04-02-2014 11:13 AM - edited 03-07-2019 06:58 PM
Hi everyone
I am reading about switch stack technology and i have some questions about high availability feature
I dont really understand how stack technology can provide this feature (i mean HA for data traffic, not only for device management)?
Can somebody help me make clear about this?
Thank you very much!
TrungNQ
Solved! Go to Solution.
04-03-2014 07:05 AM
That is right. If you cross connect your access switches to the core stack using portchannels,, than you don't need to worry about STP, HSRP, VRRP, etc..
The down time is very minimum in case there is a link failure..
HTH
04-02-2014 11:29 AM
HA is available for management traffic and any routing configuration as each switch in the stack is capable of being the master should the current active master fail. The next elected master would take over any routing or layer 3 interfaces and continue to function. Any devices that are connected to a failed switch would lose their connectivity until physically moved to another switch in the stack. If this is a concern, you would normally dual-home devices connected to the stack, if possible.
Some data high availability is achieved through the StackWise cables on the back of the switch. All data is efficiently load balanced across the StackWise uplinks for data that needs to traverse through an uplink to somewhere else on the network. If one StackWise port fails, the traffic would automatically be redirected across the other StackWise port.
Hope this helps.
04-03-2014 05:16 AM
Thank you very much for all of your answers
As I understand, stack will:
- Make several switch act as 1 big switch ( if i have 2 switch 24 port, when they are stacked, i will have a big switch with 48 port)
- Single point of management( all configuation just do one time, upgrade also)
- Stack bus (Cable plug in stack module to connect 2 switch), it just a very high speed link, high bandwidth; it better than us etherchannel to connect 2 standalone switch( maximum 8 link). ???. It also use to "feel" to determine when 1 switch is down and remove it out of stack, right?
I have a topology:
- My server is configed NIC teaming (mode active-standby) with 1 ip address. 2 NIC is linked to 2 difference standalone switch. Each switch have a way out. If i use switch stack, in case of 1 uplink down, switch will feel it and automatic use the uplink in other switch to traffer data from my server in the way out?
Thank you for your support!!!
04-03-2014 05:53 AM
Hello Nguyen,
As per your topology , if we replace stack switch in place of two different standalone switches. If all the ports in the uplink and the stack switch are in STP the switch will detect and will change the state of the blocking port to forwarding.
However i will suggest to use port channel if the upstream topology supports to take the advantage of load balancing of both the links.
regards
Parhta
04-03-2014 06:57 AM
So the benefit of stack about HA feature is about cross-etherchannel, avoid stp to make the down time smalless, right ?
04-03-2014 07:05 AM
That is right. If you cross connect your access switches to the core stack using portchannels,, than you don't need to worry about STP, HSRP, VRRP, etc..
The down time is very minimum in case there is a link failure..
HTH
04-03-2014 07:25 AM
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.
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Posting
Yes, stack cables generally provide more bandwidth. In original 3750 series, each stack port is (I believe) 8 Gbps, duplex. In 3750 -E/-X series, each stack port is (I believe) 16 Gbps, duplex. When both cables are connected, both are used.
Unsure about your "feel" or determining when a stack member fails question.
For your current server topology, you might find you can use both server ports, actively, if connecting to a stack. Otherwise it should mimic your two switch topology.
04-03-2014 07:48 PM
Hi Joseph
My question is: how master know when a stack member down and remove it away from the stack. As i understand, master use the path thought the stack cable to healthcheck other member in stack. Is it corect?
Thank you!
04-04-2014 02:46 AM
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
Yes, stack master will "know" when a provisioned switch member or members is not part of stack. When both stack ports are connected and only one stack member fails (or stack link), stack will function w/o failed stack member. If only one stack port is connected and stack member fails (or stack link), stack may partition and run as two stacks (believing themselves to be the "original" stack - you don't want that!).
04-02-2014 11:34 AM
Hi,
when you stack multiple switches, they logically become one switch. So you are managing only one switch. As far as the data traffic goes, you need to connected your devices to multiple devices in the stack to take advantage of it. Say you have 2 switches stacked in your core, and 5 switches (not stacked) at the access later, you would need to connect your uplinks from each access switch to both core switches to take advantage of high availability.
HTH
05-28-2019 04:34 AM
Hello,
I'm just taking this information a bit deep. Setup remains the same i.e. two core switches are stacked and 5 switches which are access switches and not stacked. These 5 access switches have one uplink to switch-1 in core stack and second uplink to switch-2 in core stack. Now, if I configured SVI in switch-1 (which is assumed to be master in stack) and the IP address of SVI is used as a default gateway in LAN devices then if switch-1 in stack fails will LAN devices send traffic to switch-2 in core stack?
05-28-2019 09:47 AM
04-02-2014 12:12 PM
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
When an individual stack members fails, it fails, sort of, like a failed line card on a chassis. The other stack members continue to function.
One of stack members acts as the "brains" for the whole stack. As noted by the other posters, if this stack member fails, another stack member takes over, much like a second supervisor in a chassis.
Lastly, the 3750X series can also share power within their stack. So, even if a power supply fails in a 3750X, that unit might continue to function normally, even while supporting PoE, much like a chassis with redundant power supplies.
As mentioned by the other posters, to fully leverage a stack's redundancy for data traffic, devices connecting to the stack would have at least two connections, and all the connections wouldn't be to the same stack member. (NB: basically simiar considerations if using a chassis with redundancy or a VSS pair.)
Of course you can also provide data traffic redunancy with multiple network devices too, but a stack is one device to manage rather than N devices to manage and often provides improved bandwidth between stack members and sometimes also between the stack and other devices (the latter using Etherchannel).
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