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New Member

Increasing number of ports by stacking 2950 and 2960 switches

Need some advice:

We have a small isolated lab environment network, i.e. only machines connected to the network are visible, no external connections.

We currently have a WS-C2950T-48-SI and as the number of machines connected will be increasing soon we will need more than the 48 ports provided by the 2950 switch.

I see that the max ports is on most Cisco switches is 48, so thinking that we should stack another switch on the network in order to add more ports.

Can we stack a 2950 with the recommended replacement, the WS-C2960-48TT-L. If so, is there any documentation on how to connect the two?

The goal would be to make a stack that would appear as a single IP for control purposes.

We currently configure the existing 2950 switch into multiple VLANS, so will need to maintain that capability to create VLANS across the 2 switches.

Thanks in advance for any help.

Everyone's tags (3)
25 REPLIES
Hall of Fame Super Bronze

Increasing number of ports by stacking 2950 and 2960 switches

You won't be able to stack them but you can cluster them, please refer to the documentation:

http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_55_se/configuration/guide/swclus.html

New Member

Increasing number of ports by stacking 2950 and 2960 switches

Thanks for the quick reply. Clustering sounds like the way to go based on the doc link you supplied. 

Another quick question; as I read it, sounds like a cluster is not required to have a cluster standby switch. Sounds optional.

Thanks again.

Hall of Fame Super Bronze

Increasing number of ports by stacking 2950 and 2960 switches

To be honest, I suggest following the documentation and based your design on trial and error.

Very few companies, if any, are going with clustering switches design anymore.

I can't offer much guidance on caveats presented when clustering, sorry.

Bronze

Increasing number of ports by stacking 2950 and 2960 switches

Hi Randy,

2950/60 are not stackable switches.

However 2960-S can use FlexStack to add switches into stack, but doesn't behave like StackWise which is in 3750 stackable switches.

Thanks,

Manju

Hall of Fame Super Gold

Increasing number of ports by stacking 2950 and 2960 switches

I agree with Edison's post.  Your only option is "clustering" but even then, I don't see any reason to do so.

The only convinience with "clustering" is when you are have limited amount of management IP address.  Otherwise, this is no longer applicable in modern day technology.

New Member

Increasing number of ports by stacking 2950 and 2960 switches

For our small network we really only need a managed switch that has more than 48 ports. I need to be able to create multiple VLANs. We already have the 2950 switch, so thought the best way to extend it to more ports would be to stack (or cluster). If there is a simpler option that will still allow me to create multiple VLANs across the 2 switches, I am all for it.

Hall of Fame Super Bronze

Re: Increasing number of ports by stacking 2950 and 2960 switche

Randy Brandenburg wrote:

For our small network we really only need a managed switch that has more than 48 ports. I need to be able to create multiple VLANs. We already have the 2950 switch, so thought the best way to extend it to more ports would be to stack (or cluster). If there is a simpler option that will still allow me to create multiple VLANs across the 2 switches, I am all for it.

You can deploy multiple switches in your network supporting multiple Vlans without the need for clustering.

Clustering allows you to assign one IP address to all switches for centralized management.

You can still achieve the same functionality (multiple vlans, multiple switches)

by having each switch with an unique IP address and manage them independently.

While on the subject of creating multiple Vlans, please do not consider using VTP Server/Client model.

Change your VTP mode to transparent and manually create the Vlans on each of the physical switches.

The Server/Client model can create outages in your network rather easily because any switch can assume

a VTP Server role and can potentially wipe out the Vlan from other production switches.

Regards,

Edison

Hall of Fame Super Gold

Increasing number of ports by stacking 2950 and 2960 switches

 I need to be able to create multiple VLANs.

Ummmm ... who's doing the routing?  I mean, granted, the 2960/2960G/2960S can perform "limited" routing but you still need something route traffic from one VLAN to another.

2960S is, in my opinion, the most affordable Layer 2 switch that will do stacking (it's better than clustering).

A few caveats umptor:

1.  Stack backplane is 10Gbps, full duplex;

2.  You CANNOT stack 5 or more (maximum stacking limit is 4); and

3.  You can stack only 2960S.  You cannot stack 2960S with, say, 2960 or 2960G or 3560 (all models) or 3750 (all models) and definitely NOT the 4500 and 6500.

New Member

Increasing number of ports by stacking 2950 and 2960 switches

Thanks for the discussion; After browsing the Catalyst 2960 and 2960-S Switches Software Configuration Guide sections about creating VLANs and about creating a trunk interface port between switches, I think I have a basic undertsanding of how to proceed with/without clustering the switches. As Edison suggests, it will take some trial and error, but the basic requirements I have should be attainable.

