[CentOS] Neighbour table overflow

John R Pierce pierce at hogranch.com
Fri Nov 28 22:13:59 UTC 2008

chloe K wrote:
> you have the network /20 so that you got this neigbour overlfow
> you should subnet it

no, no, NO.     his eth1 connection is from his ISP.  He /has/ to use 
the supplied netmask, he can't reconfigure their network segment.

now, why is ARP table is overflowing is another issue entirely.

Thomas, can you try this?   Do....

    arp -an | grep

and pick out the "MAC" address of your gateway router, this will look 
something like...

    ? ( at 00:17:CB:4F:97:81 [ether] on eth1

So, the MAC address above is 00:17:CB:4F:97:81 ... yours definitely will 
be different....   now,

    # tcpdump -i eth1 -n ip host 65.188.xxx.xxx and not ether host 

(replacing that with your gateway router's MAC address as determined 
from that ARP command, and xxx.xxx with your eth1 IP address as shown in 
`ifconfig eth1`)

this will catch all traffic between you and another IP on your ISP local 
segment thats NOT talking to the gateway router

paste 50 lines or so of the output of this here and maybe we can figure 
out whats going on.

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