Here are some of the more frequently asked questions about using Linux with an Ethernet connection. Some of the more specific questions are sorted on a `per manufacturer basis'. However, since this document is basically `old' by the time you get it, any `new' problems will not appear here instantly. For these, I suggest that you make efficient use of your newsreader. For example, nn users would type
nn -xX -s'3c'
to get all the news articles in your subscribed list that have `3c' in the subject. (ie. 3com, 3c509, 3c503, etc.) The moral: Read the man page for your newsreader.
I heard that there is an updated or alpha driver available for my card. Where can I get it?
The newest of the `new' drivers can be found on Donald's new
ftp site: cesdis.gsfc.nasa.gov in the
/pub/linux/ area. Things
change here quite frequently, so just look around for it.
Now, if it really is an alpha, or pre-alpha driver, then please treat it as such. In other words, don't complain because you can't figure out what to do with it. If you can't figure out how to install it, then you probably shouldn't be testing it. Also, if it brings your machine down, don't complain. Instead, send us a well documented bug report, or even better, a patch!
Note that some of the `useable' experimental/alpha drivers have
been included in the standard kernel source tree. When running
make config one of the first things you will be asked
is whether to ``Prompt for development and/or incomplete
code/drivers''. You will have to answer `Y' here to get
asked about including any alpha/experiemntal drivers.
People reading this while net-surfing may want to check out:
for the latest dirt on what is new and upcoming.
What needs to be done so that Linux can run two ethernet cards?
The hooks for multiple ethercards are all there. However, note that at the moment only one ethercard is auto-probed for by default. This helps to avoid possible boot time hangs caused by probing sensitive cards.
There are two ways that you can enable auto-probing for
the second (and third, and...) card. The easiest
method is to pass boot-time arguments to the kernel,
which is usually done by LILO. Probing for the
second card can be achieved by using a boot-time argument
as simple as ether=0,0,eth1. In this
case eth0 and eth1 will be assigned in the order
that the cards are found at boot. Say if you want
the card at 0x300 to be eth0 and
the card at 0x280 to be eth1 then you could use
LILO: linux ether=5,0x300,eth0 ether=15,0x280,eth1
The ether= command accepts more than the IRQ + i/o
+ name shown above. Please have a look at
Passing Ethernet Arguments...
for the full syntax, card specific parameters, and LILO tips.
These boot time arguments can be made permanent so that you
don't have to re-enter them every time. See the LILO
configuration option `append' in the LILO manual.
The second way (not recommended) is to edit the file
Space.c and replace the 0xffe0 entry for the
i/o address with a zero. The 0xffe0 entry tells it
not to probe for that device -- replacing it with a zero
will enable autoprobing for that device.
Note that if you are intending to use Linux as a gateway between two networks, you will have to re-compile a kernel with IP forwarding enabled. Usually using an old AT/286 with something like the `kbridge' software is a better solution.
If you are viewing this while net-surfing, you may wish to look at a mini-howto Donald has on his WWW site. Check out Multiple Ethercards.
For module users with 8390 based cards, you can have a single module control multiple cards of the same brand. Please see 8390 Based Cards as Modules for module specific information about using multiple cards.
Here is a list of some of the NE-2000 clones that are known to
have various problems. Most of them aren't fatal. In the case
of the ones listed as `bad clones' -- this usually indicates that
the cards don't have the two NE2000 identifier bytes. NEx000-clones
have a Station Address PROM (SAPROM) in the packet buffer memory space.
NE2000 clones have 0x57,0x57 in bytes 0x0e,0x0f
of the SAPROM, while other supposed NE2000 clones must be
detected by their SA prefix.
This is not a comprehensive list of all the NE2000 clones that
don't have the 0x57,0x57 in bytes 0x0e,0x0f
of the SAPROM. There are probably hundreds of them. If you
get a card that causes the driver to report an `invalid
signature' then you will have to add your cards signature
to the driver. The process for doing this is described
below.
Accton NE2000 -- might not get detected at boot, see below.
Aritsoft LANtastic AE-2 -- OK, but has flawed error-reporting registers.
