[CentOS] Neighbour table overflow

Thomas Dukes tdukes at sc.rr.com
Sat Nov 29 00:20:03 UTC 2008


-----Original Message-----
From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On Behalf
Of John R Pierce
Sent: Friday, November 28, 2008 5:14 PM
To: CentOS mailing list
Subject: Re: [CentOS] Neighbour table overflow

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

Hi John,

The output from arp -an | grep is:

? ( at 00:1B:54:CB:7A::05

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.

OK, I think you lost me on that last part.  I ran tcpdump -i eth1 -n ip host and got:

Tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes

0 packets captred
0 packets received by filter
0 packets dropped by kernel


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