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How to Display the Status of Transmissions
for Packets of a Specific Address Type
Use the -f option of the netstat command to view statistics related to packet transmissions of a particular address family.
View statistics for transmissions of either IPv4 or IPv6 packets.
$ netstat -f inet | inet6
To view IPv4 transmission information, type inet as the argument to netstat -f. Use inet6 as the argument to netstat -f to view IPv6 information.
Example 8-10 Status of IPv4 Packet Transmission
The following example shows output from the netstat -f inet command.
TCP: IPv4 Local Address Remote Address Swind Send-Q Rwind Recv-Q State -------------------- -------------------- ----- ------ ----- ------ ------- host58.734 host19.nfsd 49640 0 49640 0 ESTABLISHED host58.38063 host19.32782 49640 0 49640 0 CLOSE_WAIT host58.38146 host41.43601 49640 0 49640 0 ESTABLISHED host58.996 remote-host.login 49640 0 49206 0 ESTABLISHED |
Example 8-11 Status of IPv6 Packet Transmission
The following example shows output from the netstat -f inet6 command.
TCP: IPv6 Local Address Remote Address Swind Send-Q Rwind Recv-Q State If ------------------ ------------------------- ----- ------ ----- ------ --------- ----- localhost.38065 localhost.32792 49152 0 49152 0 ESTABLISHED localhost.32792 localhost.38065 49152 0 49152 0 ESTABLISHED localhost.38089 localhost.38057 49152 0 49152 0 ESTABLISHED |
How to Display the Status of Known Routes
The -r option of the netstat command displays the routing table for the local host. This table shows the status of all routes that the host knows about. You can run this option of netstat from your user account.
Example 8-12 Routing Table Output by the netstat Command
The following example shows output from the netstat -r command.
Routing Table: IPv4 Destination Gateway Flags Ref Use Interface -------------------- -------------------- ----- ----- ------ --------- host15 myhost U 1 31059 hme0 10.0.0.14 myhost U 1 0 hme0 default distantrouter UG 1 2 hme0 localhost localhost UH 42019361 lo0 Routing Table: IPv6 Destination/Mask Gateway Flags Ref Use If --------------------------- --------------------------- ----- --- ------ ----- 2002:0a00:3010:2::/64 2002:0a00:3010:2:1b2b:3c4c:5e6e:abcd U 1 0 hme0:1 fe80::/10 fe80::1a2b:3c4d:5e6f:12a2 U 1 23 hme0 ff00::/8 fe80::1a2b:3c4d:5e6f:12a2 U 1 0 hme0 default fe80::1a2b:3c4d:5e6f:12a2 UG 1 0 hme0 localhost localhost UH 9 21832 lo0 |
Parameter | Description |
|---|---|
Destination Destination/Mask | Specifies the host that is the destination endpoint of the route. Note that the IPv6 routing table shows the prefix for a 6to4 tunnel endpoint (2002:0a00:3010:2::/64) as the route destination endpoint. |
Gateway | Specifies the gateway to use for forwarding packets. |
Flags | Indicates the current status of the route. The U flag indicates that the route is up. The G flag indicates that the route is to a gateway. |
Use | Shows the number of packets sent. |
Interface | Indicates the particular interface on the local host that is the source endpoint of the transmission. |
Probing Remote Hosts With the ping Command
You can use the ping command to determine the status of a remote host. When you run ping, the ICMP protocol sends a datagram to the host that you specify, asking for a response. ICMP is the protocol responsible for error handling on a TCP/IP network. When you use ping, you can find out whether an IP connection exists for the specified remote host.
The following is the basic syntax of ping:
/usr/sbin/ping host [timeout]
In this syntax, host is the name of the remote host. The optional timeout argument indicates the time in seconds for the ping command to continue trying to reach the remote host. The default is 20 seconds. For additional syntax and options, refer to the ping(1M) man page.
