2. Network Devices on master

The master nodes have multiple network ports. For our setup, one of them will be used for internet/outside access, another will be configured for the management network, which is used to control compute nodes with IPMI. And a third one port will be connected to the cluster network, used for SSH, network booting and data transfer.

Note

Log in to the master node assigned to you

[user@hostname ~]$ ssh root@<ip_address>
[root@master ~]#

The root password is orca2026.

2.1. Identify your available network devices

The ip link command will show you all available network devices and their state.

Note

The interface names are assigned automatically by systemd, and therefore they might be different on your system. For further information about the naming scheme, please follow this link.

[root@master ~]# ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 7c:c2:55:ed:29:d0 brd ff:ff:ff:ff:ff:ff
    altname enp2s0
    altname enx7cc255ed29d0
3: eno2: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 7c:c2:55:ed:29:d1 brd ff:ff:ff:ff:ff:ff
    altname enp5s0
    altname enx7cc255ed29d1
4: eno3: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 7c:c2:55:ed:29:d2 brd ff:ff:ff:ff:ff:ff
    altname enp6s0
    altname enx7cc255ed29d2
5: eno4: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 7c:c2:55:ed:29:d3 brd ff:ff:ff:ff:ff:ff
    altname enp7s0
    altname enx7cc255ed29d3

Danger

Do not change anything on eno1. This is the network connection that allows you to access the master node remotely! Use eno2 and eno3 for the management and cluster network.

Network	Interface
Internet	eno1
Management (IPMI)	eno2
Cluster (SSH)	eno3

You can change the state of an interface with the ip link set command.

[root@master ~]# ip link set eno2 down
[root@master ~]# ip link
...
3: eno2: <BROADCAST,MULTICAST> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
...
[root@master ~]# ip link set eno2 up
[root@master ~]# ip link
...
3: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
...

To get more details about your connection, you can use the ethtool command:

[root@master ~]# ethtool eno2
Settings for eno2:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supported pause frame use: Symmetric
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Advertised pause frame use: Symmetric
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Speed: 1000Mb/s
        Duplex: Full
        Auto-negotiation: on
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        MDI-X: on (auto)
        Supports Wake-on: pumbg
        Wake-on: g
        Current message level: 0x00000007 (7)
                            drv probe link
        Link detected: yes

It will report if it can find a physical link and what transfer rate it supports. In the above example you can see that the connection is running with 1000Mb/s or 1Gb/s.

Having a link does not give you an IP. You either have to request one via DHCP or set it statically.

Our first network device will be connected to the outside world and will get its IP via DHCP. The other two interfaces are connected to isolated networks, for which we will have to set static IPs.