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Wired Networks Thread, Size of VLANS in Technical; Originally Posted by CyberNerd I actually find it easier to admin - the reason being is that it is far ...
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    SYNACK's Avatar
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    Quote Originally Posted by CyberNerd View Post
    I actually find it easier to admin - the reason being is that it is far easier to diagnose a problem with/in a discrete network than one where traffic is going through multiple switches. We've got a MERU setup, and wireless clients don't even notice the difference if they go between different AP's
    Why stop there then, multiple links between multiple points BGP and/or IS-IS would probably allow for better link utilisation in that format. I can see how this could be more effective if lots of your traffic stays within the cabinet, being cloud based I'd imagine that most of your traffic would be going via the core to the net. Given the overhead of the routing protocols it may work out even. Separate subnets are easier to diagnose we just put them in different places.

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    nicholab's Avatar
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    I once got told of that I had broken my network into too many subnets by a network consultant and that one subnet was fine for 600-800 machines. I did get the hp 4108gl running out of steam for routing.

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    I use /24's for the bulk of my areas and /25's for the ones that are 'small' (less than 30 devices). Management is split into smaller subnets /25 and /26 and the guest network is a /22

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    Quote Originally Posted by CyberNerd View Post
    I actually find it easier to admin - the reason being is that it is far easier to diagnose a problem with/in a discrete network than one where traffic is going through multiple switches. We've got a MERU setup, and wireless clients don't even notice the difference if they go between different AP's
    To be fair its very rare we have a problem on the network, when we have i wouldn't of said the layer 3 to the edge helped us narrow down the problem but thats purely down to the nature of the problems we had.

    I agree any wireless system that tunnels traffic through a controller will work fine on a layer 3 network as your basically creating a virtual layer 2 network for wireless traffic, but you do take a performance hit.

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    Quote Originally Posted by nicholab View Post
    I once got told of that I had broken my network into too many subnets by a network consultant and that one subnet was fine for 600-800 machines. I did get the hp 4108gl running out of steam for routing.
    Depends on the implementation and what you are trying to achieve, if your system has robust enough routing with large route/switch mapping table and layer 3/4 bridging meaning it only has to route once then it handles it just like switch traffic bridging it. It cuts down CPU use and removes the penalties in speed as it is just as quick as local switching but with all the benefits of routing. This is what I was talking about with regard to solid layer 3 switching earlier.

    There is too much but it depends on your situation. If you are dealing with every user being an active threat then a subnet per user is not excessive but almost no one is in that situation. As with everything it all depends on the situation. Some of this may change with IPv6 too.
    Last edited by SYNACK; 5th April 2013 at 12:40 AM.

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    I manage seven buildings interconnected with private fiber at 1GB link speed with a Cisco 6506 at the core. Most of my subnets are /23 and each building handles about five or six VLANs. There certainly isn't 510 wired devices in each elementary, but we purposely doubled the subnet size so we could split it across two DHCP servers. Have one server hand out addresses for the bottom part of the sub, the second for the top half. The only problem I've had with broadcast traffic was with some phone equipment and LAN School when it was looking for clients. The solution was to make a flat /24 VLAN across the entire district and place the phone equipment on it.

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    It's actually fairly standard design, and you don't need an L3 switch in every cabinet. The L2 vlan only has to be present on the switch - it doesn't get assigned to any ports, just tagged across your trunks and pruned where necessary.

    Does that mean the vlan extends past the local switch? Technically perhaps, but the point being you have eliminated the broadcast issue which is the point.

    If you have L3 switches, great, use them, I'd say there's no point in buying L2 only switches these days anyway, the additional cost is minimal.

    Hell, HP is offering buy 2 get 1 free on their 2900 switches.

    Your L3 gateway can still be at your distribution layer - where it should be, not at your core, unless you are a smaller environment running a collapsed core in which case go right ahead.

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    Quote Originally Posted by apeman View Post
    I must say this setup is a pain in the A*se to admin and wireless clients hate it as they are constantly roaming and changing IP.
    I'd make this the exception. Your APs are switches, treat them as such and connect via trunks using their own subnet (per SSID). That subnet doesn't change and exists as a L2 vlan on any switch connected to an AP. No access ports using this vlan, so broadcast isn't an issue and your AP's should limit client broadcasts anyway if it's decent gear.