How to Determine if a Remote Host Is
Running
Type the following form of the ping command:
$ ping hostname
If host hostname is accepting ICMP transmissions, this message is displayed:
hostname is alive
This message indicates that hostname responded to the ICMP request. However, if hostname is down or cannot receive the ICMP packets, you receive the following response from the ping command:
no answer from hostname
How to Determine if a Host Is Dropping
Packets
Use the -s option of the ping command to determine if a remote host is running but nevertheless losing packets.
Type the following form of the ping command:
$ ping -s hostname
Example 8-13 ping Output for Detecting Packet Dropping
The ping -s hostname command continually sends packets to the specified host until you send an interrupt character or a time out occurs. The responses on your screen resemble the following:
& ping -s host1.domain8 PING host1.domain8 : 56 data bytes 64 bytes from host1.domain8.COM (172.16.83.64): icmp_seq=0. time=1.67 ms 64 bytes from host1.domain8.COM (172.16.83.64): icmp_seq=1. time=1.02 ms 64 bytes from host1.domain8.COM (172.16.83.64): icmp_seq=2. time=0.986 ms 64 bytes from host1.domain8.COM (172.16.83.64): icmp_seq=3. time=0.921 ms 64 bytes from host1.domain8.COM (172.16.83.64): icmp_seq=4. time=1.16 ms 64 bytes from host1.domain8.COM (172.16.83.64): icmp_seq=5. time=1.00 ms 64 bytes from host1.domain8.COM (172.16.83.64): icmp_seq=5. time=1.980 ms ^C ----host1.domain8 PING Statistics---- 7 packets transmitted, 7 packets received, 0% packet loss round-trip (ms) min/avg/max/stddev = 0.921/1.11/1.67/0.26 |
The packet-loss statistic indicates whether the host has dropped packets. If ping fails, check the status of the network that is reported by the ifconfig and netstat commands. Refer to Monitoring the Interface Configuration With the ifconfig Command and Monitoring Network Status With the netstat Command.
Administering and Logging Network Status Displays
The following tasks show how to check the status of the network by using well-known networking commands.
How to Control the Display Output of
IP-Related Commands
You can control the output of the netstat and ifconfig commands to display IPv4 information only, or both IPv4 and IPv6 information.
Create the /etc/default/inet_type file.
Add one of the following entries to /etc/default/inet_type, as required for your network:
To display IPv4 information only:
DEFAULT_IP=IP_VERSION4
To display both IPv4 and IPv6 information:
DEFAULT_IP=BOTH
Or
DEFAULT_IP=IP_VERSION6
For more information about the inet_type file, see the inet_type(4) man page.
Note - The -4 and -6 flags in the ifconfig command override the values set in the inet_type file. The -f flag in the netstat command also overrides the values set in the inet_type file.
Example 8-14 Controlling Output to Select IPv4 and IPv6 Information
When you specify the DEFAULT_IP=BOTH or DEFAULT_IP=IP_VERSION6 variable in the inet_type file, you should have the following output:
% ifconfig -a lo0: flags=1000849 mtu 8232 index 1 inet 10.10.0.1 netmask ff000000 qfe0: flags=1000843 mtu 1500 index 2 inet 10.46.86.54 netmask ffffff00 broadcast 10.46.86.255 ether 8:0:20:56:a8 lo0: flags=2000849 mtu 8252 index 1 inet6 ::1/128 qfe0: flags=2000841 mtu 1500 index 2 ether 8:0:20:56:a8 inet6 fe80::a00:fe73:56a8/10 qfe0:1: flags=2080841 mtu 1500 index 2 inet6 2001:db8:3c4d:5:a00:fe73:56a8/64When you specify the DEFAULT_IP=IP_VERSION4 or DEFAULT_IP=IP_VERSION6 variable in the inet_type file, you should have the following output:
% ifconfig -a lo0: flags=849 mtu 8232 inet 10.10.0.1 netmask ff000000 qfe0: flags=843 mtu 1500 inet 10.46.86.54 netmask ffffff00 broadcast 10.46.86.255 ether 8:0:20:56:a8