AT-LAN-TEC NE2000 -- clone uses Winbond chip that traps SCSI drivers
ShineNet LCS-8634 -- clone uses Winbond chip that traps SCSI drivers
Cabletron E10**, E20**, E10**-x, E20**-x -- bad clones, but the driver checks for them. See E10**.
D-Link Ethernet II -- bad clones, but the driver checks for them. See DE-100 / DE-200.
DFI DFINET-300, DFINET-400 -- bad clones, but the driver checks for them. See DFI-300 / DFI-400
EtherNext UTP8, EtherNext UTP16 -- bad clones, but the driver checks for them.
Problem: NE*000 card hangs machine, sometimes with a `DMA conflict' message, sometimes completely silently.
Reason: There were some bugs in the driver and the upper networking layers that caused this. They have been fixed in kernels v1.2.9 and above. Upgrade your kernel.
Problem: NE*000 card hangs machine during NE probe, or can not read station address properly.
Reason: Kernels previous to v1.3.7 did not fully reset the card after finding it at boot. Some cheap cards are not left in a reasonable state after power-up and need to be fully reset before any attempt is made to use them. Also, a previous probe may have upset the NE card prior to the NE probe taking place. In that case, look in to using the ``reserve='' boot keyword to protect the card from other probes.
Problem: NE*000 driver reports `not found (no reset ack)' during boot probe.
Reason: This is related to the above change. After the initial verification that an 8390 is at the probed i/o address, the reset is performed. When the card has completed the reset, it is supposed to acknowedge that the reset has completed. Your card doesn't, and so the driver assumes that no NE card is present.
Solution:
You can tell the driver that you have a bad card by using
an otherwise unused mem_end hexidecimal value of 0xbad at
boot time. You have to also supply a non-zero i/o base
for the card when using the 0xbad override. For example,
a card that is at 0x340 that doesn't ack the reset
would use something like:
LILO: linux ether=0,0x340,0,0xbad,eth0
This will allow the card detection to continue, even if your card doesn't ACK the reset.
Problem: NE*000 card hangs machine at first network access.
Reason: This problem has been reported for kernels as old as 1.1.57 to the present. It appears confined to a few software configurable clone cards. It appears that they expect to be initialized in some special way.
Solution: Several people have reported that running the supplied DOS software config program and/or the supplied DOS driver prior to warm booting (i.e. loadlin or the `three-finger-salute') into linux allowed the card to work. This would indicate that these cards need to be initialized in a particular fashion, slightly different than what the present Linux driver does.
Problem:
NE*000 ethercard at 0x360 doesn't get detected anymore.
Reason:
Recent kernels ( > 1.1.7X) have more sanity checks with respect
to overlapping i/o regions. Your NE2000 card is 0x20 wide in
i/o space, which makes it hit the parallel port at 0x378.
Other devices that could be there are the second floppy
controller (if equipped) at 0x370 and the secondary
IDE controller at 0x376--0x377.
If the port(s) are already registered by another driver, the
kernel will not let the probe happen.
Solution:
Either move your card to an address like 0x280, 0x340, 0x320
or compile without parallel printer support.
Problem: Network `goes away' every time I print something (NE2000)
Reason: Same problem as above, but you have an older kernel that doesn't check for overlapping i/o regions. Use the same fix as above, and get a new kernel while you are at it.
Problem: NE*000 ethercard probe at 0xNNN: 00 00 C5 ... not found. (invalid signature yy zz)
Reason:
First off, do you have a NE1000 or NE2000 card at the addr. 0xNNN?
And if so, does the hardware address reported look like a valid
one? If so, then you have a poor NE*000 clone. All NE*000 clones
are supposed to have the value 0x57 in bytes 14 and 15 of the
SA PROM on the card. Yours doesn't -- it has `yy zz' instead.
Solution:
There are two ways to get around this. The easiest is to
use an 0xbad mem_end value as described above for the
`no reset ack' problem. This will bypass the signature check,
as long as a non-zero i/o base is also given. This way no
recompilation of the kernel is required.
