I have an Centos 5.2 server running sendmail spamassasin squid and apache.
everything was working fine until a couple of weeks a go.
Suddently I realise that I can't access by website and as well I can not send any e-mails. I tried to shh to the machine to rectify the problem. But I didn't have any access .
I get console access and I see all my interfaces up sendmail is running as well apache and all other services.
Of course I didn't find any errors in any of my logs.
So I thought it has to do with my gateway. I try to ping it, but no response. I did reset my rooter but still the same.
I restarted all services plus the networking. Again the same it seemed like my gateway was unreachable.
OK here comes the WEIRD part. As soon as I restart my server I can ping my gateway and all problems have been rectified.


So I think it's routing problem but I can't figure out what exactly or why this is happening.
Thank you in advance for any help.

hi,

it seems that you were having some layer 2 problem,
perhaps just bad NIC, bad RJ connector/wiring or something like that?
just check your ifconfig output - observe those TX/RX error,
and check your NIC or switch led light.

HTH.

Could be anything, if it doesn't reoccur I'd probably be tempted to ignore it for the time being, it could have been a hiccup or a bad command that was passed like "ifconfig eth0 xx.xx.xx.xx netmask 255.0.0.0" when netmask should be 255.255.255.0. If it reoccurs I'd look into the network card first as well as getting the physical server checked if possible (that is see that network connection and activity lights are active).

I have checked all ready RX/TX errors but I didn't found anything everything was fine in all my nics.
As well I don't think it's wiring problem because my interfaces follow different routes. And when I lose connectivity, I lose connectivity through all interfaces.
My eth0 is a point to point line that goes to the router and then to the outside world
My eth1 is an interface that links me with another node for redundancy reasons in case I lose first node and the two nodes are connected together through a small switch.
My eth2 Interface connects me through a router with an dsl line.
So I don't think it's a wiring or hardware malfunction problem.

It has occurred more than five times in a period of two weeks which is unacceptable.
I am the only administrator for this system and I haven't touched anything in the system concerning the network(ifconfig, route add route delete ....)
Third I am losing connectivity to all three interfaces so it's a bit rare to have a hardware problem in all three of them.
Worst of all, one of the cards I am losing connectivity is my ssh admin interface so I can't even restart the server. I have to go there in person to get console access(it's being twice that this thing happened over the weekend).

hi,

try to ping somewhere at the console first, and
please check your ip_forward,

no offense - this small switch could also gives you the problem if you have to many broadcast inside it, and sometimes it acts - sorry - "silly". if you are having this kind of problem one more time - dont reboot the server - try to power cycle that small switch and lets see how it goes.

HTH.