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Using NCLU to Troubleshoot Your Network Configuration

The Network Command Line Utility (NCLU) can quickly return a lot of information about your network configuration.

net show Commands

Running net show and pressing TAB displays all available command line arguments usable by net. The output looks like this:

cumulus@switch:~$ net show <TAB>
bfd            :  Bidirectional forwarding detection
bgp            :  Border Gateway Protocol
bridge         :  a layer2 bridge
clag           :  Multi-Chassis Link Aggregation
commit         :  apply the commit buffer to the system
configuration  :  settings, configuration state, etc
counters       :  net show counters
debugs         :  Debugs
dot1x          :  Configure, Enable, Delete or Show IEEE 802.1X EAPOL
evpn           :  Ethernet VPN
hostname       :  local hostname
igmp           :  Internet Group Management Protocol
interface      :  An interface, such as swp1, swp2, etc.
ip             :  Internet Protocol version 4/6
ipv6           :  Internet Protocol version 6
lldp           :  Link Layer Discovery Protocol
mpls           :  Multiprotocol Label Switching
mroute         :  Static unicast routes in MRIB for multicast RPF lookup
msdp           :  Multicast Source Discovery Protocol
ospf           :  Open Shortest Path First (OSPFv2)
ospf6          :  Open Shortest Path First (OSPFv3)
package        :  A Cumulus Linux package name
pbr            :  Policy Based Routing
pim            :  Protocol Independent Multicast
ptp            :  Precision Time Protocol
rollback       :  revert to a previous configuration state
route          :  Static routes
route-map      :  Route-map
snmp-server    :  Configure the SNMP server
system         :  System information
time           :  Time
version        :  Version number
vrf            :  Virtual Routing and Forwarding
vrrp           :  Virtual Router Redundancy Protocol

Show Interfaces

To show all available interfaces that are physically UP, run net show interface:

cumulus@switch:~$ net show interface

    Name    Speed    MTU    Mode           Summary
--  ------  -------  -----  -------------  --------------------------------------
UP  lo      N/A      65536  Loopback       IP:,, ::1/128
UP  eth0    1G       1500   Mgmt           IP:
UP  swp1    1G       1500   Access/L2      Untagged: br0
UP  swp2    1G       1500   NotConfigured
UP  swp51   1G       1500   NotConfigured
UP  swp52   1G       1500   NotConfigured
UP  blue    N/A      65536  NotConfigured
UP  br0     N/A      1500   Bridge/L3      IP:
                                           Untagged Members: swp1
                                           802.1q Tag: Untagged
                                           STP: RootSwitch(32768)
UP  red     N/A      65536  NotConfigured

To show every interface regardless of state, run net show interface all:

cumulus@leaf01:~$ net show interface all
State  Name     Spd  MTU    Mode           LLDP                    Summary
-----  -------  ---  -----  -------------  ----------------------  -------------------------
UP     lo       N/A  65536  Loopback                               IP:
        lo                                                         IP:
        lo                                                         IP: ::1/128
UP     eth0     1G   1500   Mgmt           oob-mgmt-switch (swp6)  IP:
UP     swp1     1G   1500   Access/L2      server01 (eth1)         Master: br0(UP)
ADMDN  swp2     N/A  1500   NotConfigured
ADMDN  swp45    N/A  1500   NotConfigured
ADMDN  swp46    N/A  1500   NotConfigured
ADMDN  swp47    N/A  1500   NotConfigured
ADMDN  swp48    N/A  1500   NotConfigured
ADMDN  swp49    N/A  1500   NotConfigured
ADMDN  swp50    N/A  1500   NotConfigured
UP     swp51    1G   1500   Default        spine01 (swp1)
UP     swp52    1G   1500   Default        spine02 (swp1)
UP     br0      N/A  1500   Bridge/L3                               IP:
ADMDN  vagrant  N/A  1500   NotConfigured

To get information about the switch itself, run net show system:

cumulus@switch:~$ net show system
Hostname......... celRED

Build............ Cumulus Linux 4.1.0
Uptime........... 8 days, 12:24:01.770000

Model............ Cel REDSTONE
CPU.............. x86_64 Intel Atom C2538 2.4 GHz
Memory........... 4GB
Disk............. 14.9GB
ASIC............. Broadcom Trident2 BCM56854
Ports............ 48 x 10G-SFP+ & 6 x 40G-QSFP+
Base MAC Address. a0:00:00:00:00:50
Serial Number.... A1010B2A011212AB000001

network-docopt Package

NCLU uses the python network-docopt package. This is inspired by docopt and enables you to specify partial commands without tab completion or running the complete option. For example, net show int runs the net show interface command and net show sys runs the net show system command.