The second method involves changing the driver itself, and then recompiling your kernel. The driver (/usr/src/linux/drivers/net/ne.c) has a "Hall of Shame" list at about line 42. This list is used to detect poor clones. For example, the DFI cards use `DFI' in the first 3 bytes of the prom, instead of using 0x57 in bytes 14 and 15, like they are supposed to.
You can determine what the first 3 bytes of your card PROM are by adding a line like:
printk("PROM prefix: %2.2x %2.2x %2.2x\n",SA_prom[0],SA_prom[1],SA_prom[2]);
into the driver, right after the error message you got above, and just before the "return ENXIO" at line 227.
Reboot with this change in place, and after the detection fails, you will get the three bytes from the PROM like the DFI example above. Then you can add your card to the bad_clone_list[] at about line 43. Say the above line printed out:
PROM prefix: 0x3F 0x2D 0x1C
after you rebooted. And say that the 8 bit version of your card was called the "FOO-1k" and the 16 bit version the "FOO-2k". Then you would add the following line to the bad_clone_list[]:
{"FOO-1k", "FOO-2k", {0x3F, 0x2D, 0x1C,}},
Note that the 2 name strings you add can be anything -- they are just printed at boot, and not matched against anything on the card. You can also take out the "printk()" that you added above, if you want. It shouldn't hit that line anymore anyway. Then recompile once more, and your card should be detected.
Problem:
Errors like DMA address mismatch
Is the chip a real NatSemi 8390? (DP8390, DP83901, DP83902 or DP83905)?
If not, some clone chips don't correctly implement the transfer
verification register. MS-DOS drivers never do error checking,
so it doesn't matter to them. (Note: The DMA address check is not done
by default as of v1.2.4 for performance reasons. Enable it with
the `NE_SANITY' define in ne.c if you want the check done.)
Are most of the messages off by a factor of 2? If so: Are you using the NE2000 in a 16 bit slot? Is it jumpered to use only 8 bit transfers?
The Linux driver expects a NE2000 to be in a 16 bit slot. A NE1000 can be in either size slot. This problem can also occur with some clones, notably older D-Link 16 bit cards, that don't have the correct ID bytes in the station address PROM.
Are you running the bus faster than 8Mhz? If you can change the speed (faster or slower), see if that makes a difference. Most NE2000 clones will run at 16MHz, but some may not. Changing speed can also mask a noisy bus.
What other devices are on the bus? If moving the devices around changes the reliability, then you have a bus noise problem -- just what that error message was designed to detect. Congratulations, you've probably found the source of other problems as well.
Problem: The machine hangs during boot right after the `8390...' or `WD....' message. Removing the NE2000 fixes the problem.
Solution:
Change your NE2000 base address to something like 0x340.
Alternatively, you
can use the ``reserve='' boot argument in conjunction with
the ``ether='' argument to protect the card from other
device driver probes.
Reason: Your NE2000 clone isn't a good enough clone. An active NE2000 is a bottomless pit that will trap any driver autoprobing in its space. Changing the NE2000 to a less-popular address will move it out of the way of other autoprobes, allowing your machine to boot.
Problem: The machine hangs during the SCSI probe at boot.
Reason: It's the same problem as above, change the ethercard's address, or use the reserve/ether boot arguments.
Problem: The machine hangs during the soundcard probe at boot.
Reason: No, that's really during the silent SCSI probe, and it's the same problem as above.
Problem: NE2000 not detected at boot - no boot messages at all
Solution: There is no `magic solution' as there can be a number of reasons why it wasn't detected. The following list should help you walk through the possible problems.
1) Build a new kernel with only the device drivers that you need.
Verify that you are indeed booting the fresh kernel. Forgetting to
run lilo, etc. can result in booting the old one. (Look closely at
the build time/date reported at boot.) Sounds obvious, but we have
all done it before. Make sure the driver is in fact included in
the new kernel, by checking the System.map file for names
like ne_probe.
2) Look at the boot messages carefully. Does it ever even mention
doing a ne2k probe such
as `NE*000 probe at 0xNNN: not found (blah blah)'
or does it just fail silently. There is a big difference.
Use dmesg|more
to review the boot messages after logging in, or hit Shift-PgUp
to scroll the screen up after the boot has completed and the login
prompt appears.
