subnetting
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Posted by mmark751969 on July 21, 2008, 2:25 pm
Please log in for more thread options at access layer and a 6509 at the core. We are talking about subnetting the network. 8 different subnets have been proposed. I agree that vlan subnetting has it's advantages(i.e reducing broadcast domains). But i am wondering at what point it's too much. Or what is the drawback of having too many subnets and would 8 be considered that on a 400 node network. Thanks | |||||||||||||||||||||||||
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Posted by Trendkill on July 21, 2008, 2:47 pm
Please log in for more thread options > the drawback of having too many subnets and would 8 be considered that
> on a 400 node network. =A0Thanks It all depends on the nature of the traffic. If these are all user stations, I have seen many times where a /22 is used (1000+ addresses), and 4-500 are active during regular usage. If its a mixed use vlan with real-time traffic (such as video or voice, which would not be good architecture anyway), then subnetting to smaller subnets makes more sense. In short, 8 segments for 50 nodes each is overkill. I would personally not do smaller than /25, and /24 in most cases, unless of course the network is a retail or small site network which will never get larger than that space, or there are special vlan or traffic requirements. When you are talking modern gig speed networks, broadcast traffic is minimal unless you have an issue (ie bad worm or virus), or a network design problem. | |||||||||||||||||||||||||
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Posted by Thrill5 on July 21, 2008, 5:28 pm
Please log in for more thread options There is no drawback to having too many subnets when routing with a 6500!!!!
Layer 2 switching is not any faster than layer 3 switching and smaller subnets means a smaller broadcast domain. If you are running windows, than smaller broadcast domains are good because windows workstations send out quite a bit of broadcast traffic. I never ever, ever use subnets bigger than a /24, and most subnets usually have an average of only about 60 workstations. On my network, each and every wiring closet has its own subnet, plus a voice subnet if it is a VoIP is being used. >> we have a 400 node network running on multple 3750 stackable switches
>> at access layer and a 6509 at the core. We are talking about >> subnetting the network. 8 different subnets have been proposed. I >> agree that vlan subnetting has it's advantages(i.e reducing broadcast >> domains). But i am wondering at what point it's too much. Or what is >> the drawback of having too many subnets and would 8 be considered that >> on a 400 node network. Thanks >
>It all depends on the nature of the traffic. If these are all user >stations, I have seen many times where a /22 is used (1000+ >addresses), and 4-500 are active during regular usage. If its a mixed >use vlan with real-time traffic (such as video or voice, which would >not be good architecture anyway), then subnetting to smaller subnets >makes more sense. In short, 8 segments for 50 nodes each is >overkill. I would personally not do smaller than /25, and /24 in most >cases, unless of course the network is a retail or small site network >which will never get larger than that space, or there are special vlan >or traffic requirements. When you are talking modern gig speed >networks, broadcast traffic is minimal unless you have an issue (ie >bad worm or virus), or a network design problem. The speed of the interface has nothing to do with the amount of broadcast traffic, that is a function of the number of devices in the broadcast domain. Each and every broadcast packet is sent to, and processed by, every device in the broadcast domain. | |||||||||||||||||||||||||
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Posted by Trendkill on July 21, 2008, 5:53 pm
Please log in for more thread options > There is no drawback to having too many subnets when routing with a 6500!=
!!!
> Layer 2 switching is not any faster than layer 3 switching and smaller
than
> subnets means a smaller broadcast domain. =A0If you are running windows, = > smaller broadcast domains are good because windows workstations send out
y
> quite a bit of broadcast traffic. > > I never ever, ever use subnets bigger than a /24, and most subnets usuall= > have an average of only about 60 workstations. =A0On my network, each and
IP
> every wiring closet has its own subnet, plus a voice subnet if it is a Vo= > is being used.
.
