Instructions to solve network problems

Support knowledgebase (cep_net_troubleshooting)

SuSE Linux: Versions up to (including) 7.3
Kernel: Versions since 2.0.

Request:

Procedure:

Check first, if the network device, the network card is recognized by the kernel. Correct function can be proven by looking into /var/log/messages which can be scanned to the keywords

• eth0 for Ethernet netzwerk cards,
• sdla for Frame relay devices
• atp for parallel port adapter
• arc für arcnet devices
• plip for parallel port devices
• slip_proto for Slip interfaces to boot
• mkiss_proto for KISS (AX25)
• strip_proto for Starmode Radio IP
• ppp_prot for PPP protocoll
• dummy for das dummy device
• eql for Line Balancing
• tr for Token Ring
• fddi for FDDI
• tunl for Tunnel device
• bif
• lo for loopback device
• isdn for ISDN device (Raw IP)
• ippp for ISDN device (IP over PPP on ISDN)
• ppp for PPP

If the support of the device is realized as module, the file /etc/conf.modules must be checked, whether the parameters included herein, especially ports, interrupts, memory, interface conform with the real world.

A typical entry looks like

# Aliases - specify your hardware

alias eth0 tulip

options tulip      options=0

Additionally, the loading operations of modules must be checked using command lsmod.

If a module or a kernel built in device has been found according to /var/log/messages, the configuration can be checked by the command ifconfig

A typical result screen looks like

eth0      Link encap:10Mbps Ethernet  HWaddr 00:40:05:41:4C:51
          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:22369990 errors:0 dropped:0 overruns:0
          TX packets:13964874 errors:2514 dropped:0 overruns:0
          Interrupt:9 Base address:0x6100

If the module cannot be loaded, or the kernel bound in driver cannot access the device, checks should be done:

1. Is it a ISA-PnP card? Then the recipe in "ISA-PnP: Configuring an ISA-PnP card" (http://sdb.suse.de/en/sdb/html/rb_isapnp.html) should be applied.
2. Is the appropriate driver in use? (e.g. the modern ne-driver is not suitable for PCI-ne-cards.
3. Is a more recent driver available for the device? It should be used. If necessary, it should be downloaded, see hints at the end of the article.
4. Is the card, the interface physically present?
5. Is the card, the interface configured correctly concerning interrupt, i/o-port, shared memory and DMA channel? If necessary, Linux or DOS programs must be used for configuration.
6. Do hardware conflicts exist?
• With ISA cards, interrupt, i/o port, shared memory and DMA channel must be proven. In case of ISA cards with shared memory areas, the BIOS must free that area, if necessary the range must be passed to the kernel, interrupt, DMA and i/o conflicts have to be removed by reconfiguring the involved cards.
• With PCI cards mainly interrupt conflicts occur. In the case of interrupt conflicts, checks have to be done on
1. the driver permits interrupt sharing
2. permutating the PCI cards into other PCI slots the interrupt assignment can be changed.
3. the BIOS assignment can be changed
7. On network interface cards with multiple media interaces (10MB/s 10Base2, 10BaseTP and AUI) or several transceiving standards (10MB/s, 100MB/s) the choice of the correct medium is to be checked. For PCMCIA network cards there is a special Linux program, which allows hot switching.
8. Faults in the transfer media have to be excluded. With more than two computers in the net, mutually connections should be built, the correct fitting and completeness of cabling must be proved, cable and auxiliary devices must be function proved.

If necessary the exchange of the card in doubt by a equal one and thereafter by a sample of completely different construction can be of great value to isolate the fault.

If the driver is loaded correctly, the interface eth0 can be configured by

ifconfig eth0 192.168.110.1 broadcast 192.168.110.255 netmask 255.255.255.0 up

route add -net 192.168.110.0 netmask 255.255.255.0 eth0

ping 192.168.110.1

If the commands ifconfig or route add fail, conflicts in IP addresses, routes and interface names might have been occured. The described configurations by hand should only be done for testing purposes, if the canonical configuration with YaST does not succeed. The final configuration will be done naturally with YaST.

The most recent network card drivers are available from http://www.scyld.com/network/. Those drivers replace their predecessors in their suitable directory and the kernel must be recompiled and reinstalled, see manual!

Purpose and practical instruction to use IP addresses

ISA-PnP: Configuring an ISA-PnP card