Troubleshooting Q & A

New system disrupts LAN: I tried to attach a new system to our site LAN. To make the installation process faster, I copied over an /etc/rc.config.d/netconf file from another system on the site LAN and used it on the new system. When I booted up the system, the site LAN went down.

Answer: You probably didn't assign a new IP address and host name prior to rebooting the system. If any two systems on the LAN have the same IP address and host name, the LAN will go down. Check the IP address in the /etc/rc.config.d/netconf file against the IP address of your system and other systems on your network map to be sure that no duplicate IP addresses exist on the LAN.

Related Documentation: Refer to the ifconfig(1M) man page.

Determining interface name: How do I determine the name of the interface to be configured?

Answer: Use the lanscan command to determine the hardware path of the interface card that you want to configure. Then use the value displayed for the "Net-Interface Name PPA" field as the interface name.

Multiple LAN interfaces, intermittent failures: I have been having problems getting the two LAN interfaces on my system to operate at the same time. Occasionally the ethernet cards stop communicating with remote systems. When this happens, the remote system also cannot communicate with the local system.

Answer: Check that the two interfaces on your system do not have the same network number or, if you are subnetting, the same subnet address. If both LAN interfaces have the same value in the network (subnet) address portions of the IP address, the cards may not be enabled simultaneously (although they may both run separately.)

Related Documentation: Refer to chapter 6, "Network Addressing".

New system, can't reach some subnets: I recently tried to add a new system onto a subnet on our site LAN, and I am not able to communicate successfully with all LANs on the network.

Answer: Check the routing table to make sure the route for the LAN you are trying to communicate with has been properly configured. Execute netstat -rvn on both ends. Verify the subnet address, netmask and gateway.

Related Documentation: Refer to "Assigning Subnet Addresses" in chapter 6.

Configuring address 127.0.0.1: I tried to add the IP address, 127.0.0.1, and the system won't accept it.

Answer: Addresses with the format 127.n.n.n are reserved as loopback addresses. Select another IP address. You can obtain Class C addresses that are unique within the ARPANET by contacting Government Systems, Inc. Refer to "Assigning an Internet Address" in chapter 6 for more information.

Related Documentation: Refer to "Assigning an Internet Address" in chapter 6.

EISA configuration: I added my EISA card into my system prior to installing and configuring the software. When I looked at the instructions in chapter 1, I discovered that I should have added the hardware after the software. How can I recover from this situation?

Answer: Reboot the system twice after you have loaded the LAN software and then go directly to chapter 2 in this manual to configure the card.

Related Documentation: Refer to the eisa_config(1M) man page.

Displaying station address: How do I locate the station address of my LAN card?

Answer: Use the lanscan(1M) command to display the station addresses of all LAN cards in the system:

lanscan

Related Documentation: Refer to the lanscan(1M) man page.

Resetting LAN card: How do I reset the LAN card?

Answer: Run the lanadmin(1M) diagnostic by entering the following sequence of commands, where x is the Physical Point of Attachment (PPA) of the interface you want to reset. (Use the lanscan command to determine the PPA of the interface on the system.)

lanadmin
lan
ppa
x
reset
quit

Related Documentation: Refer to the lanadmin(1M) man page.

Tracing: What's the best way to obtain and format tracing information when I am using the nettl(1M) utility?

Answer: The HP field engineers recommend the following commands:

To begin LAN and loopback tracing, execute:

nettl -tn pduin pduout -e ns_ls_driver -f filename

To end LAN tracing, execute:

nettl -tf -e all

To format your entire LAN trace (no filtering), execute:

netfmt -Nnl -f filename.TRC1 > fmt1
netfmt -Nnl -f filename.TRC0 > fmt0

The file, filename.TRC0 is the most recent trace file. If this file does not contain the trace information you are looking for, check the filename.TRC1 file.

To format your LAN trace using a filter file, execute:

netfmt -c filterfile -N -f filename.TRC0 > fmt0

nettl(1M) appends TRC0 or TRC1 to the name you give the raw trace file.

Related Documentation: Refer to chapter 5, "LAN Resources."

