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Beginner

switch HA

Currently i have cisco 3560 switch acting as core switch for some very important business application and it is single point of failure. I am considering getting single or a par of switches that have HA support so in case one switch dies other switch would take over without the need to plug the cables to other switch. Which switch do you recommend for this?

1 ACCEPTED SOLUTION

Accepted Solutions
Participant

Re: switch HA

Hi Damir,

I am sorry you are right 3560 does not support support stacking.

Regarding stack it is like you say. Switches acts as one switch device. If power supply of one switch dies then stack still work without problem.

If master switch of stack dies it takes another switch, depends on priority or configuration of stack.

Best Regards

Jan

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14 REPLIES 14
Participant

Re: switch HA

Hi Damir,

from my point of view you can use two 3560 switches and use StackWise technology for that. Or you can connect this two switches via two normal UTP cables.

Then you can configure etherchannel and connect server one wire to switch one and second wire to switch two. When one of switche will go down traffic should still flow via backup path.

Best regards,

Jan

Beginner

Re: switch HA

Hi Jan,

3560 switches are not stackable, 3750 is. So stackwise provides me HA and multiple switches act as single device ? What happens when power supply dies on one of the switches, does stack continue to function?

Best regards,

Damir

Participant

Re: switch HA

Hi Damir,

I am sorry you are right 3560 does not support support stacking.

Regarding stack it is like you say. Switches acts as one switch device. If power supply of one switch dies then stack still work without problem.

If master switch of stack dies it takes another switch, depends on priority or configuration of stack.

Best Regards

Jan

View solution in original post

VIP Expert

Re: switch HA

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

What happens with power supply failure depends on model of 3560 or 3750 whether it supports redundant power supplies, whether a RPS is being used, and/or whether 3750-Xs are being used with PowerStack.  I.e. there are options to preclude single a power supply dropping taking the 3560/3750 with it.  You might also design to avoid one circuit's power loss taking out units too.

For stacked 3750s, loss of single stack member, for any reason, shouldn't take down rest of stack.

BTW, the 2960S and 3850 support stacking too (different technology).  (The newer 4500-X also supports two units as a single logical unit using VSS.)

You can also design a redundant core with two standalone devices, e.g. a pair of 3560s, but they will operate as two stand alone devices.

Depending on actual design, a stack or VSS might deal with device failure "better" and might provide additional performance over stand alone units.

Beginner

Re: switch HA

Hello Joseph,

i would rather go with stacked devices so they can withstand failure one of the devices but eveything will continue to work. Seems 3570-E is ideal for this, might even consider 3570-X (adittional PSU) but since i will stack them anyway going with 3570-E will save me mony and will get same functionality. Correct?

VIP Expert

Re: switch HA

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

3750 -E and -X are very, very similar, the latter offering PowerStack as a feature.  The -X also offers "modules" where the -E has its "uplink" ports.

Don't know if the -E is still available new.

Hall of Fame Community Legend

switch HA

I would probably stop looking at 3750E/X and start looking into 3850.

3850 is priced the same as a similar 3750X.

Highlighted
Beginner

switch HA

OK 3850 it is then.  I am bit confused with these stacking names, 3750 has stackwise or stackwiseplus, 3850 has powerstack. Is this esentially same thing (failure of 1 device does not break the stack)?

Hall of Fame Community Legend

Re: switch HA

3750X and 3850 have power stack.  Powerstack is for power redundancy (up to four switches).

StackWise/Stackwise Plus is the system that makes multiple switches into a single logical switch.

3750X has Stackwise Plus and has backplane speed of 64 Gbps.

3850 has Stackwise-480 and has backplane speed of 480 Gbps.

Beginner

switch HA

Hi,

so i can conclude that powerstack is not so interested (because it increases the price) since if 1 switch fails with Satckwise i would still have functioning stack (all ports on failed switch would work?).

For using RSTP i need a server with teamed NICs (active/pasive) so each of nics is plugged on separate switches?

Hall of Fame Community Legend

switch HA

so i can conclude that powerstack is not so interested

Power stack minimizes the chance of a member of your stack failing due to a faulty power supply.  So it's up to you.

since if 1 switch fails with Satckwise i would still have functioning stack

Yes, if you have redundant uplinks and your downstream clients are dual homed.

Beginner

switch HA

Aha so there is a catch , in that case i have only 1 uplink and clients have only 1 NIC.

On 3750-x there are cables for Stackwise, but on 3850 i only saw cables for powerstack which look the same as stackwise cables so do you maybe know if stackwise cables are changed for 3850 switch?

Also on backside of 3850 i saw it has 2 PSU, so in theory i don't need to invest in getting 2nd PSU since powerstack will handle powerloss on one switch (i assume both switches have only 1 PSU)?

Participant

Re: switch HA

Jut would like to note that all features has some advantages and also disadvantages. For example 2 days ago I had problem with stack on 3750X-24T-S. One of switch had memory issues. In dump(show stacks) it was called Memory Fragmentation.

Switch worked 2 years well and now it started to reload whole stack when memory was full.So failover does not worked at all.

Everyone will expect that reload will happen just on faulty switch. But in some cases it is not right all stack (2 switches in this case) reloaded. During replacement there was problem how to surely identify what of two switches really reloaded.

So sometimes iwould suggest old fashion solution connect two switches via UTP cable and use RSTP.

Just my experience with stack.

Best regards,

Jan

VIP Expert

Re: switch HA

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

The stack operates running under one IOS, so any software related issue, such as a memory fragmentation, wouldn't normally be resolved by stack member fail over. Cisco has a few IOSs that support a "backup" IOS ready to take over in certain software failure issues.  Don't believe 3750 (or 3850) have such, but they might eventually.

Otherwise, you're correct, the alternative is to use a "classical" separate device design.

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