3) After booting, do a cat /proc/ioports and verify
that the full iospace that the card will require is vacant. If
you are at 0x300 then the ne2k driver will ask
for 0x300-0x31f. If any other device driver has registered
even one port anywhere in that range, the probe will not
take place at that address and will silently continue to the next
of the probed addresses. A common case is having the lp driver
reserve 0x378 which stops the ne driver from
probing 0x360.
4) Same as above for cat /proc/interrupts. Make sure no
other device has registered the interrupt that you set
the ethercard for. In this case, the probe will happen, and the
ether driver will complain loudly at boot about not being able to
get the desired IRQ line.
5) If you are still stumped by the silent failure of the driver, then edit it and add some printk() to the probe. For example, with the ne2k you could add/remove lines (marked with a `+' or `-') in net/ne.c like:
int reg0 = inb_p(ioaddr);
+ printk("NE2k probe - now checking %x\n",ioaddr);
- if (reg0 == 0xFF)
+ if (reg0 == 0xFF) {
+ printk("NE2k probe - got 0xFF (vacant i/o port)\n");
return ENODEV;
+ }
Then it will output messages for each port address that it checks, and you will see if your card's address is being probed or not.
6) You can also get the ne2k diagnostic from Don's ftp site (mentioned in the howto as well) and see if it is able to detect your card after you have booted into linux. Use the "-p 0xNNN" option to tell it where to look for the card. (The default is 0x300 and it doesn't go looking elsewhere, unlike the boot-time probe.) The output from when it finds a card will look something like:
Checking the ethercard at 0x300.
Register 0x0d (0x30d) is 00
Passed initial NE2000 probe, value 00.
8390 registers: 0a 00 00 00 63 00 00 00 01 00 30 01 00 00 00 00
SA PROM 0: 00 00 00 00 c0 c0 b0 b0 05 05 65 65 05 05 20 20
SA PROM 0x10: 00 00 07 07 0d 0d 01 01 14 14 02 02 57 57 57 57
NE2000 found at 0x300, using start page 0x40 and end page 0x80.
Your register values and PROM values will probably be different.
Note that all the PROM values are doubled for a 16 bit card, and
that the ethernet address (00:00:c0:b0:05:65) appears in the
first row, and the double 0x57 signature appears at the
end of the PROM.
The output from when there is no card installed at 0x300
will look something like this:
Checking the ethercard at 0x300. Register 0x0d (0x30d) is ff Failed initial NE2000 probe, value ff. 8390 registers: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff SA PROM 0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff SA PROM 0x10: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff Invalid signature found, wordlength 2.
The 0xff values arise because that is the value that
is returned when one reads a vacant i/o port. If you happen
to have some other hardware in the region that is probed, you
may see some non 0xff values as well.
7) Try warm booting into linux from a DOS boot floppy (via loadlin) after running the supplied DOS driver or config program. It may be doing some extra (i.e. non-standard) "magic" to initialize the card.
8) Try Russ Nelson's ne2000.com packet driver to see if even it can see your card -- if not, then things do not look good. Example:
A:> ne2000 0x60 10 0x300
The arguments are software interrupt vector, hardware IRQ, and i/o base. You can get it from any msdos archive in pktdrv11.zip -- The current version may be newer than 11.
Problem: You get messages such as the following:
eth0: bogus packet size: 65531, status=0xff, nxpg=0xff
Reason: There is a shared memory problem.
Solution:
The most common reason for this is PCI machines that are
not configured to map in ISA memory devices. Hence you
end up reading the PC's RAM (all 0xff values) instead of
the RAM on the card that contains the data from the
received packet.
Other typical problems that are easy to fix are board conflicts, having cache or `shadow ROM' enabled for that region, or running your ISA bus faster than 8Mhz. There are also a surprising number of memory failures on ethernet cards, so run a diagnostic program if you have one for your ethercard.
Problem: SMC EtherEZ doesn't work in non-shared memory (PIO) mode.
Reason: Older versions of the Ultra driver only supported the card in the shared memory mode of operation.