Super Bronze

Re: Increasing number of ports by stacking 2950 and 2960 switche

Disclaimer

The    Author of this posting offers the information contained within this    posting without consideration and with the reader's understanding that    there's no implied or expressed suitability or fitness for any  purpose.   Information provided is for informational purposes only and  should not   be construed as rendering professional advice of any kind.  Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In    no event shall Author be liable for any damages whatsoever  (including,   without limitation, damages for loss of use, data or  profit) arising  out  of the use or inability to use the posting's  information even if  Author  has been advised of the possibility of such  damage.

Posting


Generally, you can just connect one switch to another to increase available ports.  If they are manageable switches, you have more "devices" to configure vs. actual stacked (or clustered) switches.

When you connect switches, you can get into other considerations such as bandwidth between switches, extending VLANs, redundancy, and optimal (fewest) hops between devices.  But for just two switches, you might not need to consider any of this.

New Member

Increasing number of ports by stacking 2950 and 2960 switches

Anyone have a feel for the performance difference between a 2 switch cluster and a 2 switch stack? If any?

Also, can a cluster of  2960 switches be configured via SSH? I see references to configuring via CLI, so assume SSH is possible, just as a console cable or telnet?

Thank you.

Hall of Fame Super Gold

Re: Increasing number of ports by stacking 2950 and 2960 switche

Anyone have a feel for the performance difference between a 2 switch cluster and a 2 switch stack? If any?

Like I've said before, "clustering" is old-school.  Other than the fact that the only major benefit with "clustering" is the usage of management IP addresses.  This is the same with switch stacking (like the 2960S and the 3750 family).

The downside with "clustering" is the size of your uplink to cluster one from the other.  So if your switch is clustered using 100 Mbps then this is your cluster "speed".  If you have 1000 Mbps then this is your cluster "speed".  With stacking, it is far superior.  How?

1.  Your backplane stacking is between 10 Gbps (2960S), 16 Gbps (3750, 3750G) or 32 Gbps (3750E/3750X) full duplex; and

2.  Configuration management - With switch stack, you configure your entire stack from the master switch stack or from one logical unit.  With switch clustering, you configure each individual cluster member separately.

This is the main reason why people who's have experience with "clustering" will readily dump this in favour of switch clustering.  (Heck, some people may just feign "ignorance" when asked this question!)

Also, can a cluster of  2960 switches be configured via SSH? I see references to configuring via CLI, so assume SSH is possible, just as a console cable or telnet?

Yes, you can configure a cluster of plain 2960 from SSH provided you are running "Crypto" IOS and have SSH enabled.  You can do so either console and/or Telnet.  Again, because you are dealing with "clustering" you may need to configure each individual cluster member for SSH.

New Member

Increasing number of ports by stacking 2950 and 2960 switches

Thanks for taking the time to answer my questions. I want to understand this completely so please bear with me - I was thrust into this switch research with very little experience (if you couldnt tell)....

So, on a cluster of 2 switches, the max switching speed between the 2 switches would be the speed of the port that I connect the 2 switches together (e.g., one of the G-bit ports). So traffic from devices connected to a port on switch A (100 Mbps)  to a device on switch B (also connected on the 100Mbps port), would effectovely be 100Mbps (max of 1000Gbps).

The only thing that is making me cling to the clustering setup is cost. I need to buy 16 switches (will connect 2 per site). Expansion above 2 switches per site is very -very unlikely. Also, all network traffic will be local to the 2 switches which will be installed in a isolated lab environment with all machines are on the same subnet. 

I will suggest going with the 2960-S, so that if needed in the future, we can stack them, but will probably use clustering for now. I think buying the stack modules in addition to the switches would be cost prohibitive for our project.

Hall of Fame Super Gold

Re: Increasing number of ports by stacking 2950 and 2960 switche

So traffic from devices connected to a port on switch A (100 Mbps)  to a device on switch B (also connected on the 100Mbps port), would effectovely be 100Mbps (max of 1000Gbps).

Remember the devices that are connected to switch A has to SHARE the bandwidth of the uplink.  For instance, your devices/clients in Switch A are connected to 1 Gbps interface and your uplink are two  1 Gbps interface.   IT's OK if the traffic is sporadic, but what if people are sending large chunks of files to and from each other or watching HD video?

The only thing that is making me cling to the clustering setup is cost. I need to buy 16 switches (will connect 2 per site). Expansion above 2 switches per site is very -very unlikely. Also, all network traffic will be local to the 2 switches which will be installed in a isolated lab environment with all machines are on the same subnet.

I honestly don't have any idea what is the maximum number of switches you can "cluster" nowadays.  Back then it was limted to the GigaStacking GBIC cable.  But stacking 16 switches is a very, very, very, very bad design.  Heck, stacking more than 9 is just, for the lack of a better word, dumb.  (Sorry for my choice of word.)

The only thing that is making me cling to the clustering setup is cost.

