HP OpenVMS Systems Documentation

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Compaq TCP/IP Services for OpenVMS
Tuning and Troubleshooting

Previous Contents Index Using ping on a Multihomed Host

If you suspect one of the interfaces is down, you can test the interface by using:

  • The ping command on another system to ping the IP address of the suspect interface. Because TCP/IP Services sends messages via the first matching entry in the routing table, you might not be exercising the interface if you test on the local system.
  • The traceroute -s src_addr command on the local system. This command uses the IP address specified with the -s flag in outgoing probe packets. If the command fails, the error message may indicate that the problem is with the interface.

1.2.2 Checking the Network Interface Parameters

Use the ifconfig command to check the configuration of a network interface. A common problem is a misconfigured subnet mask or incorrect IP address. Be sure to check the values of these parameters.

To display configuration information for all interfaces, enter the following command:

TCPIP> ifconfig -a
     inet  netmask ff000000  ipmtu 4096
TN0: flags=80<NOARP>
     HWaddr aa:0:4:0:71:f8
     inet  netmask ffffff00 broadcast ipmtu 1500

For example, to display the configuration for interface WF0, enter the following command:

TCPIP> ifconfig WF0

The system displays the following information:

     inet netmask ffff0000 broadcast ipmtu 4470
     inet6 fe80::200:f8ff:febd:bc22
     inet6 3ffe:1200:4120:1000:200:f8ff:febd:bc22

The first line of this display shows the interface characteristics. The interface should be UP and RUNNING (exceptions to this are the LO0 and TN0 interfaces). The pertinent fields in this display show the interface's IP address, the subnet mask, the broadcast mask, and the maximum transmit unit.

You can also obtain information using the following commands:

Interface   IP_Addr         Network mask          Receive          Send     MTU

 LO0                 137           137    4096
 WE0            5089          4191    1500


 Interface: LO0
   IP_Addr:         NETWRK:         BRDCST:

 Interface: WE0
   IP_Addr:         NETWRK:     BRDCST:

If you are not familiar with IP addressing and the concepts of subnet and broadcast masks, review the information in DIGITAL TCP/IP Services for OpenVMS Concepts and Planning before proceeding with troubleshooting tasks.

1.2.3 Displaying and Modifying the Internet-to-Ethernet Translation Tables

Use the arp utility or the SHOW ARP management command to check the IP address to Ethernet address translation entries in the Address Resolution Protocol (ARP) table. This is useful if you think incorrect entries are being added to the ARP table. For example, if you enter a command and an unexpected host responds, you may have two systems defined with the same IP address in the ARP table.

To display entries in the ARP table, enter the following command:

Cnt  Flags    Timer Host                      Phys Addr
  1: UCS        451               08-00-2b-39-c7-ac
  2: UC           0              aa-00-04-00-8d-13
  3: UC           3              00-00-f8-45-a0-b4
  4: UC          14              00-00-f8-00-f7-41
  5: UC          50              00-d0-b7-19-78-a4
  6: UCS          9             00-50-8b-72-7f-ff
  7: UCS        150             00-50-8b-4d-91-b3

The following TCP/IP Services management commands allow you to configure the hardware addresses for remote IP addresses:

  • SET ARP allows you to add the hardware address to the ARP table.
  • SET PROTOCOL ARP allows you specify the time interval for ARP to hold information in its cache. Use the SET CONFIGURATION PROTOCOL ARP command to set this information in the permanent configuration database.

For more information about these procedures, refer to the Compaq TCP/IP Services for OpenVMS Management manual.

For information about using the arp utility, refer to Appendix A.

1.2.4 Examining Network Statistics

Use the netstat utility or the SHOW INTERFACE command to check interface and protocol statistics, per-connection status, and memory buffer use. Look for bad checksums, excessive retransmissions, dropped packets, out-of-order packets, and lost-carrier errors.

