Arista cEOS#

Arista cEOS is identified with ceos kind in the topology file. The ceos kind defines a supported feature set and a startup procedure of a ceos node.

cEOS nodes launched with containerlab comes up with

• their management interface eth0 configured with IPv4/6 addresses as assigned by docker
• hostname assigned to the node name
• gNMI, Netconf and eAPI services enabled
• admin user created with password admin

Managing ceos nodes#

Arista cEOS node launched with containerlab can be managed via the following interfaces:

docker exec -it <container-name/id> bash

docker exec -it <container-name/id> Cli

ssh root@<container-name> -p 830 -s netconf

gnmic -a <container-name/node-mgmt-address>:6030 --insecure \
-u admin -p admin \
capabilities

Interfaces mapping#

ceos container uses the following mapping for its linux interfaces:

• eth0 - management interface connected to the containerlab management network
• eth1 - first data interface

When containerlab launches ceos node, it will set IPv4/6 addresses as assigned by docker to the eth0 interface and ceos node will boot with that addresses configured. Data interfaces eth1+ need to be configured with IP addressing manually.

bash-4.2# ip address
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/24 scope host lo
    valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
    valid_lft forever preferred_lft forever
<SNIP>
5877: eth0@if5878: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
    link/ether 02:42:ac:14:14:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 172.20.20.2/24 brd 172.20.20.255 scope global eth0
    valid_lft forever preferred_lft forever
    inet6 2001:172:20:20::2/80 scope global
    valid_lft forever preferred_lft forever
    inet6 fe80::42:acff:fe14:1402/64 scope link
    valid_lft forever preferred_lft forever

ceos>sh ip int br
                                                                            Address
Interface         IP Address           Status       Protocol           MTU    Owner
----------------- -------------------- ------------ -------------- ---------- -------
Management0       172.20.20.2/24       up           up                1500

ceos>sh ipv6 int br
Interface       Status        MTU       IPv6 Address                     Addr State    Addr Source
--------------- ------------ ---------- -------------------------------- ---------------- -----------
Ma0             up           1500       fe80::42:acff:fe14:1402/64       up            link local
                                        2001:172:20:20::2/80             up            config

Additional interface naming considerations#

While many users will be fine with the default ceos naming of eth, some ceos users may find that they need to name their interfaces et. Interfaces named et provide consistency with the underlying interface mappings within ceos. This enables the correct operation of commands/features which depend on et format interface naming.

In order to align interfaces in this manner, the INTFTYPE environment variable must be set to et in the topology definition file and the links which are defined must be named et, as opposed to eth. This naming requirement does not apply to the eth0 interface automatically created by containerlab. This is only required for links that are used for interconnection with other elements in a topology.

example:

topology:
  defaults:
    env:
      INTFTYPE: et
  nodes:
  { ... snipped misc. node definition for brevity ... }
  links:
    - endpoints: ["ceos_rtr1:et1", "ceos_rtr2:et1"]
    - endpoints: ["ceos_rtr1:et2", "ceos_rtr3:et1"]

Features and options#

Node configuration#

cEOS nodes have a dedicated config directory that is used to persist the configuration of the node. It is possible to launch nodes of ceos kind with a basic config or to provide a custom config file that will be used as a startup config instead.

Default node configuration#

When a node is defined without config statement present, containerlab will generate an empty config from this template and copy it to the config directory of the node.

# example of a topo file that does not define a custom config
# as a result, the config will be generated from a template
# and used by this node
name: ceos
topology:
  nodes:
    ceos:
      kind: ceos

The generated config will be saved by the path clab-<lab_name>/<node-name>/flash/startup-config. Using the example topology presented above, the exact path to the config will be clab-ceos/ceos/flash/startup-config.

cEOS Ma0 interface will be configured with a random MAC address with 00:1c:73 OUI part. Containerlab will also create a system_mac_address file in the node's lab directory with the value of a System MAC address. The System MAC address value is calculated as Ma0-MAC-addr + 1.

