Network inactivity ==> host disappears

Network inactivity ==> host disappears

Post by tah.. » Tue, 17 Aug 1999 04:00:00



Hi,

I've been wrestling with a strange networking
problem.  Here's what happens:

Accessing anything from my machine (R.H. 6.0, 3com
Etherlink XL PCI), works without a hitch.
However, if my machine is not engaged in any
network activity for around 30 minutes, then it
becomes inaccessible from anywhere else.  The
instant I ping some other machine from my machine,
my machine becomes accessible again.  But if I
don't do anything network related for around 30
minutes, my machine becomes inaccessible again.

It has nothing to do with power management, and
I've made sure that my ethernet module is not
being unloaded.  Also, ifconfig shows the
interface up and active.

I've scoured the net, and have found a few people
with similar symptoms, but I've never seen a
solution posted.

Thanks,
Taher

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Network inactivity ==> host disappears

Post by LT » Wed, 18 Aug 1999 04:00:00


Hi
I have been encountering a similar phenomenon (2.0.31 & 3Com etherlinx):

Try pinging around a bit on your network, then have a look at the Linux arp
table, you might find a load of entries with the C (Complete entry) flag,
but not the M (perManent entry). So you could try copying the entries
manually, as permanents... My guess is that the automatically generated
(somehow generated by pinging) arps get forgotten by the cache pretty soon.

Thats just a guess though,  I am pretty new to the game!
Tris

Quote:> However, if my machine is not engaged in any
> network activity for around 30 minutes, then it
> becomes inaccessible from anywhere else.  The
> instant I ping some other machine from my machine,
> my machine becomes accessible again.  But if I
> don't do anything network related for around 30
> minutes, my machine becomes inaccessible again.


 
 
 

Network inactivity ==> host disappears

Post by tah.. » Thu, 19 Aug 1999 04:00:00


I also suspect its arp, but it's not *my* arp table that can cause a
problem, it's the gateway's arp table.  I suspect that for some reason,
either the gateway is not sending the arp request properly, or I'm not
responding to it properly.  I guess some packet sniffing is in order.

Of course I could just have crond ping somebody every 10 minutes, but
I'd like to know what's really going on...

Taher



Quote:> Hi
> I have been encountering a similar phenomenon (2.0.31 & 3Com
> etherlinx):

> Try pinging around a bit on your network, then have a look at the
> Linux arp table, you might find a load of entries with the C
> (Complete entry) flag,
> but not the M (perManent entry). So you could try copying the entries
> manually, as permanents... My guess is that the automatically
> generated
> (somehow generated by pinging) arps get forgotten by the cache pretty
> soon.

> Thats just a guess though,  I am pretty new to the game!
> Tris

> > However, if my machine is not engaged in any
> > network activity for around 30 minutes, then it
> > becomes inaccessible from anywhere else.  The
> > instant I ping some other machine from my machine,
> > my machine becomes accessible again.  But if I
> > don't do anything network related for around 30
> > minutes, my machine becomes inaccessible again.

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1. telnet: only from host A -> B, but not host B-> A?

Hi, all,

I am currently using Solaris 2.5.1 and I have a weired problem:
I can telnet from host A to B without any problem, but I can not
telnet from host B to A. Host B has multiple NICs.

I feel strange if host B has no route to A, why I can telnet from
host A to B? How are the returning packets sent back to host A?

The following is the info of host A and B:

Thanks a lot.

SZ

IP of host A: 143.209.163.149

IPs of host B:
 201.45.100.100  host_B loghost
 201.45.101.100  host_B.pnet1
 #201.44.2.147   host_B.pnet2
 192.160.7.35    host_B.pnet2  <----this is one i can telnet from host A.

The routing table of host B is:

Routing Table:
   Destination           Gateway           Flags  Ref   Use   Interface
 -------------------- -------------------- ----- ----- ------ ---------
 201.45.100.0         host_B               U        3    336  pnet0
 201.45.101.0         host_B.pnet1         U        2    274  pnet1
 192.160.7.0          host_B.pnet2         U        2     97  pnet2
 224.0.0.0            host_B               U        3      0  pnet0
 default              192.160.7.33          UG       0    152
 localhost            localhost             UH       0  28126  lo0

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