch stack (for whatever reason), and all of them are on VLAN 0 (I'm just saying VLAN here because everything will at least be on the default VLAN), then there will be no traffic issues whatsoever?
No, no issues, not from traffic. Things like DHCP wouldn't work, obviously.
MY MIND IS BLOWN
-
Let's step back and work on this concept of "traffic issues." What is a "traffic issue" to you and where do you think that it comes from?
-
@dave247 said in VLAN confusion:
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
Sorry, let me change the term "VLAN" to "switch". Is it best practice to avoid having multiple networks running on a single switch? I just said VLAN because of the default VLAN..
The entire concepts of subnetting and VLANing are to run multiple networks on a single switch
Nothing wrong with that in the least. Switches are expected to run multiple networks, that's just normal and exactly what they are meant to do.So if I had 20 different /24 networks running on the same switch stack (for whatever reason), and all of them are on VLAN 0 (I'm just saying VLAN here because everything will at least be on the default VLAN), then there will be no traffic issues whatsoever?
No, no issues, not from traffic. Things like DHCP wouldn't work, obviously.
MY MIND IS BLOWN
LOL, I get the impression that somewhere in your thinking on switches, you are associating them with hubs or something. The concerns that you have sound like something we'd have worried about in the 1990s. But you aren't that old to have learned networking prior to 2000, are you?
-
@scottalanmiller said in VLAN confusion:
Let's step back and work on this concept of "traffic issues." What is a "traffic issue" to you and where do you think that it comes from?
Not to keep back-peddling.. but maybe I should have just said "issues". Maybe not even that. I'm just asking about best practice here. Simply: is it supposed to be one network per switch? But you answered no. I'm not sure where I got my assumptions, but at least I'm trying to work out my understanding of these concepts here..
-
Think of a switch like a big open parking lot. You can enter from dozesn or different locations and exit at any of dozens of locations. You are a packet, obviously. The parking lot is huge and there is enough room for everyone to get to where they need to go. Each connection is unique, from point to point, the only points of congestion come at the driveway, if a single driveway wants to send out too many cars at once or take too many in.
A simple switch, like a 24 port GigE switch, will often have a 40Gb/s backplane. That means that even if every port on the switch is at full capacity, it can't saturate the backplane. There is no capacity advantage by splitting up the traffic further, the switch is already handling it all at full speed. The ports are the bottlenecks, not the switch.
-
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
@scottalanmiller said in VLAN confusion:
@dave247 said in VLAN confusion:
Sorry, let me change the term "VLAN" to "switch". Is it best practice to avoid having multiple networks running on a single switch? I just said VLAN because of the default VLAN..
The entire concepts of subnetting and VLANing are to run multiple networks on a single switch
Nothing wrong with that in the least. Switches are expected to run multiple networks, that's just normal and exactly what they are meant to do.So if I had 20 different /24 networks running on the same switch stack (for whatever reason), and all of them are on VLAN 0 (I'm just saying VLAN here because everything will at least be on the default VLAN), then there will be no traffic issues whatsoever?
No, no issues, not from traffic. Things like DHCP wouldn't work, obviously.
MY MIND IS BLOWN
LOL, I get the impression that somewhere in your thinking on switches, you are associating them with hubs or something. The concerns that you have sound like something we'd have worried about in the 1990s. But you aren't that old to have learned networking prior to 2000, are you?
I'm 34. I started college in 2002, probably around the time hubs were almost completely dead. I did order a few on ebay and then I got a free "smart hub" that I didn't really do too much with aside.. I had a few classes on networking but nothing too deep and my ability to study and learn used to be pretty terrible, so yes, I probably started building my understanding around hubs and classful networking.
At least I do fully understand classless subnetting now though.. I just need to iron out the rest of the kinks in how I understand this stuff.
-
@dave247 said in VLAN confusion:
I'm 34. I started college in 2002, probably around the time hubs were almost completely dead
Yeah, even my home was fully switched by that point.
-
For your own learning, try working backwards. Where in a switch do you perceive bottlenecks or performances issues? See if you can figure out what you are picturing, maybe there is a misconception that we can address.
-
@scottalanmiller said in VLAN confusion:
Think of a switch like a big open parking lot. You can enter from dozesn or different locations and exit at any of dozens of locations. You are a packet, obviously. The parking lot is huge and there is enough room for everyone to get to where they need to go. Each connection is unique, from point to point, the only points of congestion come at the driveway, if a single driveway wants to send out too many cars at once or take too many in.
A simple switch, like a 24 port GigE switch, will often have a 40Gb/s backplane. That means that even if every port on the switch is at full capacity, it can't saturate the backplane. There is no capacity advantage by splitting up the traffic further, the switch is already handling it all at full speed. The ports are the bottlenecks, not the switch.
Good analogy, and I think I've gotten this concept more fully as of late. One of the terms I hadn't heard of before starting my job was the "backplane" word. I'm still not 100% certain on what it means, but I assume it's just the connecting board that all circuits pass through.. like a backbone or something.
-
@dave247 said in VLAN confusion:
@scottalanmiller said in VLAN confusion:
Think of a switch like a big open parking lot. You can enter from dozesn or different locations and exit at any of dozens of locations. You are a packet, obviously. The parking lot is huge and there is enough room for everyone to get to where they need to go. Each connection is unique, from point to point, the only points of congestion come at the driveway, if a single driveway wants to send out too many cars at once or take too many in.
A simple switch, like a 24 port GigE switch, will often have a 40Gb/s backplane. That means that even if every port on the switch is at full capacity, it can't saturate the backplane. There is no capacity advantage by splitting up the traffic further, the switch is already handling it all at full speed. The ports are the bottlenecks, not the switch.
Good analogy, and I think I've gotten this concept more fully as of late. One of the terms I hadn't heard of before starting my job was the "backplane" word. I'm still not 100% certain on what it means, but I assume it's just the connecting board that all circuits pass through.. like a backbone or something.
In the case of a switch, the backplane is actually a bus, but one with a lot of logic associated with it. It's so fast, that generally it is faster than the cumulated speed of all things that connect to it. Not always, but always so fast that you generally don't care. It's like a super highway of thousands of lanes, but only a quarter mile long
So insane bandwidth, no latency.Every packet that goes into or out of the switch travels between the ports via the backplane. It's what connects the whole thing together.
-
@scottalanmiller said in VLAN confusion:
For your own learning, try working backwards. Where in a switch do you perceive bottlenecks or performances issues? See if you can figure out what you are picturing, maybe there is a misconception that we can address.
Well at this point, I see the potential bottlenecks being at the points where our switches connect to each other. We currently have six layer 3 Dell PowerConnect switches that all connect to each other via Link Aggregation/portshield groups. At the "center", we have all our servers and computers in our main building that connect to a stack of switches (stacked with mini-SAS) and then on that stack, there are a couple of LAG groups consisting of 3 ports each that run off to four different closets. Actually, one of them is our basement, which ... you know, screw it. I'm uploading a diagram I just did in MS Paint so you can see our layout. I'm aware that there are issues with the design:
-
@dave247 said in VLAN confusion:
Well at this point, I see the potential bottlenecks being at the points where our switches connect to each other.
Those are called the ports and are what I mentioned. But the issue there is outside of the switch, not inside it. This is exactly why you want to avoid VLANs, because VLANs make you use those bottlenecks more often.
-
So in that diagram, the bottlenecks would remain even if you segmented by network addressing. As long as the data needs to get from the core to the edge over the same LAG group, the bottleneck remains identical, regardless of the number or segmentation of the switches out at the edge.
