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tlug: neighbor table overflow

Okay, here's one for people who know something about how the kernel
handles memory and stuff. 

I have an old 486DX/2 box (a Compaq Prolinea) that a colleague left in the
computer room to die.  I have installed Linux in it, and set it up as a
ringback server. 

To save on IP addresses in our faculty, the ringback PPP connection uses
IP addresses in a local range, and the ringback server masquerades its own
address on packets from the home machine that are put on the Internet. 

That all seems to work fine.  After putting in this much work, though, I
thought I might as well make this machine a masquerading firewall for my
office, so I would use just one (1) public IP address for all of my
machines, including the dusty ones.

I had an Allied Telesis card in one slot, which turned out to respond to
the at1700 driver with io=0x300 and irq=15.  I have two other cards lying
around.  One is a more recent edition of the AT card, which uses the same
base address and IRQ; so that one is out.  The other is an old short-slot
Western Digital ISA card that uses base address io=0x290 and irq=5. 

I have used the AT card on the network.  It seems OK.  When I slotted in
the WD card, and set it up on a private interface to my laptop, I couldn't
ping the laptop's address on the same private network.  Worse, I can't
ping the address of the private interface card itself.  Any attempt to
generate network traffic on the card generates a leisurely stream of
messages that read:

  * neighbor table overflow *

It will not surprise anyone to learn that I have ab-solutely no idea what
that means.  A conflict between the two cards (0x290 and 0x300 maybe are
kinda close together ... ?); an attempt to use a Stone Age WDC network
adapter with a modern-age all-singing all-dancing Linux kernel; a
pre-fried card; and Good Old Fashioned Bad Luck all come to mind.

Other things that might have an effect on this are:

  o The machine whinges about bad memory at startup (but seems to
    adjust okay --- I successfully compiled a kernel on it, and
    it doesn't collapse when it runs into swap).

  o I'm using ipchains to perform the masquerading magic
    (but this misbehavior occurs even when the firewall
    is not up yet).

Can anyone out there put a gloss on this?

Frank G Bennett, Jr         @@
Faculty of Law, Nagoya Univ () email:
Tel: +81[(0)52]789-2239     ()

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