Solution: The driver in kernel version 2.0 and above also supports the programmed i/o mode of operation. Upgrade to v2.0, or get the drop-in replacement for kernel v1.2.13 from Donald's ftp/www site.
Problem: Old wd8003 and/or jumper-settable wd8013 always get the IRQ wrong.
Reason: The old wd8003 cards and jumper-settable wd8013 clones don't have the EEPROM that the driver can read the IRQ setting from. If the driver can't read the IRQ, then it tries to auto-IRQ to find out what it is. And if auto-IRQ returns zero, then the driver just assigns IRQ 5 for an 8 bit card or IRQ 10 for a 16 bit card.
Solution: Avoid the auto-IRQ code, and tell the kernel what the IRQ that you have jumpered the card to is via a boot time argument. For example, if you are using IRQ 9, using the following should work.
LILO: linux ether=9,0,eth0
Problem: SMC Ultra card is detected as wd8013, but the IRQ and shared memory base is wrong.
Reason: The Ultra card looks a lot like a wd8013, and if the Ultra driver is not present in the kernel, the wd driver may mistake the ultra as a wd8013. The ultra probe comes before the wd probe, so this usually shouldn't happen. The ultra stores the IRQ and mem base in the EEPROM differently than a wd8013, hence the bogus values reported.
Solution: Recompile with only the drivers you need in the kernel. If you have a mix of wd and ultra cards in one machine, and are using modules, then load the ultra module first.
Problem: The 3c503 picks IRQ N, but this is needed for some other device which needs IRQ N. (eg. CD ROM driver, modem, etc.) Can this be fixed without compiling this into the kernel?
Solution: The 3c503 driver probes for a free IRQ line in the order {5, 9/2, 3, 4}, and it should pick a line which isn't being used. Very old drivers used to pick the IRQ line at boot-time, and the current driver (0.99pl12 and newer) chooses when the card is open()/ifconfig'ed.
Alternately, you can fix the IRQ at boot by passing parameters via LILO. The following selects IRQ9, base location 0x300, <ignored value>, and if_port #1 (the external transceiver).
LILO: linux ether=9,0x300,0,1,eth0
The following selects IRQ3, probes for the base location, <ignored value>, and the default if_port #0 (the internal transceiver)
LILO: linux ether=3,0,0,0,eth0
Problem: 3c503: configured interrupt X invalid, will use autoIRQ.
Reason: The 3c503 card can only use one of IRQ{5, 2/9, 3, 4} (These are the only lines that are connected to the card.) If you pass in an IRQ value that is not in the above set, you will get the above message. Usually, specifying an interrupt value for the 3c503 is not necessary. The 3c503 will autoIRQ when it gets ifconfig'ed, and pick one of IRQ{5, 2/9, 3, 4}.
Solution: Use one of the valid IRQs listed above, or enable autoIRQ by not specifying the IRQ line at all.
Problem: The supplied 3c503 drivers don't use the AUI (thicknet) port. How does one choose it over the default thinnet port?
Solution: The 3c503 AUI port can be selected at boot-time with 0.99pl12 and later. The selection is overloaded onto the low bit of the currently-unused dev->rmem_start variable, so a boot-time parameter of:
LILO: linux ether=0,0,0,1,eth0
should work. A boot line to force IRQ 5, port base 0x300, and use an external transceiver is:
LILO: linux ether=5,0x300,0,1,eth0
With kernels 1.3.42 and newer, you can specify the
AUI port when loading as a module as well. Just append
xcvr=1 to the insmod command line along with
your i/o and irq values.
The usual reason for this is that people are using a kernel that does not have support for their particular card built in. If you are using a pre-compiled kernel that is part of a distribution set, then check the documentation to see which kernel you installed, and if it was built with support for your particular card. If it wasn't, then your options are to try and get one that has support for your card, or build your own.
It is usually wise to build your own kernel with only the drivers you need, as this cuts down on the kernel size (saving your precious RAM for applications!) and reduces the number of device probes that can upset sensitive hardware. Building a kernel is not as complicated as it sounds. You just have to answer yes or no to a bunch of questions about what drivers you want, and it does the rest.
