C:\> ipconfig/release
Windows IP Configuration
No operation can be performed on Ethernet while it has its media disconnected.
Ethernet adapter Ethernet:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Wireless LAN adapter Wi-Fi:
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::a1cc:4239:d3ab:2675%6
Default Gateway . . . . . . . . . :
C:\> ipconfig/renew
Windows IP Configuration
No operation can be performed on Ethernet while it has its media disconnected.
Ethernet adapter Ethernet:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Wireless LAN adapter Wi-Fi:
Connection-specific DNS Suffix . : lan
Link-local IPv6 Address . . . . . : fe80::a1cc:4239:d3ab:2675%6
IPv4 Address. . . . . . . . . . . : 10.10.10.130
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.10.10.1
C:\>
If, after releasing the IP configuration, the host is unable to obtain fresh information from the DHCP server, it could be that there is no network connectivity. In this case, you verify that the NIC has an illuminated link light, indicating that it has a physical connection to the network. If this does not solve the problem, the DHCP server or network connections to the DHCP server may be the issue.
Packet Tracer—Use the ipconfig Command (20.3.3)
In this activity, you will use the ipconfig command to examine IP configuration information on a host.
The ping Command (20.3.4)
Probably the most commonly used network utility is ping. Most IP-enabled devices support some form of the ping command to test whether network devices can be reached through the IP network.
If the IP configuration appears to be correctly configured on the local host, next, you can test network connectivity by using ping. The ping command can be followed by either an IP address or the name of a destination host. In Example 20-4, the user pings the default gateway at 10.10.10.1 and then pings www.cisco.com.
Example 20-4 The ping Command
C:\>
ping 10.10.10.1
Pinging 10.10.10.1 with 32 bytes of data:
Reply from 10.10.10.1: bytes=32 time=1ms TTL=64
Reply from 10.10.10.1: bytes=32 time=1ms TTL=64
Reply from 10.10.10.1: bytes=32 time=1ms TTL=64
Reply from 10.10.10.1: bytes=32 time=1ms TTL=64
Ping statistics for 10.10.10.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 1ms, Average = 1ms
C:\>
ping www.cisco.com
Pinging e2867.dsca.akamaiedge.net [104.112.72.241] with 32 bytes of data:
Reply from 104.112.72.241: bytes=32 time=25ms TTL=53
Reply from 104.112.72.241: bytes=32 time=25ms TTL=53
Reply from 104.112.72.241: bytes=32 time=27ms TTL=53
Reply from 104.112.72.241: bytes=32 time=24ms TTL=53
Ping statistics for 104.112.72.241:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 24ms, Maximum = 27ms, Average = 25ms
C:\>
When a ping is sent to an IP address, a packet known as an echo request is sent across the network to the IP address specified. If the destination host receives the echo request, it responds with a packet known as an echo reply. If the source receives the echo reply, connectivity is verified by the reply from the specific IP address. The ping is not successful if a message such as request timed out or general failure appears.
If a ping command is sent to a name, such as www.cisco.com, a packet is first sent to a DNS server to resolve the name to an IP address. After the IP address is obtained, the echo request is forwarded to the IP address and the process proceeds. If a ping to the IP address succeeds but a ping to the name does not, there is most likely a problem with DNS.
Ping Results (20.3.5)
If ping commands to both the name and IP address are successful but the user is still unable to access the application, the problem most likely resides in the application on the destination host. For example, the requested service might not be running.
If neither ping is successful, network connectivity along the path to the destination is most likely the problem. If this occurs, it is common practice to ping the default gateway. If the ping to the default gateway is successful, the problem is not local. If the ping to the default gateway fails, the problem resides on the local network.
In some cases, the ping may fail, but network connectivity is not the problem. A ping may fail due to the firewall on the sending or receiving device, or a router along the path that is blocking the pings.
The basic ping command usually issues four echoes and waits for the replies to each one. It can, however, be modified to increase its usefulness. The options listed in Example 20-5 display additional features available.
Example 20-5 Options for the ping Command
C:\>
ping
Usage: ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS]
[-r count] [-s count] [[-j host-list] | [-k host-list]]
[-w timeout] [-R] [-S srcaddr] [-c compartment] [-p]
[-4] [-6] target_name
Options:
-t Ping the specified host until stopped.
To see statistics and continue – type Control-Break;
To stop – type Control-C.
-a Resolve addresses to hostnames.
-n count Number of echo requests to send.
-l size Send buffer size.
-f Set Don’t Fragment flag in packet (IPv4-only).
-i TTL Time To Live.
-v TOS Type Of Service (IPv4-only. This setting has been deprecated
and has no effect on the type of service field in the IP
Header).
-r count Record route for count hops (IPv4-only).
-s count Timestamp for count hops (IPv4-only).
-j host-list Loose source route along host-list (IPv4-only).
-k host-list Strict source route along host-list (IPv4-only).
-w timeout Timeout in milliseconds to wait for each reply.
-R Use routing header to test reverse route also (IPv6-only).
Per RFC 5095 the use of this routing header has been
deprecated. Some systems may drop echo requests if
this header is used.
-S srcaddr Source address to use.
-c compartment Routing compartment identifier.
-p Ping a Hyper-V Network Virtualization provider address.
-4 Force using IPv4.
-6 Force using IPv6.
C:\>
Packet Tracer—Use the ping Command (20.3.6)
In this activity, you will use the ping command to examine end-to-end connectivity between hosts.
Divide and Conquer with ping (20.3.7)
Connectivity problems occur on wireless networks, wired networks, and networks that use both. When you‛re troubleshooting a network with both wired and wireless connections, it is often best to troubleshoot using a divide-and-conquer technique to isolate the problem to either the wired or wireless network. The easiest way to determine if the problem is with the wired or wireless network is to do the following:
- Ping from a wireless client to the default gateway. This verifies whether the wireless client is connecting as expected.
- Ping from a wired client to the default gateway. This verifies whether the wired client is connecting as expected.
- Ping from the wireless client to a wired client. This verifies whether the wireless router is functioning as expected.