[CentOS] Neighbour table overflow

Thomas Dukes tdukes at sc.rr.com
Fri Nov 28 19:36:20 UTC 2008


 

-----Original Message-----
From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On Behalf
Of Robert Moskowitz
Sent: Friday, November 28, 2008 12:20 PM
To: CentOS mailing list
Subject: Re: [CentOS] Neighbour table overflow

tdukes at sc.rr.com wrote:
> ---- Robert Moskowitz <rgm at htt-consult.com> wrote: 
>   
>> Thomas Dukes wrote:
>>     
>>>  
>>>
>>> *From:* centos-bounces at centos.org [mailto:centos-bounces at centos.org]
>>> *On Behalf Of *chloe K
>>> *Sent:* Thursday, November 27, 2008 9:10 PM
>>> *To:* CentOS mailing list
>>> *Subject:* Re: [CentOS] Neighbour table overflow
>>>
>>> what is your netmask?  
>>>  
>>> eth0 = 255.255.240.0
>>>       
>> Why do you have such a large subnet?  There are a number of potential 
>> performance problems with such a setup.  I typically only see this in 
>> large, bridged wireless campuses.  Little justification for it in a 
>> wired network.  (I do have lots of networking experience and 
>> knowledge, having consulted with a number of large deployments).
>>
>> Even with a large subnet, you should not be arping everywhere.  
>> Either two things are happening:
>>
>> Your system is recording every ARP request it sees ('Who has IP
>> x.x.x.x') to avoid arping later.  Bad behaviour (IMNSHO), given your 
>> network.
>>
>> Your system is ARPing for every IP address in the subnet to learn all 
>> of its neighbors.  WHy would it do that?  Unless you have some 
>> snooping software running on your system.
>>
>>     
> Hi Robert,
>
> I did not set this value.  Something did but not me.
>
> I am on a roadrunner connection with a dynamic ip.  What do you suggest I
change it to?
You might not have much control over it if you are using DHCP.

route -n


Here's the output from route -n:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use
Iface
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 eth1
65.188.0.0      0.0.0.0         255.255.240.0   U     0      0        0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U     0      0        0 eth1
0.0.0.0         65.188.0.1      0.0.0.0         UG    0      0        0 eth0


will supply you with your router address. Once you now that and your
assigned IP address (and lease) you can use ifconfig to change your netmask
so that your router and you are in the same subnet.

What is the address also of your nameserver (/etc/resolv.conf) and mail
server? If these are also within that hugh subnet, your netmask has to keep
them 'local'.

My nameservers are:  24.25.5.149 and 24.25.5.150

Mailservers:  75.180.132.77 and 75.180.132.33

Roadrunner.... hmm.


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