1.10 Verify IP parameters for Client OS (Windows, Mac OS, Linux)

Network engineers spend a lot of time proving that “the network is fine” by checking the client. This objective asks you to know the commands that display a host’s IP address, subnet mask, default gateway, DNS servers, MAC address, and routing table on the three major operating systems, and how to interpret them. The four parameters a host needs to communicate fully are:

Parameter	Purpose	Symptom if wrong
IP address	Identifies the host	169.254.x.x means DHCP failed; duplicate causes intermittent loss
Subnet mask / prefix	Tells the host who is local	Wrong mask: some local hosts unreachable, or gateway “not on subnet”
Default gateway	Router for non-local traffic	Local LAN works, nothing beyond it
DNS server	Resolves names to addresses	`ping 8.8.8.8` works, `ping google.com` fails

Windows

The core command is ipconfig. On its own it shows address, mask, and gateway for each adapter; ipconfig /all adds MAC address, DHCP server, lease times, and DNS servers.

C:\> ipconfig /all

Windows IP Configuration
   Host Name . . . . . . . . . . . . : LAPTOP-SALES01
   Primary Dns Suffix  . . . . . . . : corp.example.com
   Node Type . . . . . . . . . . . . : Hybrid

Ethernet adapter Ethernet0:
   Connection-specific DNS Suffix  . : corp.example.com
   Description . . . . . . . . . . . : Intel(R) Ethernet Connection I219-LM
   Physical Address. . . . . . . . . : 00-50-56-BE-1A-2B
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   IPv6 Address. . . . . . . . . . . : 2001:db8:acad:1:9c1e:44b7:2a10:f0d3
   Link-local IPv6 Address . . . . . : fe80::9c1e:44b7:2a10:f0d3%12
   IPv4 Address. . . . . . . . . . . : 192.168.5.20(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.128
   Lease Obtained. . . . . . . . . . : Monday, September 7, 2026 08:12:03
   Lease Expires . . . . . . . . . . : Tuesday, September 8, 2026 08:12:03
   Default Gateway . . . . . . . . . : fe80::1%12
                                       192.168.5.1
   DHCP Server . . . . . . . . . . . : 192.168.5.1
   DNS Servers . . . . . . . . . . . : 192.168.5.5
                                       8.8.8.8

Things to notice: the physical (MAC) address uses hyphens; the %12 after the IPv6 link-local addresses is the zone ID (interface index) Windows needs to know which interface a link-local address belongs to; the IPv6 default gateway is the router’s link-local address, learned from an RA; and the DHCP server, lease times, and DNS servers are only visible with /all.

Other Windows commands:

Command	Purpose
`ipconfig /release` and `ipconfig /renew`	Give up and re-request the DHCP lease
`ipconfig /flushdns` and `ipconfig /displaydns`	Clear or show the DNS resolver cache
`route print` or `netstat -rn`	Show the host routing table (default route appears as 0.0.0.0 mask 0.0.0.0)
`arp -a`	Show the ARP cache (IP-to-MAC)
`netstat -an`	Show open ports and connections
`nslookup example.com`	Query DNS
`ping`, `tracert`, `pathping`	Test reachability and path
`getmac`	Show MAC addresses only

macOS

macOS is built on BSD Unix, so it uses the classic Unix ifconfig and netstat commands, plus the Apple-specific networksetup tool. The System Settings GUI (Network pane) shows the same information.

mac$ ifconfig en0
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        options=6463<RXCSUM,TXCSUM,TSO4,TSO6,CHANNEL_IO,PARTIAL_CSUM>
        ether 3c:22:fb:12:34:56
        inet6 fe80::1c2d:3e4f:5a6b:7c8d%en0 prefixlen 64 secured scopeid 0xc
        inet6 2001:db8:acad:1:8d3:9a1c:7f2e:1b44 prefixlen 64 autoconf secured
        inet 192.168.5.21 netmask 0xffffff80 broadcast 192.168.5.127
        media: autoselect
        status: active

Note that ifconfig shows the mask in hexadecimal: 0xffffff80 is 255.255.255.128, a /25. The ether line is the MAC address. ifconfig does not show the default gateway or DNS servers; use these instead:

Command	Purpose
`netstat -rn`	Routing table; the `default` line shows the gateway
`networksetup -listallnetworkservices`	List interfaces by name (Wi-Fi, Ethernet)
`networksetup -getinfo "Wi-Fi"`	IP, mask, router (gateway), and MAC for that service
`networksetup -getdnsservers "Wi-Fi"`	DNS servers for that service
`scutil --dns`	Full DNS resolver configuration
`arp -a`	ARP cache
`ipconfig getifaddr en0`	Just the IPv4 address (macOS `ipconfig` is unrelated to the Windows tool)
`sudo ipconfig set en0 DHCP`	Renew the DHCP lease

mac$ networksetup -getinfo "Wi-Fi"
DHCP Configuration
IP address: 192.168.5.21
Subnet mask: 255.255.255.128
Router: 192.168.5.1
Client ID:
IPv6: Automatic
IPv6 IP address: none
IPv6 Router: none
Wi-Fi ID: 3c:22:fb:12:34:56

mac$ netstat -rn
Routing tables

Internet:
Destination        Gateway            Flags           Netif Expire
default            192.168.5.1        UGScg             en0
127                127.0.0.1          UCS               lo0
127.0.0.1          127.0.0.1          UH                lo0
192.168.5.0/25     link#12            UCS               en0      !
192.168.5.1        a0:b1:c2:d3:e4:f5  UHLWIir           en0   1197

Linux

Modern Linux distributions use the ip command from the iproute2 package; the older ifconfig, route, and netstat commands from net-tools may not be installed by default but still work when present and appear on the exam.

linux$ ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
2: ens192: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP
    link/ether 00:0c:29:ab:cd:ef brd ff:ff:ff:ff:ff:ff
    inet 192.168.5.22/25 brd 192.168.5.127 scope global dynamic ens192
       valid_lft 85211sec preferred_lft 85211sec
    inet6 2001:db8:acad:1:20c:29ff:feab:cdef/64 scope global dynamic
    inet6 fe80::20c:29ff:feab:cdef/64 scope link

linux$ ip route
default via 192.168.5.1 dev ens192 proto dhcp metric 100
192.168.5.0/25 dev ens192 proto kernel scope link src 192.168.5.22

ip addr (abbreviated ip a) shows the mask as a prefix length (/25), the MAC as link/ether, and both IPv6 addresses. Notice the Linux host’s IPv6 addresses were built with EUI-64 (ff:fe in the middle, first byte 00 flipped to 02). ip route (or ip r) shows the default gateway on the default via line.

Command	Purpose
`ip addr` / `ip a`	Addresses, masks, MAC
`ip route` / `ip r`	Routing table and default gateway
`ip neigh`	ARP / neighbor cache
`ip -6 route` and `ip -6 neigh`	IPv6 equivalents
`ifconfig`	Legacy: addresses and MAC (net-tools)
`route -n` or `netstat -rn`	Legacy: routing table
`cat /etc/resolv.conf` or `resolvectl status`	DNS servers
`nmcli device show ens192`	Everything, on NetworkManager systems
`dhclient -r` then `dhclient`	Release and renew DHCP
`ping`, `traceroute`, `dig`, `nslookup`	Reachability and DNS testing