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New Member

Redundant Switch Configuration

I'm trying to setup two Catalyst 3750X-48T-L switches to support redundant networking.  Most pieces of equipment will have two Ethernet interfaces, each on separate subnets.  

So far, I've got the switches configured as separate VLANs, connected together with stack cables as shown below.  I can propagate Ethernet traffic in each subnet/VLAN independently.  However, I cannot get packets routed across the VLANs/subnets.


I'm looking for guidance on what additional steps are needed.  Do I need to define each port as a trunk connection?

Everyone's tags (1)
Hall of Fame Super Silver

Do you have layer 3

Do you have layer 3 interfaces (SVIs - i.e "interface vlan 28" , "interface vlan 29" each with IP addresses) on the switches? Otherwise you have disjoint L2 domains with no way to route between them.

Also if you have the switches in a stack with stacking cables there is only only one logical switch stack - not two separately configured switches.

New Member

Yes, I am using stack cables

Yes, I am using stack cables and have 1 "logical switch".  

VLAN 28 has IP address  I will have to verify, but I think VLAN 29 has IP address


Hall of Fame Super Silver

Please share:show ip int br |

Please share:

show ip int br | ex una

show run int <interface connecting to SBC 2>

show int <interface connecting to SBC 2>

New Member

Attached are outputs from the

Attached are outputs from the three commands.

Hall of Fame Super Blue

If you want to route between

If you want to route between the vlans then you need to have L3 vlan interfaces (SVIs) on the switches.

So for each vlan you need to create an SVI and assign it an IP address from the IP subnet used for that vlan.

Then you set the default gateway of the clients in that vlan to the be the SVI IP address.

Note - if your switches are stacked you only need to create the SVIs on the stack master.

Edit - haven't used 3750-X switches so you many also need to enable IP routing using the "ip routing" command.


New Member

I don't think the 3750-X have

I don't think the 3750-X have the "ip routing" command, or maybe I entered it at the wrong level.  

See my reply below that shows both VLANs have IP addresses.  Is that equivalent to the SVIs you mention?

New Member

The 3750X-48T-L is LAN Base

The 3750X-48T-L is LAN Base.
It is not Layer 3.
You need either the IP Base (3750X-48T-S) or IP Services (3750X-48T-E) license in order to route.

New Member

I apologize if this is a

I apologize if this is a silly question:

Is routing absolutely necessary for what I wish to do?  

Or is some other solution possible (like EtherChannel) ?

New Member

Solution: I ended up loading

Solution: I ended up loading the IP Base IOS image to the switches so that I could enable the "ip routing" function.  I added all ports of both switches to the same VLAN, rather than separate VLANs.  I gave the stacked "switch" two IP addresses, one in each subnet.