Linux Network Bridge (refs)

Net­work and Se­cu­ri­ty

Lin­ux Serv­er

Vir­tu­al Ma­chines

Ref­er­ences

• Red Hat Blog: How to set up a net­work bridge for vir­tu­al ma­chine com­mu­ni­ca­tion (Net­work­Man­ag­er and nm­tui)
• Red Hat Docs: Red Hat > [9] > Con­fig­ur­ing and man­ag­ing net­work­ing > Chap­ter 4. Us­ing nm­tui to man­age net­work con­nec­tions us­ing a text-based in­ter­face
• Heiko's Blog: De­fine a net­work bridge us­ing Ubuntu’s / Lin­ux Mint's / Kali Lin­ux's Net­work­Man­ag­er GUI ap­pli­ca­tion
• Net­plain: Net­plan con­fig­u­ra­tion ex­am­ples
• Fabi­an Lee: KVM: Cre­at­ing a bridged net­work with Net­plan on Ubun­tu bion­ic
• Lin­ux­Techi: How to In­stall KVM on Ubun­tu 20.04 LTS Serv­er (Net­plan bridge)
• Ask Ubun­tu: Net­plan vs Net­work­Man­ag­er on Ubun­tu 18.04 and above
• Arch Lin­ux Wi­ki: Net­work bridge

Cre­ate Net­work Bridge by Net­plain on Ubun­tu Serv­er

Use the the com­mands ip, if­con­fig or net­workctl to get the list of the avail­able net­work adapters. Here we will cre­ate a bridge for eno2 which is the sec­ond net­work adapter of the phys­i­cal serv­er.

ifconfig -a

#Out­put

docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.17.0.1  netmask 255.255.0.0  broadcast 172.17.255.255
        inet6 fe80::42:c6ff:fe17:93db  prefixlen 64  scopeid 0x20<link>
        ether 02:42:c6:17:93:db  txqueuelen 0  (Ethernet)
        RX packets 1625  bytes 108954 (108.9 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1888  bytes 5226160 (5.2 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eno1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.16.1.201  netmask 255.255.255.0  broadcast 172.16.1.255
        inet6 fe80::72e2:84ff:fe13:8e6e  prefixlen 64  scopeid 0x20<link>
        ether 70:e2:84:13:8e:6e  txqueuelen 1000  (Ethernet)
        RX packets 16825485  bytes 23665075680 (23.6 GB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 3451343  bytes 333386187 (333.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0xfb300000-fb37ffff

eno2: flags=4098<BROADCAST,MULTICAST>  mtu 1500
        ether 70:e2:84:13:8e:6f  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0xfb200000-fb27ffff

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 131995267  bytes 12281222578 (12.2 GB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 131995267  bytes 12281222578 (12.2 GB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

veth26b9b17: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::78a9:8cff:fe0b:8cd  prefixlen 64  scopeid 0x20<link>
        ether 7a:a9:8c:0b:08:cd  txqueuelen 0  (Ethernet)
        RX packets 1625  bytes 131704 (131.7 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1915  bytes 5228146 (5.2 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ip address

#Out­put

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 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 70:e2:84:13:8e:6e brd ff:ff:ff:ff:ff:ff
    inet 172.16.1.201/24 brd 172.16.1.255 scope global eno1
       valid_lft forever preferred_lft forever
    inet6 fe80::72e2:84ff:fe13:8e6e/64 scope link
       valid_lft forever preferred_lft forever
4: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
    link/ether 02:42:c6:17:93:db brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:c6ff:fe17:93db/64 scope link
       valid_lft forever preferred_lft forever
6: veth26b9b17@if5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP group default
    link/ether 7a:a9:8c:0b:08:cd brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet6 fe80::78a9:8cff:fe0b:8cd/64 scope link
       valid_lft forever preferred_lft forever
9: eno2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 70:e2:84:13:8e:6f brd ff:ff:ff:ff:ff:ff

networkctl

#Out­put

IDX LINK        TYPE     OPERATIONAL SETUP
  1 lo          loopback carrier     unmanaged
  2 eno1        ether    routable    configured
  4 docker0     bridge   routable    unmanaged
  6 veth26b9b17 ether    degraded    unmanaged
  9 eno2        ether    off         unmanaged

5 links listed.

