configuring stacked 3850s

[robertkwild]

hi all,

we have purchased from an old company 7 3850s which are stacked together, they have flattened them so we need to configure them all again

i know how to configure/set up individual cisco switches, so my question is, do i need to console into each individual one seperatly ie set up vlans, ip of the switch, gateway telnet server etc etc or once or i have set up one i can set the rest via this one or do i need to actually console into each one individually

once that is done how do i configure the stacking for the switches so they appear to be one big switch

thanks,

rob

[Reza Sharifi]

Hi Rob,

The first thing I would do I to make sure all the switches have the same exact software version installed, if not, stacking will be difficult. So, upgrade all individual switches to the same version.

The second thing you want to do is to make sure all the switches have the same license level i.e IP base or IP services, etc...

Also, no need to make any configuration changes to individual switches until stacking is completed. Once stacking is done, you just make config changes to the master and the master will sync it to all members.

See these links:

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/3se/ha_stack_manager/configuration_guide/b_hastck_3se_3850_cg/b_hastck_3se_3850_cg_chapter_010.html

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-9/configuration_guide/stck_mgr_ha/b_169_stck_mgr_ha_3850/managing_switch_stacks.html

HTH

[Martin L]

no, no need to do each individually; aka one by one. All other switches get config from the Master switch. Master switch is the one that you apply config to when configuring.  So, Fastest way is to stack them again; then configure only master. The main goal is to have master on the top.  Even if you got order wrong, you can re-number them in the stack without disconnecting which is good practice and a bit tricky.  Read Doc for configuring stack switches.

Regards, ML
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[robertkwild]

ok so let me get this right...

so i stack them all up (top one is master), once i done that, on the top one (the master one) should it find all the other switches, if i have confgiured the stacking correctly ?

and obviously from there when i make any config changes on master one, it goes to all the others aswell?

[Reza Sharifi]

on the top one (the master one) should it find all the other switches, if i have confgiured the stacking correctly ?

No, you want to do the initial stacking provision manually so, you know which is the master and what switches are members based on priority.

example:

sw-1 priority-15 master

sw-2 priority-10 member

sw-3 priority-8 member

sw-4 priority-6 member

This way you know if for whatever reason the master switch (15) fails, the one that becomes the master switch is right below it (10).

So, for each switch, you provision it and add the priority config before connecting the stacking cable. Once this is all done and you can see all switches are correctly stacked from the master, you just configure the master at that point and the master will sync the config to all the members.

also, have a look at the stacking installation guide:

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/hardware/installation/guide/b_c3850_hig/b_c3850_hig_chapter_010.html

HTH

[Martin L · Accepted solution]

Sorry, I should have said Main thing is to have order of switches counting from the top, numbering should be 1,2,3 etc on your telnet CLI.  Otherwise, your tech plugs cable into wrong switch when you tell him "this cable goes into switch 2 port 1".  Master switch can be any switch in stack; Usually is the one on top but doesn't have to be;

Are there any numbering on switches?  If not, turn on the 1st sw on top and wait to see if it is number 1.  If not, re-number it as 1 and reboot.    Then turn on 2nd one from the top and wait to see if joins the stack as number 2.  If not, re-number it as 2 (switch x renumber y) and reboot. 

Note that if switches are wiped out; aka no configs at all or original config out of box, switches will join the stack in sequence of booting them. If you boot all of them at once, the order may get screwed up if they were pre-configured already (aka provisioned). 

Regards, ML
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Master switch

[robertkwild]

ok so first before i connect all the cables in the switches, i first console into every switch individually and on every switch i set the priority of every switch?

[robertkwild]

is it this easy?

https://www.youtube.com/watch?v=dOn_T1izVmQ

connect cables top switch1 to bottom switch7 and then power on switches from top switch1 to bottom switch7 and from master switch it will see the stack and from there you can change switch priority?

[Martin L]

No, Priority matters only for configuration; whose config is applied to others.  Higher priority is applied to all others with lower.  i.e. switch 4 priority 15 wins over sw 1 priority 10. 

Numbering of switches matter the most; this is what you will see when you do show switch command. Numbering of switches is kept in ROMMON mode (switch mode), so it is sort of hard to get to it in order to edit number.  Since those are used ones, they might have labels telling you which is which.

if you console into every switch individually, check numbering of the switches with show switch (also look at interfaces x/0/z where x is number of sw in a stack and z is port #).  You can mark the box with number that is showing in CLI and delete old vlan database file.  Arrange switches with number 1 on top, Then connect stack cables. Power on top switch and check its number. it should be 1, if it is not, u can change it with switch x number 1 and reboot. then check again and power on number 2 switch which should be 2nd from the top. 

Don't worry, you will not break anything.

Regards, ML
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[robertkwild]

If i do this

(Sw)# write erase

(Sw)# delete flash: vlan.dat

(Sw# reload

Will this even delete the stacking of the switches

And if I issue sh run I should see nothing ie no configs

[Martin L]

not sure if write erase or erase is enough in 3850 or you must delete file that stores configs; But, you can try it.

Do dir or show flash: to see files; there should be file named "config.cfg" or something like it.  you can open it to see if that is correct file with configs before deleting files.  do not delete other system files like image.

Regards, ML
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[mlund]

Hi

Martin L has given you an excellent description of how it is function. I will just add some of my thoughts.

There are 2 different components of this, first priority. In my opinion it doesn't matter whish one of the switches in the stack is the master. The one that is the master is the one that can do changes in the configuration and that is the one that you are getting the prompt from. Who is the master ? That depends on how things is setup, or how they are started.

If all switches is started at the same time, then when all comes up and is started to communicate they will elect one that will be the master, and that will be the one with the highest priority. What happens then if the master get lost, then the one of remaining switches with the highest priority will be elected as primary.

When the previous master comes on line again, it will NOT take the master role back, the only way this one will get master again if the current master gets lost.

If the switches starts one after another, the one that is getting on line first will be the master.

Second component is the switch numbering. If switches is unpacked has no configuration, the one that is started first gets number 1, the second one getting online gets number 2, and so on. And as Martin has noted, if numbering is not correct you can change it.

If you start all switches at the same time and they is not have been number before, they will get random numbering.

If the switches has got there numbers, they will remember that number and will use that number every time they get started.

/Mikael

[robertkwild]

Thanks all,

Let's say if I do start again ie factory reset all switches, the next time the switches come back online they should all be stacked up already going by what order there stacked in by the stacking cables?

[mlund]

Hi

No, the order of stacking-cable has nothing to do with how the switches will be numberd

/Mikael

[robertkwild]

So even if I factory wipe switches using the master switch atm, and then it reboots again into brand new config, if I do a

Sh switch

Will it be able to see all the switches or not