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How To Connect 2 Switch Stacks Over Ethernet?

N3TWORK3D
Level 1
Level 1

Hi,

 

I have 2 switch stacks (2 3850s in each), on different floors.

 

What is the best way to connect them and how do I properly configure the ports?

 

If Ethernet, can I bond the ports to provide more throughput? What about cross over cable?

 

Thanks!

1 Accepted Solution

Accepted Solutions

Predrag Jovic
Level 3
Level 3

Create etherchannel between switches (one link from each switch).

Stack 1

interface range Gi1/0/49, Gi2/0/49

 shutdown

 switchport mode trunk

 channel-group 1 mode active

 no shutdown

 

Stack 2

interface range Gi1/0/49, Gi2/0/49

 shutdown

 switchport mode trunk

 channel-group 1 mode active

 no shutdown

 

Generally you can, but don't have to use crossover cables. Auto-MDIX is default on Cisco devices (except for SFP -SX and -LX  module interfaces).

View solution in original post

6 Replies 6

Predrag Jovic
Level 3
Level 3

Create etherchannel between switches (one link from each switch).

Stack 1

interface range Gi1/0/49, Gi2/0/49

 shutdown

 switchport mode trunk

 channel-group 1 mode active

 no shutdown

 

Stack 2

interface range Gi1/0/49, Gi2/0/49

 shutdown

 switchport mode trunk

 channel-group 1 mode active

 no shutdown

 

Generally you can, but don't have to use crossover cables. Auto-MDIX is default on Cisco devices (except for SFP -SX and -LX  module interfaces).

Awesome! Thanks for the quick response.

Can you tell me though what 1/0/49 is? My switch is only goes up to 1/0/48 or is that just a way to say any port?

You're welcome.

 

On 48 port switch Gi1/0/49-52 are typically SFP uplink ports (fiber or copper connection, can have 10Gb ports, on 3850 models uplink module is not built in).

 

3850 architecture details:

Cisco Catalyst 3850 Series - Switches StackWise - 480 Architecture

on Cisco live (need to have account there  (but, it is free registration)):

Cisco Catalyst 3850 and 3650 Switching Architecture

Oh gotcha. I actually have them as 1/1/1-4 and 2/1/1-4

 

So then are you suggesting that I only use the SFP uplink ports? I do not have those adapters. I am curious if I can use one port from each switch in the stack to create the EtherChannel over to the other switch stack.

 

Thanks.

It is general recommendation to use uplink ports.

And, yes, you can create ehterchannel from different stack switches to other devices (and it is, most of the time, recommended to do so).

As also noted by Predrag, yes you can use regular copper ports both in Etherchannels and to interconnect switches. Cannot say for certain for a 3850, but on the earlier 3750 series, Cisco had 2 MB RAM buffers per 24 copper ports or for its module ports. I.e. module ports might have more and/or better hardware resources backing them because they are most often used for uplinks and often carry more traffic than copper edge ports.

Predrag also showed using your Etherchannel as a L2 trunk, but since a 3850 is a L3 switch, you should also have the option to use a Etherchannel as a L3 link too.

Lastly, I don't know what the default load balancing hashing algorithm is for a 3850, but you might want to confirm, if more than one algorithm is available, you're using the optimal algorithm for your traffic.
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