HP Switches 2530 vs 1950 vs 1920
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@Dashrender said:
I have 5 switches total. VLANing because I was old school when I set it up originally not liking the idea of collision domains greater than 256 devices - frankly still don't but I trust the math that with switches having a /31 or /30 network shouldn't be an issue. But changing it would require redoing the IP scheme across the board.
Switches don't have collision domains, by definition. You are thinking of hubs circa 1999.
Switches can have /22 no problem. Normal people have /24.
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/24 is 256 devices, /23 is 512, /22 is 1024.
Really /21 is fine these days. Even on Wall St. /22 is common.
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@scottalanmiller said:
@Dashrender said:
I have 5 switches total. VLANing because I was old school when I set it up originally not liking the idea of collision domains greater than 256 devices - frankly still don't but I trust the math that with switches having a /31 or /30 network shouldn't be an issue. But changing it would require redoing the IP scheme across the board.
Switches don't have collision domains, by definition. You are thinking of hubs circa 1999.
Switches can have /22 no problem. Normal people have /24.
You're right - I'm completely beside myself today and wrote the wrong number. I have /24 today, I'd have to go to /23 (or /22 - to never worry again) to get all of my devices inside a single network.
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@scottalanmiller said:
/24 is 256 devices, /23 is 512, /22 is 1024.
Really /21 is fine these days. Even on Wall St. /22 is common.
Yeah - I wasn't thinking... we have /30 from some of our ISPs... and I was just confusing them... of course /24 is the common.
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@Dashrender said:
You're right - I'm completely beside myself today and wrote the wrong number. I have /24 today, I'd have to go to /23 (or /22 - to never worry again) to get all of my devices inside a single network.
That would be what to do. The most demanding networks work fine on /22. Since there is no such thing as collisions, any issue with a /22 or even a /21 means you have something wrong on the network already.
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I agree there aren't collisions anymore (at least with switches) but what do you call the domain that all broadcasts go to? You could still have saturation cause by broadcasts storms, but those are normally limited to a single VLAN - though I'm guessing the pegging out of the processor on the switch is the main concern, so it doesn't really matter if all of the VLANs run through the switch, they'll all be affected.
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@Dashrender said:
I agree there aren't collisions anymore (at least with switches) but what do you call the domain that all broadcasts go to?
A broadcast domain. Broadcasts cross bridges, collisions do not.
If you have any concerns with broadcasts on /22 it means you have something wrong that you need to address. Being on /24 would be a bandaid, not a fix.
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@scottalanmiller said:
@Dashrender said:
I agree there aren't collisions anymore (at least with switches) but what do you call the domain that all broadcasts go to?
A broadcast domain. Broadcasts cross bridges, collisions do not.
If you have any concerns with broadcasts on /22 it means you have something wrong that you need to address. Being on /24 would be a bandaid, not a fix.
yeah I came to that conclusion while writing the previous post.
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@Dashrender said:
You could still have saturation cause by broadcasts storms, but those are normally limited to a single VLAN
You can have that with a /28. IF this is happening at any of these sizes it is because something is terribly wrong. If you are going to /24 because of this you are not addressing what is actually wrong on the network.
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@Dashrender said:
though I'm guessing the pegging out of the processor on the switch is the main concern, so it doesn't really matter if all of the VLANs run through the switch, they'll all be affected.
That's possible. VLANs will limit some things in the case where there is a disaster. But yes, if it pushes the switch hard or bottlenecks any of the ports, you are screwed.
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@scottalanmiller said:
That would be what to do. The most demanding networks work fine on /22. Since there is no such thing as collisions, any issue with a /22 or even a /21 means you have something wrong on the network already.
Where is a good document proving that though?
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This is why I recommend a single big flat network with a single switching infrastructure. Gets rid of the bottlenecks.
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@JaredBusch said:
Where is a good document proving that though?
That 256 is a problem? I'm not aware of there being anything to suggest that it is.
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@scottalanmiller said:
This is why I recommend a single big flat network with a single switching infrastructure. Gets rid of the bottlenecks.
I recommend OBFN because I never know who may follow behind me, and VLAN setup is NOT simple for many in the SMB market.
But that reasoning has nothing to do with actual functionality and broadcast domain max sizes.
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From the certification days, the use of the /24 was because of collisions primarily and because of the Classing, not because of size issues with broadcast domains. Which is why all the enterprises that I've seen moved to bigger networks once they went to switches.
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@JaredBusch said:
@scottalanmiller said:
This is why I recommend a single big flat network with a single switching infrastructure. Gets rid of the bottlenecks.
I recommend OBFN because I never know who may follow behind me, and VLAN setup is NOT simple for many in the SMB market.
But that reasoning has nothing to do with actual functionality and broadcast domain max sizes.
That too, easier to set up, easier to make highly performant and way easier to hand off.
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You can still do stacked switches or a single switch at this size without doing away with VLANs. But VLANs mean you need more expensive switches that have to do more processing. Technically, VLANs would necessitate L3 processing which, in turn, puts the switches at more risk of being overloaded as they are doing a lot more. But normally you overbuy L3 switches compared to L2, but latency still increases.
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Yeah all that makes sense - Damn it will be a hassle to convert... but It's probably time to consider it. Now would be better than when I move to another 50 IP phones in a few months.
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What I would recommend considering is this:
- Get a new switch designed around migrating to OBFN (stackable.)
- Slowly move IPs over time to the new IP range as you can do so easily.
- Every time you replace a switch, get another stack member and move things over.
- Profit
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@Dashrender said:
Yeah all that makes sense - Damn it will be a hassle to convert... but It's probably time to consider it. Now would be better than when I move to another 50 IP phones in a few months.
Yes, when putting in a new switch and when doing a big move would be a good time.