For example:

TCPIP> netstat -i
Name  Mtu   Network  Address               Ipkts Ierrs    Opkts Oerrs  Coll
TN0*  1280  Link     Link#2                    0     0        0     0     0
WF0   4470  Link     00:00:f8:cd:1e:e4  48855499     0  2035244     0     0
WF0   4470  16.20    ucxaxp             48855499     0  2035244     0     0
LO0   4096  Link     Link#1               165084     0   165084     0     0
LO0   4096  127      LOCALHOST            165084     0   165084     0     0

The netstat command displays information used to diagnose failures. Some problems to look for include:

  • Network problems
    If the netstat -i command shows an excessive number of input errors (Ierrs), output errors (Oerrs), or collisions (Coll), you may be experiencing a network problem, such as improperly connected cables or a saturated Ethernet.
  • Memory problems
    Use netstat -m to see whether the network is using an excessive amount of memory in proportion to the total amount of memory installed on the system.
    If several memory requests are delayed or denied, this means that your system was temporarily short of physical memory.
  • Network connections
    Use netstat -an to check allocated sockets (each socket results in a network connection).

1.2.5 Monitoring Network Traffic

The trace utility (TCPTRACE) is a tool you can use to trace packets going in and out of the system. To run the trace utility, enter the DCL command TCPTRACE. Use the qualifiers listed in the command reference section to customize tracing for your particular problem. For example:



The following sample is a TCPTRACE display:

TCPIP INTERnet trace RCV packet seq # = 1 at 23-OCT-1998 15:19:33.29

IP Version = 4,  IHL = 5,  TOS = 00,   Total Length = 217 = ^x00D9
IP Identifier  = ^x0065,  Flags (0=0,DF=0,MF=0),
      Fragment Offset = 0 = ^x0000,   Calculated Offset = 0 = ^x0000
IP TTL = 32 = ^x20,  Protocol = 17 = ^x11,  Header Checksum = ^x8F6C
IP Source Address      =
IP Destination Address =

UDP Source Port = 138,   UDP Destination Port = 138
UDP Header and Datagram Length = 197 = ^x00C5,   Checksum = ^x0E77

5DA81410   8F6C1120   00000065   D9000045    0000    E...awe.....l....]
         | 0E77C500   8A008A00 | FFFF1410    0010    ..........w.

For more information about using TCPTRACE, see Appendix A.

1.2.6 Checking Name Server Operation

After verifying that the underlying transport is working, check to see whether the remote host can be reached by its host name. If your name server resides on a remote system, make sure your resolver configuration specifies that system. To determine whether the resolver is pointing to the correct server, enter the following command:


BIND Resolver Parameters

 Local domain: lkg.dec.com


  State:     Started, Enabled

  Transport: UDP
  Domain:    lkg.dec.com
  Retry:     4
  Timeout:   4
  Servers:    rufus.lkg.dec.com, peach.lkg.dec.com
  Path:       lkg.dec.com


  State:     Enabled


Make sure the remote servers are reachable (using ping ) and that they are valid name servers.

If your name server resides on the local system, use the SHOW NAME_SERVICE command to make sure your resolver points to localhost .

Next, verify that the TCPIP$BIND process is enabled and running. First, enter the following command to determine whether TCPIP$BIND is enabled:


Service           Port  Proto    Process          Address            State

BIND                53  TCP,UDP  TCPIP$BIND             Enabled
DHCP                67  UDP      TCPIP$DHCP             Enabled
DIOSERVER         1451  TCP      CLM                 Disabled
ECHO                 7  TCP      MULTI               Disabled
ESNMP              705  UDP      ESNMP               Disabled
FINGER              79  TCP      TCPIP$FINGER             Enabled
FTP                 21  TCP      TCPIP$FTP             Enabled
HELLO            12345  TCP      HELLO_WORLD             Disabled
JOHN               520  UDP      UCX$ROUTER             Disabled
LBROKER           6570  UDP      TCPIP$LBROKER             Disabled
LPD                515  TCP      TCPIP$LPD             Enabled
MATT              5432  TCP      TCPIP$RLOGIN             Disabled
METRIC             570  UDP      TCPIP$METRIC             Enabled
MOUNT               10  TCP,UDP  TCPIP$MOUNTD             Enabled
NFS               2049  UDP      TCPIP$NFS             Enabled
NOTES             3333  TCP      NOTESRVR             Enabled
NTP                123  UDP      TCPIP$NTP             Enabled
PCNFS             5151  TCP,UDP  TCPIP$PCNFSD             Enabled
POP                110  TCP      TCPIP$POP             Enabled
PORTMAPPER         111  TCP,UDP  TCPIP$PORTM             Enabled
REXEC              512  TCP      TCPIP$REXEC             Enabled
RLOGIN             513  TCP      not defined             Enabled
RSH                514  TCP      TCPIP$RSH             Enabled
SMTP                25  TCP      TCPIP$SMTP             Enabled
SNMP               161  UDP      TCPIP$SNMP             Enabled
TELNET              23  TCP      not defined             Enabled
TFTP                69  UDP      TCPIP$TFTP             Enabled
XDM                177  UDP      TCPIP$XDM             Enabled