User defined config#

It is possible to make ceos nodes to boot up with a user-defined config instead of a built-in one. With a startup-config property a user sets the path to the config file that will be mounted to a container and used as a startup config:

name: ceos_lab
topology:
  nodes:
    ceos:
      kind: ceos
      config: myconfig.conf

When a config file is passed via config parameter, it will override any configuration that may have left upon lab destroy.

With such topology file containerlab is instructed to take a file myconfig.conf from the current working directory, copy it to the lab directory for that specific node under the /flash/startup-config name and mount that dir to the container. This will result in this config to act as a startup config for the node.

It is possible to change the default config which every ceos node will start with with the following steps:

1. Save the default configuration template under some local file name² and add the necessary changes to it
2. Use this file as a startup-config for ceos kind:

   name: ceos
   
   topology:
   kinds:
       ceos:
       startup-config: ceos-custom-startup.cfg
   nodes:
       # ceos1 will boot with ceos-custom-startup.cfg as set in the kind parameters
       ceos1:
       kind: ceos
       image: ceos:4.25.0F
       # ceos2 will boot with its own specific startup config, as it overrides the kind variables
       ceos2: 
       kind: ceos
       image: ceos:4.25.0F
       startup-config: node-specific-startup.cfg
   links:
       - endpoints: ["ceos1:eth1", "ceos2:eth1"]
   

Configuration persistency#

It is important to understand how configuration persistency behaves when a single lab is going through rounds of deploy->destroy actions.

When the lab with cEOS nodes gets deployed for the first time the configuration file is generated with the IPv4/6 address assigned to Ma0 management interface. These management interface addresses match the IP addresses that docker has assigned to cEOS containers. This makes it possible to have the cEOS nodes to start up with Management interface already correctly addressed.

When a user later configures the nodes during the lab exercise and saves it with wr mem or similar, the changes will be written to startup-config file of cEOS.

User then may destroy the lab and the config changes will persist on disk, this is done with destroy command. During this operation the containers will be destroyed, but their configuration files will still be kept in the lab directory by the path clab-$labName.

If a user then desires to start this lab once again it may lead to a problem. Since docker may assign new IP addresses to the cEOS nodes of the lab, the configuration saved on disk may not match those new docker-assigned addresses, and that will result in an incorrect management interface configuration.

To avoid this, and be able to start the nodes with the previously saved configuration, users may do the following:

1. Address the nodes explicitly via user defined addresses. This will instruct docker to use the addresses as specified by a user in a clab file.
2. Leverage user defined config, if all you need is to have a startup config.

Saving configuration#

In addition to cli commands such as write memory user can take advantage of the containerlab save command. It saves running cEOS configuration into a file by conf-saved.conf path in the relevant node directory.

Container configuration#

To start an Arista cEOS node containerlab uses the configuration instructions described in Arista Forums¹. The exact parameters are outlined below.

File mounts#

When a user starts a lab, containerlab creates a node directory for storing configuration artifacts. For ceos kind containerlab creates flash directory for each ceos node and mounts these folders by /mnt/flash paths.

❯ tree clab-srlceos01/ceos
clab-srlceos01/ceos
└── flash
    ├── AsuFastPktTransmit.log
    ├── debug
    │   └── proc
    │       └── modules
    ├── fastpkttx.backup
    ├── Fossil
    ├── kickstart-config
    ├── persist
    │   ├── local
    │   ├── messages
    │   ├── persistentRestartLog
    │   ├── secure
    │   └── sys
    ├── schedule
    │   └── tech-support
    │       └── ceos_tech-support_2021-01-14.0907.log.gz
    ├── SsuRestoreLegacy.log
    ├── SsuRestore.log
    ├── system_mac_address
    └── startup-config

9 directories, 11 files

Lab examples#

The following labs feature cEOS node:

• SR Linux and cEOS

Known issues or limitations#

cgroups v1#

As of this writing (22-June, 2021), ceos-lab image requires a cgroups v1 environment. For many users this should not require any changes to the runtime environment. However, some linux distributions (ref: #467) may be configured to use cgroups v2 out-of-the-box, which will prevent ceos-lab image from booting. In such cases, the users will need to configure their system to utilize a cgroups v1 environment.

Consult your distribution's documentation for details regarding configuring cgroups v1 in case you see similar startup issues as indicated in #467.