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>
    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       :  show netstat counters
    hostname       :  System hostname
    igmp           :  Internet Group Management Protocol
    interface      :  An interface such as swp1, swp2, etc
    ip             :  Internet Protocol version 4
    ipv6           :  Internet Protocol version 6
    lldp           :  Link Layer Discovery Protocol
    lnv            :  Lightweight Network Virtualization
    mroute         :  Configure static unicast route into MRIB for multicast RPF lookup
    msdp           :  Multicast Source Discovery Protocol
    ospf           :  Open Shortest Path First (OSPFv2)
    ospf6          :  Open Shortest Path First (OSPFv3)
    pim            :  Protocol Independent Multicast
    rollback       :  revert to a previous configuration state
    route          :  Static routes
    route-map      :  Route-map
    system         :  System information
    version        :  Version number

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: 10.0.0.11/32, 127.0.0.1/8, ::1/128
UP  eth0    1G       1500   Mgmt           IP: 192.168.0.11/24(DHCP)
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: 172.16.1.1/24
                                           Untagged Members: swp1
                                           802.1q Tag: Untagged
                                           STP: RootSwitch(32768)
UP  red     N/A      65536  NotConfigured

Whereas net show interface all displays every interface regardless of state:

cumulus@switch:~$ net show interface all
       Name     Speed    MTU    Mode           Summary
-----  -------  -------  -----  -------------  --------------------------------------
UP     lo       N/A      65536  Loopback       IP: 10.0.0.11/32, 127.0.0.1/8, ::1/128
UP     eth0     1G       1500   Mgmt           IP: 192.168.0.11/24(DHCP)
UP     swp1     1G       1500   Access/L2      Untagged: br0
UP     swp2     1G       1500   NotConfigured
ADMDN  swp45    0M       1500   NotConfigured
ADMDN  swp46    0M       1500   NotConfigured
ADMDN  swp47    0M       1500   NotConfigured
ADMDN  swp48    0M       1500   NotConfigured
ADMDN  swp49    0M       1500   NotConfigured
ADMDN  swp50    0M       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: 172.16.1.1/24
                                               Untagged Members: swp1
                                               802.1q Tag: Untagged
                                               STP: RootSwitch(32768)
UP     red      N/A      65536  NotConfigured
ADMDN  vagrant  0M       1500   NotConfigured

You can get information about the switch itself by running net show system:

cumulus@switch:~$ net show system
Hostname......... celRED
 
Build............ Cumulus Linux 3.7.4~1551312781.35d3264
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

Other Useful Features

NCLU uses the python network-docopt package. This is inspired by docopt and provides the ability to specify partial commands, without tab completion and running the complete option. For example:

net show int runs netshow interface
net show sys runs netshow system

Install netshow on a Linux Server

netshow is a tool for troubleshooting networks. In Cumulus Linux, it’s been replaced by NCLU. However, NCLU is not available on Linux hosts at this time, so use netshow to help troubleshoot servers. To install netshow on a Linux server, run:

root@host:~# pip install netshow-linux-lib