Technical data

Troubleshooting Techniques and Tools
1.2 Isolating Problems
37 mbufs allocated to OpenVMS VCI context block
1 mbufs allocated to OpenVMS ACP IPCACHE Structure
57 mbufs allocated to OpenVMS PROXY correlation records
66 mbufs allocated to OpenVMS PROXY host records
14 mbufs allocated to OpenVMS PROXY local user records
17 mbufs allocated to OpenVMS PROXY remote user records
17 mbufs allocated to OpenVMS Unix emulation stack (NFS, et al)
! This line indicates there are 24 sockets in use (1 mbuf allocated for each
socket).
" There are two protocol control blocks allocated for each TCP socket and one
protocol control block for each UDP socket. The 35 mbuf listed is a mix of
PCBs allocated for TCP and UDP sockets. Output from the TCPIP SHOW
DEVICE_SOCKET command will tell you how many TCP and UDP sockets
are allocated.
By comparing the information output from the netstat -m and the TCPIP
command SHOW DEVICE_SOCKET, you can estimate whether the system is
using an excessive amount of memory for the number of allocated sockets.
If you sense that TCP/IP Services is using an excessive amount of memory for the
number of sockets, there may be a memory leak. Capture the output from the
netstat -m and the TCPIP SHOW DEVICE_SOCKET commands and save for
documenting the condition.
Table 1–2 shows variations of the netstat command that can reveal network
problems.
Table 1–2
netstat Commands
Command Purpose
netstat -p ip Checks for bad checksums, length problems, excessive
redirects, and packets lost because of resource problems.
netstat -p tcp Checks for retransmissions, out of order packets, and bad
checksums.
netstat -p udp Looks for bad checksums and full sockets.
netstat -rs Obtains routing statistics.
netstat -s Simultaneously displays statistics related to the IP, ICMP,
TCP, and UDP protocol layers.
netstat -is Checks for network device driver errors.
For more information about netstat , see Appendix A.
1.2.5 Monitoring Network Traffic
You can use either of the following to monitor network traffic:
• The TCPTRACE command, described in Section 1.2.5.1
• The tcpdump utility, described in Section 1.2.5.2
1–8 Troubleshooting Techniques and Tools