Cisco Catalyst 3850: Understanding Interface Configuration on NM Modules

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It is sometimes confusing on which interfaces are available and which can be configured when using one of the NM modules in a Cisco 3850 Switch. We currently offer three different modules:

C3850-NM-4-1G (four 1-Gigabit SFP module slots)

C3850-NM-2-10G (Combination of 1-Gig and 10-Gig ports)

C3850-NM-4-10G (four 10-Gigabit slots or four 1-Gigabit slots)

The available configuration is based on which model NM you are using. The intent of this document is to help clear up some of the misunderstood configuration options. Below are details on each NM module and how to configure each one when inserted into the switch.

C3850-NM-4-1G:

This module has four 1-Gigabit SFP module slots. Any combination of standard SFP modules are supported. SFP+ modules are not supported. If you insert an SFP+ module in the 1-Gigabit network module, the SFP+ module does not operate, and the switch logs an error message.

C3850-NM-2-10G:

This module has four slots that support the following combinations:

• Two slots (left side) support only 1-Gigabit SFP modules and two slots (right side) support either 1-Gigabit SFP or 10-Gigabit SFP modules.

• Three slots (left side) support 1-Gigabit SFP modules and one slot (right side) supports 10-Gigabit Ethernet SFP+.

Supported combinations of SFP and SFP+ modules:

• Slots 1, 2, 3, and 4 populated with 1-Gigabit SFP modules.

• Slots 1 and 2 populated with 1-Gigabit SFP modules, and Slot 4 populated with one 10-Gigabit SFP+ module.

• Slot 3 and Slot 4 each populated with 10-Gigabit SFP+ modules.

C3850-NM-4-10G:

This module has four 10-Gigabit slots or four 1-Gigabit slots.

Note: This is only supported on the 48-port models.

Configuration:

For the C3850-NM-4-1G module – All ports are natively Gig and are configured as Gig1/1/1 through Gig1/1/4

interface GigabitEthernet1/1/1 <——– Config this interface
!
interface GigabitEthernet1/1/2 <——– Config this interface
!
interface GigabitEthernet1/1/3 <——– Config this interface
!
interface GigabitEthernet1/1/4 <——– Config this interface
!
interface TenGigabitEthernet1/1/1 <——– Disregard
!
interface TenGigabitEthernet1/1/2 <——– Disregard
!
interface TenGigabitEthernet1/1/3 <——– Disregard
!
interface TenGigabitEthernet1/1/4 <——– Disregard

For the C3850-NM-4-10G module – All ports default to 10G and should be configured as
TenGig1/1/1 through TenGig1/1/4 – even though you are operating them as 1G via SFPs.

interface GigabitEthernet1/1/1 <——– Disregard
!
interface GigabitEthernet1/1/2 <——– Disregard
!
interface GigabitEthernet1/1/3 <——– Disregard
!
interface GigabitEthernet1/1/4 <——– Disregard
!
interface TenGigabitEthernet1/1/1 <——– Config this interface
!
interface TenGigabitEthernet1/1/2 <——– Config this interface
!
interface TenGigabitEthernet1/1/3 <——– Config this interface
!
interface TenGigabitEthernet1/1/4 <——– Config this interface

For the C3850-NM-2-10G module – The first two ports are natively 1G ports and the last two ports are natively 10G ports. So you configure the 1Gig ports as Gig1/1/1 through Gig1/1/2, and configure the last two ports as TenGig1/1/3 through TenGig1/1/4 – even if you are operating the last two ports as 1G.

## This is commonly misunderstood ##

interface GigabitEthernet1/1/1 <——– Config this interface
!
interface GigabitEthernet1/1/2 <——– Config this interface
!
interface GigabitEthernet1/1/3 <——– Disregard
!
interface GigabitEthernet1/1/4 <——– Disregard
!
interface TenGigabitEthernet1/1/1 <——– Disregard
!
interface TenGigabitEthernet1/1/2 <——– Disregard
!
interface TenGigabitEthernet1/1/3 <——– Config this interface even if using 1G
!
interface TenGigabitEthernet1/1/4 <——– Config this interface even if using 1G