Then why bother stacking?  Why don't you just give each of your switches a management IP address, put them all in one VLAN and be done?   Ensure your uplinks are all in a trunk.

I will suggest going with the 2960-S, so that if needed in the future, we can stack them, but will probably use clustering for now. I think buying the stack modules in addition to the switches would be cost prohibitive for our project.

Talk to the local Cisco office (not your local authorized Cisco reseller).  There are so many ways for you to get discounts from Cisco.

1.  Technology Migration Program;

2.  Educational Institution;

3.  Cisco Refurbished

New Member

Re: Increasing number of ports by stacking 2950 and 2960 switche

Leo,

I think I owe some clarifications.

Then why bother stacking?  Why don't you just give each of your switches a management IP address, put them all in one VLAN and be done?   Ensure your uplinks are all in a trunk.    

The software we run will require the available switch-ports to be configured into multiple VLANs. So a single VLAN will not meet my requirements.

 But stacking 16 switches is a very, very, very, very bad design

Will only be stacking/clustering 2 switches. 

New Member

Re: Increasing number of ports by stacking 2950 and 2960 switche

I think that the 2960-S switch is an excellent choice, even if you do not buy the stacking modules at this stage. The

48TS-L model has 48 ports and 4 separate uplink ports (not shared). It also has a separate isolated management port which we like.

If you are buying several switches then I would buy the modules and stack up to four in one location. This creates the appearance of one switch and it makes management and performance considerably better.

If you have two or more switches I would disagree with Edison and recommend that you use VTP (properly configured) and nominate two switches as servers with a shared domain name.

Daniel

Hall of Fame Super Gold

Re: Increasing number of ports by stacking 2950 and 2960 switche

The software we run will require the available switch-ports to be configured into multiple VLANs. So a single VLAN will not meet my requirements.

My deepest apologies ... but I still don't see where "switch clustering" fits in.  Let me get this straight (pass the coffee), each ports connected to your software requires multiple VLANs, for example, 300, 400, 500?

If this is the case then configure the ports of your choice into a 802.1q Trunk.

Let me see ... With a 2960, you'll just need to enter the command "switchport mode trunk" and this will enable the port to use multiple VLANs per port.  You can also "specify" which VLANs you want using the optional command of  "switchport trunk allowed vlan 300-400,500".

Is this what you are looking for?

New Member

Re: Increasing number of ports by stacking 2950 and 2960 switche

No problem, I am equally confused I think.I'll try to explain. This isnot a normal network setup at all.

In a nutshell our "systems" consist of a mix of ~ 55 PCs and Sun servers. Our new requirement is that each system shall be capable of being separated into up to 3 standalone systems, e.g. machines 1,2,3,4,5..20 would be on vlan 300, machines 21-35 would be on vlan 400, and the rest on vlan 500.

The goal is to be able to run up to 3 "systems" simultaneously using the same hardware. Since the software running on all 3 systems will be identical. The 3 vlans would need to be isolated so that they appear to be 3 separate networks.

I realize this is a special case, but those are the requirements for our training systems.

New Member

Re: Increasing number of ports by stacking 2950 and 2960 switche

Randy

As I understand it, this is a completely normal use case for VLANs. You need to add your second switch and connect it via at least one cable. An etherchannel would make sense to get more throughput. You do not need to do stacking or clustering.

You will need to build the same VLANs on each switch and trunk them all over the link. This is normal deployment. You can do this manually or using VTP.

Important - you will need to consider how these VLANs will talk to each other, if necessary. You will need some separate routing device that has all the VLANs trunked to it.

Daniel

Hall of Fame Super Gold

Re: Increasing number of ports by stacking 2950 and 2960 switche

Alright Randy.  I get what you are trying to do.  But I believe switch "clustering" is out of the question.

1.  If you have two (or more) switches then you may have to configure 802.1Q Trunking.

2.  Next you need a Layer 3 device to do routing or the three VLANs will not talk to each other.

3.  Since you have two switches you may (optionally) configure etherchannel (just as Daniel has posted).

Wait a second ... Did you say 2960???  Ok, load the 12.2(55)SE3, SE4 or SE5 and you'll be able to do limited routing.

With only three VLANs, it could save you some money buying a router.

New Member

Re: Increasing number of ports by stacking 2950 and 2960 switche

Gentlemen,

OK, a few more questions/clarifications to your comments.

MY boss wnats the cleanest install / configuration possible. For each site, if I buy 2 Catalyst 2960 (and ditch the 2950), upgrade the IOS to the version Leo suggests, and given the following clarifications, what is the bottom line equipment I would need to acommplish my requirement of 3 independent VLANs and support for up to 55 PCs/Suns attached.

You need to add your second switch and connect it via at least one cable. An etherchannel would make sense to get more throughput

Was planning on using the Gbit port on the 2960.