Now we are go­ing to ed­it Netplains's con­fig­u­ra­tion. Note the con­fig­u­ra­tion file may have dif­fer­ent name with­in your dis­tri­b­u­tion.

sudo nano /etc/netplan/00-installer-config.yaml  # cat /etc/netplan/00-installer-config.yaml

#Ap­ply

# This is the network config written by 'subiquity'
network:
  version: 2
  ethernets:
    eno1:
      dhcp4: true
      #addresses: [172.16.1.201/24]
      #gateway4: 172.16.1.1
      #nameservers:
      #  addresses: [172.16.1.1, 8.8.8.8, 8.8.4.4]
      dhcp6: no
    eno2:
      dhcp4: no
      dhcp6: no
  bridges:
      br0:
        interfaces: [eno2]
        addresses: [172.16.1.205/24]
        gateway4: 172.16.1.1
        nameservers:
          addresses: [172.16.1.1, 8.8.8.8, 8.8.4.4]

Ap­ply the new net­work con­fig­u­ra­tion and check the re­sult.

sudo netplan apply

networkctl

#Out­put

IDX LINK        TYPE     OPERATIONAL SETUP
  1 lo          loopback carrier     unmanaged
  2 eno1        ether    routable    configured
  4 docker0     bridge   routable    unmanaged
  6 veth26b9b17 ether    degraded    unmanaged
  9 eno2        ether    carrier     configured
 10 br0         bridge   routable    configured

6 links listed.

networkctl status br0

#Out­put

● 10: br0
               Link File: /usr/lib/systemd/network/99-default.link
            Network File: /run/systemd/network/10-netplan-br0.network
                    Type: bridge
                   State: routable (configured)
                  Driver: bridge
              HW Address: 70:e2:84:13:8e:6f (Wistron Infocomm (Zhongshan) Corporation)
                     MTU: 1500 (min: 68, max: 65535)
           Forward Delay: 15s
              Hello Time: 2s
                 Max Age: 20s
             Ageing Time: 5min
                Priority: 32768
                     STP: no
  Multicast IGMP Version: 2
    Queue Length (Tx/Rx): 1/1
                 Address: 172.16.1.205
                          fe80::70be:baff:fed1:2d93
                 Gateway: 172.16.1.1 (TP-LINK TECHNOLOGIES CO.,LTD.)
                     DNS: 172.16.1.1
                          8.8.8.8
                          8.8.4.4
       Activation Policy: up

ip a show br0 && ip a show eno2

#Out­put

10: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 70:e2:84:13:8e:6f brd ff:ff:ff:ff:ff:ff
    inet 172.16.1.205/24 brd 172.16.1.255 scope global br0
       valid_lft forever preferred_lft forever
    inet6 fe80::70be:baff:fed1:2d93/64 scope link
       valid_lft forever preferred_lft forever
9: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master br0 state UP group default qlen 1000
    link/ether 70:e2:84:13:8e:6f brd ff:ff:ff:ff:ff:ff

ifconfig br0 && ifconfig eno2

#Out­put

br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.16.1.205  netmask 255.255.255.0  broadcast 172.16.1.255
        inet6 fe80::70be:baff:fed1:2d93  prefixlen 64  scopeid 0x20<link>
        ether 70:e2:84:13:8e:6f  txqueuelen 1000  (Ethernet)
        RX packets 7935  bytes 3090030 (3.0 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 11575  bytes 11225034 (11.2 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eno2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether 70:e2:84:13:8e:6f  txqueuelen 1000  (Ethernet)
        RX packets 9115  bytes 3543374 (3.5 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 16426  bytes 11489692 (11.4 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0xfb200000-fb27ffff

Reg­is­ter: Net­work and Se­cu­ri­ty

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