The ip command (iproute2) and virtual interfaces

I've never quite gotten the hang of using "ip" in place of ifconfig, but this blog post shows how to do several things I have wondered about.
The main thing I was looking for was how to add and delete a virtual interface which required some additional research.

The not at all obvious way to get help on this is:
# ip link add help
or
# man ip-link

Show status of interfaces

# ip ad
<... snipped loopback stuff ...>
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 5c:26:0a:2b:29:54 brd ff:ff:ff:ff:ff:ff
    inet 64.112.251.9/21 brd 64.112.255.255 scope global eno1
    inet6 fe80::5e26:aff:fe2b:2954/64 scope link
       valid_lft forever preferred_lft forever

Add a virtual interface

# ip link add type veth
# ip ad
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 5c:26:0a:2b:29:54 brd ff:ff:ff:ff:ff:ff
    inet 64.112.251.9/21 brd 64.112.255.255 scope global eno1
    inet6 fe80::5e26:aff:fe2b:2954/64 scope link
       valid_lft forever preferred_lft forever
17: veth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 9e:59:c1:cc:3a:e3 brd ff:ff:ff:ff:ff:ff
18: veth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 2e:5e:c1:b0:71:44 brd ff:ff:ff:ff:ff:ff

For some reason, it always adds two interfaces.

Set address for a virtual interface

# ip addr add 10.1.2.3/8 dev veth0
# ip ad
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 5c:26:0a:2b:29:54 brd ff:ff:ff:ff:ff:ff
    inet 64.112.251.9/21 brd 64.112.255.255 scope global eno1
    inet6 fe80::5e26:aff:fe2b:2954/64 scope link
       valid_lft forever preferred_lft forever
17: veth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 02:d1:8f:79:fe:db brd ff:ff:ff:ff:ff:ff
    inet 10.1.2.3/8 scope global veth0
18: veth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether ee:84:34:2c:ce:bc brd ff:ff:ff:ff:ff:ff
The link is still in the "down" state, and can't be used yet.

Set status of virtual interface to "up"

# ip link set up dev veth0
# ip ad
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 5c:26:0a:2b:29:54 brd ff:ff:ff:ff:ff:ff
    inet 64.112.251.9/21 brd 64.112.255.255 scope global eno1
    inet6 fe80::5e26:aff:fe2b:2954/64 scope link
       valid_lft forever preferred_lft forever
17: veth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN qlen 100
    link/ether 02:d1:8f:79:fe:db brd ff:ff:ff:ff:ff:ff
    inet 10.1.2.3/32 scope global veth0

Notice that the state is still listed as down, but ifconfig shows the same device with a state of up. Go figure.

# ifconfig veth0
veth0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 10.1.2.3  netmask 255.255.255.255  broadcast 0.0.0.0
        ether 02:d1:8f:79:fe:db  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

Remove virtual interface

# ip link delete dev veth0