> > > > >> we have a 400 node network running on multple 3750 stackable switches
> >> at access layer and a 6509 at the core. We are talking about > >> subnetting the network. 8 different subnets have been proposed. I > >> agree that vlan subnetting has it's advantages(i.e reducing broadcast > >> domains). But i am wondering at what point it's too much. Or what is > >> the drawback of having too many subnets and would 8 be considered that > >> on a 400 node network. Thanks >
> >It all depends on the nature of the traffic. =A0If these are all user
> >stations, I have seen many times where a /22 is used (1000+ > >addresses), and 4-500 are active during regular usage. =A0If its a mixed > >use vlan with real-time traffic (such as video or voice, which would > >not be good architecture anyway), then subnetting to smaller subnets > >makes more sense. =A0In short, 8 segments for 50 nodes each is > >overkill. =A0I would personally not do smaller than /25, and /24 in most > >cases, unless of course the network is a retail or small site network > >which will never get larger than that space, or there are special vlan > >or traffic requirements. =A0When you are talking modern gig speed > >networks, broadcast traffic is minimal unless you have an issue (ie > >bad worm or virus), or a network design problem. >
every
> The speed of the interface has nothing to do with the amount of broadcast > traffic, that is a function of the number of devices in the broadcast > domain. =A0Each and every broadcast packet is sent to, and processed by, = > device in the broadcast domain.
I agree, but in the days of 10/half interfaces, broadcast could easily overwhelm a link or subnet. Today, it would take one hell of a broadcast storm to overwhelm a modern backbone or LAN link. While I don't disagree with your subnet solution (can't really go wrong here, and have to design to your requirements), my experience is in two global Fortune 50 companies, and when you have dozens of datacenters, subnetting like that adds up quick on wasted addresses. That being said, I would not go larger than a /22. And, always subnet real time traffic if possible, particularly VoIP since the requirements/ segmentation work nicely. | |||||||||||||||||||||||||
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Posted by Trendkill on July 21, 2008, 5:55 pm
Please log in for more thread options > There is no drawback to having too many subnets when routing with a 6500!=
!!!
> Layer 2 switching is not any faster than layer 3 switching and smaller
than
> subnets means a smaller broadcast domain. =A0If you are running windows, = > smaller broadcast domains are good because windows workstations send out
y
> quite a bit of broadcast traffic. > > I never ever, ever use subnets bigger than a /24, and most subnets usuall= > have an average of only about 60 workstations. =A0On my network, each and
IP
> every wiring closet has its own subnet, plus a voice subnet if it is a Vo= > is being used.
.
> > > > >> we have a 400 node network running on multple 3750 stackable switches
> >> at access layer and a 6509 at the core. We are talking about > >> subnetting the network. 8 different subnets have been proposed. I > >> agree that vlan subnetting has it's advantages(i.e reducing broadcast > >> domains). But i am wondering at what point it's too much. Or what is > >> the drawback of having too many subnets and would 8 be considered that > >> on a 400 node network. Thanks >
> >It all depends on the nature of the traffic. =A0If these are all user
> >stations, I have seen many times where a /22 is used (1000+ > >addresses), and 4-500 are active during regular usage. =A0If its a mixed > >use vlan with real-time traffic (such as video or voice, which would > >not be good architecture anyway), then subnetting to smaller subnets > >makes more sense. =A0In short, 8 segments for 50 nodes each is > >overkill. =A0I would personally not do smaller than /25, and /24 in most > >cases, unless of course the network is a retail or small site network > >which will never get larger than that space, or there are special vlan > >or traffic requirements. =A0When you are talking modern gig speed > >networks, broadcast traffic is minimal unless you have an issue (ie > >bad worm or virus), or a network design problem. >
every
> The speed of the interface has nothing to do with the amount of broadcast > traffic, that is a function of the number of devices in the broadcast > domain. =A0Each and every broadcast packet is sent to, and processed by, = > device in the broadcast domain.
I should also qualify that this entire discussion assumes centralized layer 2, which in itself is becoming a legacy design for very large networks. Distributed layer 3 is not necessarily cheap, but is feasible in most l3 switches today, and can help alleviate backbone traffic, broadcast traffic, and inter vlan routing since subnets are local to switch pairs only. | |||||||||||||||||||||||||
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> at access layer and a 6509 at the core. =A0We are talking about
> subnetting the network. =A08 different subnets have been proposed. =A0I
> agree that vlan subnetting has it's advantages(i.e reducing broadcast
> domains). =A0But i am wondering at what point it's too much. =A0Or what i=