The next main cause is having another device using part
of the i/o space that your card needs. Most cards are
16 or 32 bytes wide in i/o space. If your card is set
at 0x300 and 32 bytes wide, then the driver will ask
for 0x300-0x31f. If any other device driver has registered
even one port anywhere in that range, the probe will not
take place at that address and the driver will silently
continue to the next of the probed addresses. So, after
booting, do a cat /proc/ioports and verify that the
full iospace that the card will require is vacant.
Another problem is having your card jumpered to an i/o
address that isn't probed by default. There is a list
probed addresses for each card
in this document. Even if the i/o setting of your card is
not in the list of porbed addresses, you can supply
it at boot with the ether= command as described in
Passing Ethernet Arguments...
ifconfig reports the wrong i/o address for the card.No it doesn't. You are just interpreting it incorrectly.
This is not a bug, and the numbers reported are correct. It just
happens that some 8390 based cards (wd80x3, smc-ultra, etc) have the
actual 8390 chip living at an offset from the first assigned i/o port.
Try cd /usr/src/linux/drivers/net;grep NIC_OFFSET *.c|more
to see what is going on. This is the value stored in
dev->base_addr, and is what ifconfig reports. If you
want to see the full range of ports that your card uses, then try
cat /proc/ioports which will give the numbers you expect.
This will usually show up as reads of lots of 0xffff values.
No shared memory cards of any type will work in a PCI machine
unless you have the PCI ROM BIOS/CMOS SETUP configuration set
properly. You have to set it to allow shared memory access
from the ISA bus for the memory region that your card is trying
to use. If you can't figure out which settings are applicable
then ask your supplier or local computer guru. For AMI BIOS,
there is usually a "Plug and Play" section where there will
be an ``ISA Shared Memory Size'' and ``ISA Shared Memory Base''
settings. For cards like the wd8013 and SMC Ultra, change the
size from the default of `Disabled' to 16kB, and change the base
to the shared memory address of your card.
A quirk of the NexGen CPU caused all users with 8390 based cards (wd80x3, 3c503, SMC Ultra/EtherEZ, ne2000, etc.) to get these error messages. Kernel versions 2.0 and above do not have these problems. Upgrade your kernel.
Werner Almesberger has been playing around with ATM support for linux. He has been working with the Efficient Networks ENI155p board ( Efficient Networks) and the Zeitnet ZN1221 board ( Zeitnet).
Werner says that the driver for the ENI155p is rather stable, while the driver for the ZN1221 is presently unfinished.
Check the latest/updated status at the following URL:
Is there FDDI support for Linux?
Donald writes: `No, there is no Linux driver for any FDDI boards. I come from a place with supercomputers, so an external observer might think FDDI would be high on my list. But FDDI never delivered end-to-end throughput that would justify its cost, and it seems to be a nearly abandoned technology now that 100base{X,Anynet} seems imminent. (And yes, I know you can now get FDDI boards for <$1K. That seems to be a last-ditch effort to get some return on the development investment. Where is the next generation of FDDI going to come from?)'
However, Larry Stefani (stefani@lkg.dec.com) recently announced a beta driver for v2.0 with DEC's DEFEA and DEFPA cards. You will have to contact him for more details.
Will Full Duplex give me 20MBps? Does Linux support it?
Full Duplex is at the wiring level of things, and has nothing to do with the drivers in linux.
Cameron Spitzer writes the following about full duplex 10Base-T cards: ``If you connect it to a full duplex switched hub, and your system is fast enough and not doing much else, it can keep the link busy in both directions. There is no such thing as full duplex 10BASE-2 or 10BASE-5 (thin and thick coax). Full Duplex works by disabling collision detection in the adapter. That's why you can't do it with coax; the LAN won't run that way. 10BASE-T (RJ45 interface) uses separate wires for send and receive, so it's possible to run both ways at the same time. The switching hub takes care of the collision problem. The signalling rate is 10 Mbps.''
As of v2.0, only the 3c509, depca, de4x5 and all the 8390 drivers (wd, smc-ultra, ne, 3c503, etc.) have been made `architecture independent' so as to work on the DEC Alpha CPU based systems.