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    Quote Originally Posted by Destinova View Post
    Does that mean the vlan extends past the local switch? Technically perhaps, but the point being you have eliminated the broadcast issue which is the point..
    Yes that means it does extend past the local switch and that is the point, it is how many networks are setup and that is fine.

    Quote Originally Posted by Destinova View Post
    If you have L3 switches, great, use them, I'd say there's no point in buying L2 only switches these days anyway, the additional cost is minimal.

    Hell, HP is offering buy 2 get 1 free on their 2900 switches.
    Maybe in Canada but we get ripped apart on pricing so it can easily be double and the low end l3 stuff is not really worth having anyway. It would be nice to be given effecivly free hardware but the corporate overloards deam us to be a market that they wring every last drop of cash out of so they can afford a few more olympic sized pools for their homes.

    Quote Originally Posted by Destinova View Post

    Your L3 gateway can still be at your distribution layer - where it should be, not at your core, unless you are a smaller environment running a collapsed core in which case go right ahead.
    Indeed, colapsed core is fine and the right solution for smaller networks, we only have about 400-500 clients so the three layer design is not nessisary.

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    Quote Originally Posted by SYNACK View Post
    Yes that means it does extend past the local switch and that is the point, it is how many networks are setup and that is fine.



    Maybe in Canada but we get ripped apart on pricing so it can easily be double and the low end l3 stuff is not really worth having anyway. It would be nice to be given effecivly free hardware but the corporate overloards deam us to be a market that they wring every last drop of cash out of so they can afford a few more olympic sized pools for their homes.



    Indeed, colapsed core is fine and the right solution for smaller networks, we only have about 400-500 clients so the three layer design is not nessisary.
    Only the L2 vlan extends past the local switch. This is fine. Design and security suggests you want to avoid broadcast - this does that.

    If HP is ripping you off in the UK then look to Cisco. First, their gear is superior and their warranty now matches HP's completely. The only hope HP has ever had in the networking space has been on price, and if they aren't doing that for you, tell them to stuff it.

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    Quote Originally Posted by Destinova View Post
    Only the L2 vlan extends past the local switch. This is fine. Design and security suggests you want to avoid broadcast - this does that.

    If HP is ripping you off in the UK then look to Cisco. First, their gear is superior and their warranty now matches HP's completely. The only hope HP has ever had in the networking space has been on price, and if they aren't doing that for you, tell them to stuff it.
    Not UK, New Zealand, we easily pay double or more what the UK does for networking gear and the UK lot still get ripped of in comparison to the US. Cisco stuff is new car level of prices for the lowest mid level switches under educational pricing.

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    Quote Originally Posted by SYNACK View Post
    Not UK, New Zealand, we easily pay double or more what the UK does for networking gear and the UK lot still get ripped of in comparison to the US. Cisco stuff is new car level of prices for the lowest mid level switches under educational pricing.
    That's interesting. The Cisco EDU discount here (Canada) is fairly close to 40% off list price, depending on what gear you're looking at. Comparison on the Cisco/HP side (I sell both as a consultant) Cisco can get very close to HP pricing, but can't offer the 2-for-1 or 3-for-2 deals that they often have on their lower end L2 and L3 switches, which is usually the tipping point for anyone buying bulk.

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    Quote Originally Posted by CyberNerd View Post
    Most of the decent switches are L3 anyway, and it does make a good deal of sense. Some would even argue that the uplinks should be OSPF VLAN's of their own (ie a vlan of 2). There isn't any point in polluting uplinks with random traffic that doesn't need to be there. I've got 4 links like this and it works pretty well.
    This is our approach. It works well but does require a lot of investment, time as well as money, to set up. We've used this approach to connect each edge and each core together with redundant routes.

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    Quote Originally Posted by Roberto View Post
    This is our approach. It works well but does require a lot of investment, time as well as money, to set up. We've used this approach to connect each edge and each core together with redundant routes.
    You can do that with STP also and get rid of the protocol overhead but as always the best solution depends on the requirements.

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    The easiest way is to start with addressing the network, making sure you have the right number of hosts that you require on each network or vLAN. Once you have done this you can then look at summarsing the network at the relevant boundaries. If you have some transit networks between two devices use /30's

    If I can be of any help drop me a PM, happy to run stuff through ;-)

    Cheers



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