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Almost all IP hosts assume that other IP hosts accept datagrams that are at
least 576 bytes long (see RFC 791 for more information on length of
datagrams). If any line used by AS/400 TCP/IP is configured to allow less than
576 bytes, any hosts that transmit to the AS/400 system using that line should
be configured to send datagrams that are less than or equal to 576 bytes;
otherwise, data may be lost.
4. There are additional parameters on the PING command that allow you to
specify the packet length, the number of packets to be sent, and the wait time
for a response. The default wait time of 1 second allows the remote system
enough time to respond in most networks. However, if the remote system is far
away or if the network is busy, increasing the wait time parameter can give a
successful result.
It is recommended that the parameter values be left at their default values. Be
aware that if you do change them, a combination of large packet length and
short wait time may not give the network enough time to transmit and receive
the response, and time-outs can occur. If the network is not given enough time
to transmit and receive the response, it can appear that you do not have
connectivity to a system when, in fact, you actually do.
5. If a remote system fails to respond, it may mean that the system, network,
gateway, router, or bridge in the network is unavailable or not working. Failure to
respond can also mean that the remote system does not put into effect the
ICMP echo request protocol. Try verifying the connection to other systems and
between those other systems to determine where the failure is most likely
located.
6. If a remote system fails to respond when you are using the PING command to
verify an interface, which is configured to a line description of Ethernet type,
make sure the correct Ethernet standard or *ALL is specified in the Ethernet line
description.
7. Failure to get responses from all systems in a network indicates the trouble is
somewhere along the path. Verify the connection to the gateway leading into the
network in question. If this fails, work back from the remote system you cannot
reach until you find the point of failure.
8. Packets are sent using a low-level protocol that does not guarantee delivery.
Because an echo request may be lost, do not assume that a network or
gateway has failed until several commands fail to get beyond a point in the
path.
Cause List C
1. Check the AS/400 QSYSWRK subsystem for all necessary jobs (local or
remote). There should be at least the QTCPIP job. It is a control job. There
should also be at least one job for each of the applications you are attempting
to use as shown in Figure 248 on page 435. It is possible that these jobs may
not be named identically to your subsystem jobs for the FTP, LPD, and TELNET
jobs. All FTP jobs begin with QTFTP. All LPD jobs begin with QTLPD. All TELNET
jobs will be named QTVTELNET and QTVDEVICE. It is possible to have more than
one FTP, LPD, or TELNET server jobs. All SMTP jobs begin with QTSMTP. SMTP
has up to four jobs active in the QSYSWRK subsystem and two jobs active in
the QSNADS subsystem. All SNMP jobs begin with QTMSNMP. SNMP can have
three jobs active in the QSYSWRK subsystem, QTMSNMP, QTMSNMPRCV,
and QSNMPSA.
Use the Work with Active Jobs (WRKACTJOB) command to display these jobs.
Type WRKACTJOB SBS(QSYSWRK).
434 OS/400 TCP/IP Configuration and Reference V4R4
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