If the BIND process is enabled, it will appear in the display.

Then determine whether the BIND process is running by entering the following command:

OpenVMS V7.1-1H2  on node RUFUS   27-JUN-2000 16:45:46.84  Uptime  16 01:55:35
  Pid    Process Name    State  Pri      I/O       CPU       Page flts  Pages
2FC0021F TCPIP$NTP       LEF     10  2042786   0 00:02:03.43       657    190  N
2FC00221 TCPIP$LBROKER   LEF      9  3779921   0 00:06:27.51       652    271  N
2FC05046 TCPIP$POP_1     HIB     10   243688   0 00:00:48.42       955    598  N
2FC00289 TCPIP$PORTM     LEF     10    13289   0 00:00:03.23       614    189  N
2FC0628F TCPIP$RE_BG1879 LEF      6     1647   0 00:00:00.96      1709    612  N
2FC0089A NFS$SERVER      LEF     10    89284   0 00:00:19.28       978    580  N
2FC06C9E NOTES$00CD_2*   HIB      6   208844   0 00:01:22.65      1932    152  N
2FC03EC7 TCPIP$BIND_1    LEF     10   515297   0 00:01:26.06       972    322  N
2FC01CF6 TCPIP$PCNFSD    LEF     10      326   0 00:00:00.27       660    228  N

If the TCPIP$BIND_1 process is not running, look for errors in the SYS$SPECIFIC:[TCPIP$BIND]TCPIP$BIND_RUN.LOG file.

To reduce the possibility of a name server being unavailable, you might configure more than one name server on your network. This way, if the primary name server is unreachable or unresponsive, the resolver can query the other name server.

1.2.7 Checking the Route to a Remote Host

If you receive "network unreachable" messages, you may be experiencing a routing problem. You can easily detect whether the problem is with your local routing table by doing the following:

  • Enter a netstat -rn or SHOW ROUTE command.
    Display the routing table, then compare the output to the routing table of a properly running system. Make sure there is a default route defined and that the IP address listed in the gateway column for the default route and the local host are in the same subnet. The default route specifies the gateway to use when a route is not explicitly defined for the destination IP address.
    For example, enter the following command:

    TCPIP> netstat -rn
    Routing tables
    Destination      Gateway            Flags     Refs     Use Interface
    Route Tree for Protocol Family 2
    default        UG         17  1526068  WE0
    10.10/16      UGS         0   204911  WE0
    10.10.39/25         U           2    17942  BE0
    16.20/16      U          45  6219676  WE0
    16.20/16      U           0        0  WE0          UH          1    69844  LO0
    Route Tree for Protocol Family 26
    ::1              Link#1             UH          0        0  LO0
    ff01::/16        Link#1             U           0        0  LO0
  • To display a default route using the TCP/IP Services management commands, enter one of the following commands:


    The following example shows typical output from these two commands:

    Type           Destination                           Gateway
    PN                                    rufus.lkg.dec.com
    Type           Destination                           Gateway

    To set a default route, enter a command similar to the following:


    You can also set a default route by running the TCPIP$CONFIG procedure and selecting option 1 for Core, and then option 3 for Routing. TCPIP$CONFIG prompts with:

    * Do you want to configure dynamic ROUTED or GATED routing [NO]:

    Take the default value by pressing the Enter key. TCPIP$CONFIG then displays the current configuration and asks whether you want to reconfigure a default route:

    The current configuration for the default route is:
    Type           Destination                           Gateway
    PN                                    rufus.lkg.dec.com
    * Do you want to reconfigure a default route [YES]:
    Enter the Default Gateway host name []:
  • Next, use ping to see whether you can reach the routing gateway.

