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Stacking

Discussion in 'Networks' started by simongrahamuk, Jun 23, 2007.

  1. simongrahamuk
    Honorary Member

    simongrahamuk Hmmmmmmm?

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    when looking into switches I have often seen the term "stackable" mentioned. Now it is not something that I have ever really thought about before, but can anyone actually expand on what that term means? :blink
     
  2. Boycie
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    Boycie Senior Beer Tester

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    I always thought it meant a switch that could be stacked, ie in a "U rack" opposed to the cheaper ones which have no means of being mounted to anything.

    Si
     
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  3. zebulebu

    zebulebu Terabyte Poster

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    Si

    There are probably better definitions, but the best i can think of is that stackable switches allow more than one physical switch to be clustered in such a way as to appear to be a single unit. Stackable switches have a port on their backplane which allows connection to another unit. One unit is usually defined as the 'master', and a stack can consist of as many, or as few as the management software for the switch O/S allows.

    This isn't to be confused with what some people assume stacking to be (connecting switches via uplink ports) as you don't get any of the management features you would with a 'real' stack.

    ...Cue Harry to come along and show me up with a much better definition :biggrin
     
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  4. Boycie
    Honorary Member

    Boycie Senior Beer Tester

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    oh, that too.

    No, seriously i didn't release that was what it was referring to - thanks Zeb! :)

    That's what I love about CF - it's brimming with knowledge. 8)
     
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  5. simongrahamuk
    Honorary Member

    simongrahamuk Hmmmmmmm?

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    So let me see if I can understand this right:

    I have numerous managed switches each which have their own IP allocated, if the switches were 'stackable' then I could configure a single IP for them all (or at least those in the same vacinity) and make them 'appear' as a single entity on the network?

    Any one care to expand on why I would want to do that?
     
  6. Headache

    Headache Gigabyte Poster

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  7. r.h.lee

    r.h.lee Gigabyte Poster

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    simongrahamuk,

    Let's look at the "unstackable" managed switch scenario. Let's say you are in your office in "Building 1." Let's say currently there is only one switch in "Building 2." Let's deal with the default situation of no IP address configured on the switch. That means, if there's a problem, you need to:
    1. Run from Building 1 to Building 2
    2. Login using the console cable connected terminal
    3. Troubleshoot
    4. Fix the problem
    5. Run from Building 2 to Building 1.

    So to simplify the above list, you could configure an IP address on the switch so you could either telnet or ssh into the switch from your office in Building 1. However, you'll have to request an IP address from the network engineer/administrator for the switch. Let's say the network engineer/administrator recalculates the subnetting for the entire network so that you can have your IP address for the switch. So the network engineer/administrator finishes resubnetting the entire network and gives you 1 IP address to assign to the switch. Fine, now you can now remotely manage the switch in Building 2 from your office in Building 1.

    Now, once again from an unstackable managed switch perspective, let's say you need to have another switch in Building 2 due to growth. Since the second switch is an unstackable managed switch, once again to help prevent you from running from Building 1 to Building 2 then running from Building 2 to Building 1, you'd like to also remotely manage the second switch, so you're going to need another IP address. So you once again ask your network engineer/administrator for another IP address. Once again, the network engineer/administrator may need to resubnet the entire network, as well as reconfigure the entire networking devices for the new subnetwork scheme, and THEN give you a second IP address. So you take the second IP address, then assign it to the second switch. But not after unplugging the console cable from switch 1 to plug into switch 2 in order to configure the IP address to switch 2. Then you login to the second switch, configure the second IP address to it. Then, you'd need to setup VLAN trunking between switch 2 and switch 1 so you're going to need to find a crossover cable to interconnect switch 2 and switch 1 for the VLAN trunk. Now, you've got two unusuable switch ports because of trunking. Then, unplug the console cable from switch 2 and plug it back into switch 1.

    Guess what? Somehow there's a need for a third switch. So once again, you bother, err, request from the network engineer/administrator another IP address. So the network engineer/administrator resubnets the entire network, and this time, since s/he's so annoyed, s/he assigns you a 4 IP block for the switches in Building 2 so that next time another switch comes, you don't have to bother him/her again. So you do the same process implementing switch 3 as you did with switch 1. Now you've got to configure trunking from switch 3 to switch 2 and switch 3 to switch 1. So you configure the trunks and gotta find another two crossover cables to link switch 3 to switch 2 and switch 3 to switch 1. So far, you've now got 6 unusable switch ports due to trunking. Then you walk back from Building 2 to Building 1.

    Guess what? Somehow there's not only a need for a fourth switch but a FIFTH switch too. Since the network engineer/administrator tried to "allow for growth" for only one more switch, you need to "request" another two IP addresses from the network engineer/administrator. So the network engineer/administrator resubnets the entire network, reconfigures all of the networking devices to the new subnet scheme, then says "Here's an entire block of 14 IP addresses!" So you thankfully sneak out of the network engineer/administrator's office and implement switch 4 and 5 in Building 2. Now you gotta trunk switch 4 to switch 3, trunk switch 4 to switch 2, trunk switch 4 to switch 1, trunk switch 5 to switch 4, trunk switch 5 to switch 3, trunk switch 5 to switch 2, trunk switch 5 to swich 1. With the addition of the 4th switch, you now have 12 unusable switch ports due to trunking. With the addition of switch 5, you now have 20 unusable switch ports due to trunking. To keep this in perspective, that's almost like wasting an entire 24 port switch due to trunking.

    Now, let's compare the unstackable managed switches scenario of the above to the benefits of stackable managed switches. First, for the unstackable managed switches scenario, you needed 1 IP address per switch added to Building 2. With stackable managed switches, you only need the single IP address for the entire stack. So when the second stackable managed switch shows up in your mailbox, you just go plug it into the first switch, then you go back to your office in Building 1. No need to bother, err, request IP addresses from the network engineer/administrator. Second, since all switches in a stack are seen as a single unit, they automatically share VLAN information among themselves so that's another configuration step is removed. Third, since all switches in a stack are seen as a single unit, they automatically trunk with each other through the stack ports without wasting switch ports like unstackable managed switch trunking.

    I hope you now understand the benefits of stackable managed switches vs. unstackable managed switches.
     
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  8. wagnerk
    Highly Decorated Member Award

    wagnerk aka kitkatninja Moderator

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    Ease of managability/centralised management, you just need to remember 1 IP address instead of, say, 50. And you can configure, view and deal with errors thru 1 interface.

    It's very similar to a wireless solution, if you're going to install a site wide solution that needs 50 odd WAP's won't it be alot better to have it centrally managed, rather than configuring each WAP one by one?

    Cisco aren't the only one's doing this, HP Procurves are stackable as well as some D-Links (we've stacked the HP switches at work, but haven't with the D-Links - the D-Link software isn't that great in opinion).

    -Ken
    -Ken
     
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  9. wagnerk
    Highly Decorated Member Award

    wagnerk aka kitkatninja Moderator

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    D**M,

    RHLee beat to the answer by a couple of minutes as well as giving a long answer. Curses... :)

    -ken
     
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