Note that the changes that are required aren't that complicated. You only need to do the following:
-multiply all jiffies related values by HZ/100 to account
for the different HZ value that the Alpha uses.
(i.e timeout=2; becomes timeout=2*HZ/100;)
-replace any i/o memory (640k to 1MB) pointer dereferences with the appropriate readb() writeb() readl() writel() calls, as shown in this example.
- int *mem_base = (int *)dev->mem_start; - mem_base[0] = 0xba5eba5e; + unsigned long mem_base = dev->mem_start; + writel(0xba5eba5e, mem_base);
-replace all memcpy() calls that have i/o memory as source or
target destinations with the appropriate one of
memcpy_fromio() or memcpy_toio().
Can I link 10BaseT (RJ45) based systems together without a hub?
You can link 2 machines easily, but no more than that, without extra devices/gizmos. See Twisted Pair -- it explains how to do it. And no, you can't hack together a hub just by crossing a few wires and stuff. It's pretty much impossible to do the collision signal right without duplicating a hub.
I get a bunch of `SIOCSIFxxx: No such device' messages at boot, followed by a `SIOCADDRT: Network is unreachable' What is wrong?
Your ethernet device was not detected at boot, and when
ifconfig and route are run, they have no device
to work with. Use dmesg | more to review the
boot messages and see if there are any messages about
detecting an ethernet card.
I get `SIOCSFFLAGS: Try again' when I run `ifconfig' -- Huh?
Some other device has taken the IRQ that your ethercard
is trying to use, and so the ethercard can't use the IRQ.
You don't necessairly need to reboot to resolve this, as
some devices only grab the IRQs when they need them and
then release them when they are done. Examples are some
sound cards, serial ports, floppy disk driver, etc. You
can type cat /proc/interrupts to see which interrupts
are presently in use. Most of the
Linux ethercard drivers only grab the IRQ when they are
opened for use via `ifconfig'. If you can get the other
device to `let go' of the required IRQ line, then you
should be able to `Try again' with ifconfig.
When I run ifconfig with no arguments, it reports that LINK is UNSPEC (instead of 10Mbs Ethernet) and it also says that my hardware address is all zeros.
This is because people are running a newer version of the `ifconfig' program than their kernel version. This new version of ifconfig is not able to report these properties when used in conjunction with an older kernel. You can either upgrade your kernel, `downgrade' ifconfig, or simply ignore it. The kernel knows your hardware address, so it really doesn't matter if ifconfig can't read it.
When I run ifconfig with no arguments, it reports that I have a huge error count in both rec'd and transmitted packets. It all seems to work ok -- What is wrong?
Look again. It says RX packets big number PAUSE
errors 0 PAUSE dropped 0 PAUSE overrun 0.
And the same for the TX column.
Hence the big numbers you are seeing are the total number of
packets that your machine has rec'd and transmitted.
If you still find it confusing, try typing
cat /proc/net/dev instead.
/dev/ for EthercardsI have /dev/eth0 as a link to /dev/xxx. Is this right?
Contrary to what you have heard, the files in /dev/* are not used.
You can delete any /dev/wd0, /dev/ne0 and similar entries.
Should I disable trailers when I `ifconfig' my ethercard?
You can't disable trailers, and you shouldn't want to. `Trailers' are a hack to avoid data copying in the networking layers. The idea was to use a trivial fixed-size header of size `H', put the variable-size header info at the end of the packet, and allocate all packets `H' bytes before the start of a page. While it was a good idea, it turned out to not work well in practice. If someone suggests the use of `-trailers', note that it is the equivalent of sacrificial goats blood. It won't do anything to solve the problem, but if problem fixes itself then someone can claim deep magical knowledge.
How do I get access to the raw ethernet device in linux, without going through TCP/IP and friends?
int s=socket(AF_INET,SOCK_PACKET,htons(ETH_P_ALL));
This gives you a socket receiving every protocol type.
Do recvfrom() calls to it and it will fill the sockaddr
with device type in sa_family and the device name in the
sa_data array. I don't know who originally invented
SOCK_PACKET for Linux (its been in for ages) but its superb stuff.
You can use it to send stuff raw too via sendto() calls.
You have to have root access to do either of course.