1.2.8 Checking the Routes Known to a Gateway

The traceroute command helps you locate problems between the local host and the remote destination by tracing the route of UDP packets from the local host to a remote host. Tracing attempts to determine the name and IP address of each gateway along the route to the remote host.

The traceroute command works by sending UDP packets with small time-to-live (TTL) values and an invalid port number to the remote system. The TTL values increase in increments of one for each group of three UDP packets sent. When a gateway receives a packet, it decrements the TTL. If the TTL is zero, the packet is not forwarded, and an ICMP "time exceeded" message is returned.

Intermediate gateways are detected when they return an ICMP "time exceeded" message. When traceroute receives an "invalid port" message, it knows that it reached the remote destination. ( traceroute operates by intentionally using an invalid port.) When traceroute receives this message, it knows it has reached the destination host and terminates the trace. In this way, traceroute develops a list of gateways starting at one hop away, and increasing one hop at a time until the remote host is reached.

For more information about using traceroute , see Appendix A.

1.2.9 Determine Whether Network Services Are Available

The auxiliary server functions like the UNIX internet daemon ( inetd ) by managing access to the network services. The auxiliary server assigns standard port numbers to services such as the BOOTP, SMTP, or FTP servers, and starts the appropriate image after receiving an incoming request.

To verify correct operation of a service, you need to verify that the service:

  • Has an entry in the service database
  • Has the correct attributes defined
  • Account has the correct privileges
  • Is enabled
  • Is started Displaying the Service Database

To display the services database, enter the SHOW SERVICE command. For example:

  (1)                 (2)    (3)         (4)              (5)                 (6)
Service             Port  Proto    Process          Address            State

FINGER                79  TCP      TCPIP$FINGER             Disabled
FTP                   21  TCP      TCPIP$FTP             Enabled
LPD                  515  TCP      TCPIP$LPD             Enabled
MOUNT                 10  UDP      TCPIP$NFS_M             Enabled
NFS                 2049  UDP      TCPIP$NFS             Enabled
NTP                  123  UDP      TCPIP$NTP             Enabled
PCNFS               5151  TCP,UDP  TCPIP$PCNFSD             Enabled
POP                  110  TCP      TCPIP$POP             Enabled
PORTMAPPER           111  TCP,UDP  TCPIP$PORTM             Enabled
REXEC                512  TCP      TCPIP$REXEC             Enabled
RLOGIN               513  TCP      not defined             Enabled
RSH                  514  TCP      TCPIP$RSH             Enabled
SMTP                  25  TCP      TCPIP$SMTP             Enabled
SNMP                 161  UDP      TCPIP$SNMP             Enabled
TELNET                23  TCP      not defined             Enabled
TFTP                  69  UDP      TCPIP$TFTP             Enabled
  1. This column lists those services with entries in the TCPIP services database. If not listed in this column, the service was never enabled during the configuration procedure (using TCPIP$CONFIG.COM). To enable additional services, run the TCPIP$CONFIG procedure.
  2. This column lists the port on which the service listens for connection requests. The port number is either the well-known port number for the service or an ephemeral port number assigned when the socket is assigned a protocol address.
  3. This column lists the TCP/IP protocol that the service uses to communicate with the client process.
  4. This column lists the process name for the service. If you use the DCL command SHOW SYSTEM /NETWORK, this is the process name you should see if the process is running.
  5. This column lists the IP address of the interface on which the service accepts connection requests. IP address indicates that the service will accept connection requests received on any of the local interfaces.
  6. This column lists whether the service is enabled or disabled. The term enabled indicates that the next time TCP/IP Services starts, TCP/IP Services starts all services that are marked in the service database as enabled. In this example, of the services listed, all services except finger will start the next time TCP/IP Services restarts.


    In this example, the finger service was configured with TCPIP$CONFIG. However, at some point, finger was disabled either by a TCPIP management command or by an incremental shutdown of the service.

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