You will need to consider how these VLANs will talk to each other, if necessary. 

Based on our requirements they will not need to talk to each other - i.e., machines on VLAN 300 will not be able to see machines on VLAN 400 or 500.

2. Next you need a Layer 3 device to do routing or the three VLANs will not talk to each other.

The machines on each VLAN need to be isolated from each other, see above.

Wait a second ... Did you say 2960???  Ok, load the 12.2(55)SE3, SE4 or SE5 and you'll be able to do

limited routing.

Yes, the 2960 is what Cisco recommends updating to on thier web-site.

I really appreciate your guys' comments and suggestions !

New Member

Re: Increasing number of ports by stacking 2950 and 2960 switche

MY boss wnats the cleanest install / configuration possible. For each  site, if I buy 2 Catalyst 2960 (and ditch the 2950), upgrade the IOS to  the version Leo suggests, and given the following clarifications, what  is the bottom line equipment I would need to acommplish my requirement  of 3 independent VLANs and support for up to 55 PCs/Suns attached.

The cleanest configuration possible, in my opinion, is to buy two new C2960S 48 port switches with stacking modules and connect them in a stack. This will effectively one 96 port switch with a single management interface. You can connect to it using the management ethernet port and not even enter the lab network from your desk.

You will create three VLANs in additon to VLAN 1, which I would not use for any of the ports.

You will not need an additional linking cable or etherchannel. You will not need to use any of the switch ports for linking.

Based on our requirements they will not need to talk to each other -  i.e., machines on VLAN 300 will not be able to see machines on VLAN 400  or 500.

The machines on each VLAN need to be isolated from each other, see above.

Then you will not need any routing device. Bear in mind that any firewall/gateway you have on the lab network will need to be replicated on the new VLANs. You should not need the routing features of the C2960S.

Daniel

Hall of Fame Super Gold

Re: Increasing number of ports by stacking 2950 and 2960 switche

I agree with Daniel.

If you have the funds, get the 2960S and the stacking modules.  This is one LESS configuration headache when you stack them together PLUS when you configure the two units, you only do your configuration in ONE.

The machines on each VLAN need to be isolated from each other, see above.

This is not rocket-scientist.  If each of the three VLANs are not meant to talk to each other then you don't need routing.  Just configure each port to their corresponding VLANs so each VLAN will only talk to their own VLAN.

Super Bronze

Re: Increasing number of ports by stacking 2950 and 2960 switche

Disclaimer

The     Author of this posting offers the information contained within this     posting without consideration and with the reader's understanding  that    there's no implied or expressed suitability or fitness for any   purpose.   Information provided is for informational purposes only and   should not   be construed as rendering professional advice of any kind.   Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In     no event shall Author be liable for any damages whatsoever   (including,   without limitation, damages for loss of use, data or   profit) arising  out  of the use or inability to use the posting's   information even if  Author  has been advised of the possibility of  such  damage.

Posting

So, on a cluster of 2 switches, the max switching speed between the 2 switches would be the speed of the port that I connect the 2 switches together (e.g., one of the G-bit ports). So traffic from devices connected to a port on switch A (100 Mbps)  to a device on switch B (also connected on the 100Mbps port), would effectovely be 100Mbps (max of 1000Gbps).

Yes and no.  Many manageable switches support bundling multiple ports to increase aggregate bandwidth.  Even when this isn't done, the situation often is not dire since you still need to consider the bandwidth on uplinks from a chassis or stacked switches.  In other words, links to/from your location often bottleneck before links at the location.

The only thing that is making me cling to the clustering setup is cost. I need to buy 16 switches (will connect 2 per site). Expansion above 2 switches per site is very -very unlikely. Also, all network traffic will be local to the 2 switches which will be installed in a isolated lab environment with all machines are on the same subnet. 

The major "disadvantage" of your extra "logical" switches would be the need to assign twice as many switch management IPs.  (NB: this assumes 2 IPs per location rather than just 1 IP per location.)

BTW, what you've described as desiring to do was routinely done before clustering or switch stack technology was available.


I will suggest going with the 2960-S, so that if needed in the future, we can stack them, but will probably use clustering for now. I think buying the stack modules in addition to the switches would be cost prohibitive for our project.

Stacking often offers nice features beyond just conservation of management IPs, although 2960 might not be as nice as Stackwise(+) available in the various 3750 series.

New Member

Re: Increasing number of ports by stacking 2950 and 2960 switche

Well, based on the comments and suggestions from this thread, I will go with two 2960S switches. Initially I wont be able to afford the stacking modules, but may upgrade at a later time.

I will trunk the two ports together via the gigabit port and deal with extra config (changes in the config are not very likely after the intial setup).

leo and Dan, thanks for all your paitence and good advice - I now have a better understanding of the problem and how to go about addressing it.

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