Intermittent networking problems: I'm experiencing intermittent networking problems on my computer. What should I check to ensure proper operation of my networking software?

Answer: Upper layer software often requires loopback. Check /etc/rc.config.d/netconf to be sure that the loopback entry is correct. The line in netconf file should read:

LOOPBACK_ADDRESS=127.0.0.1

Related Documentation: Refer to chapter 6, "Network Addressing".

Performance: I've noticed a significant drop in system response time and performance. What steps can I take to improve it?

Answer: Performance may be affected by many different factors. Sometimes removing pseudo drivers from the kernel for networking software that you may not be using improves performance. The problems may also be in the upper layer software (ftp or telnet).

Also, it is possible that too little memory is allocated to hold fragmented messages in the IP layer. IP messages may be fragmented into smaller parts when the message is sent through the system. The fragments must be held in memory for some time so that the entire message can be reassembled because the fragments arrive at the destination at different times and possibly out of order. Normally, fragmentation reassembly memory is limited arbitrarily so that incomplete messages do not consume all of memory, which could cripple the system. During stressful networking activity, some fragments might never be delivered because they are typically dropped in transit, for example, due to a collision or resource limitations on an intermediate system. However, fragments might also not be delivered ("dropped") if there is insufficient fragmentation reassembly memory on the destination system during periods of high network activity. This can degrade performance due to retransmissions of data. If the problem is due to a high number of fragments dropped after time-out (see the output from the command netstat -sp ip), you might want to increase the size of the fragmentation reassembly memory by changing the ip_reass_mem_limit value using the ndd command. (The default is 2 MB for the system.) Enter the command /usr/bin/ndd -h to display ndd(1M) parameters and their use.

Deferred transmissions/collisions: Why is there a significant increase in the number of deferred transmissions and collisions on my network?

Answer: On IEEE802.3/Ethernet networks, a collision occurs when two or more stations try to transmit data simultaneously. A deferred transmission occurs if the network is busy when a station attempts to transmit data. The number of collisions and deferred transmissions on a node is directly related to the network load. As the network load increases, the number of collisions and deferred transmissions also increase.

When high-performance systems are placed on a LAN with lower-performance systems (HP or non-HP systems), it is possible for the high-performance systems to use a higher percentage of the LAN bandwidth with network traffic intensive applications. High-performance systems generate network traffic at a 10Mbits/s link rate, and lower-performance systems cannot match this rate. Heavily loaded LAN networks can result in lower throughput performance on lower-performance systems.

In general, the short term average load on an IEEE802.3/Ethernet LAN should not exceed more than 70% of the total bandwidth of the LAN. When it does exceed 70% of the total bandwidth, network performance begins to degrade due to an increase in collisions and deferred transmissions. When it consistently exceeds 70% of the total bandwidth, you may need to reconfigure the systems on your LAN. If you notice throughput/performance degradation on your system, contact your local HP Representative for additional assistance and consultation.

"No such interface": After I booted my Series 800 Model E, I found that networking failed. I found the following error in the /var/adm/rc.log file:

ifconfig lan0: no such interface

How do I resolve this problem?

Answer: This problem is caused by the LAN driver software disabling the LAN card because it was not connected to the LAN, or the LAN was down. Use lanadmin to reset the LAN card and run ifconfig to bring the card up.

"No such interface": When I configure an interface, ifconfig returns the error "no such interface." What should I do?

Answer: The numeric portion of the interface name is incorrect. Run the lanscan command to obtain a list of interface names.

"Plumbing error": When I configure an interface, ifconfig returns a "Plumbing error" message. What should I look for?

Answer: The interface name specified in the ifconfig run string is not defined in the /dev directory or is not a streams driver. The network device files /dev/ip and /dev/tcp are not defined.

Can't communicate outside local supernet: I recently tried to set up a supernet on my LAN. The systems in the supernet can communicate with one another, but they cannot communicate with systems outside the supernet.

Answer: Check the routing table on your system and the node you want to communicate with. If the system you want to communicate with does not support supernetting, you will have to configure a network route for each of the networks in the supernet. If the system you want to communicate with supports supernetting, you will only need to add a network route for the supernet.