[CentOS] Network conections problems

[Istimsak Abdulbasir]

On Feb 20, 2017 2:42 PM, "Rommel Rodriguez Toirac" <rommelrt at nauta.cu>
wrote:

Hi;
 I have a CentOS 6.8 x86_64 server where just run Oracle 11g 64 bit data
base server. Is happen that sometimes it loose all connections (no ping, I
can not access via ssh, no TNSping of Oracle server have success). When
this happend I make ping from this server to some IP address of my network
and then everything work fine again. I check logs looking for some mistake
or problem in the network device, but I do not find anything or maybe I not
looking where must be.
 I check that from a workstation (Windows XP or Windows 7 or Windows 10)
when I make ping to the server, after ~ 8 seconds in get answer and always
the first one is loose. If you try again ping, everything work fine (no
answers are loose)

C:\Users\administrator>ping pgtm.gtm.gob.cu

Haciendo ping a pgtm.gtm.gob.cu [192.168.41.4] con 32 bytes de datos:
Tiempo de espera agotado para esta solicitud.
Respuesta desde 192.168.41.4: bytes=32 tiempo<1m TTL=64
Respuesta desde 192.168.41.4: bytes=32 tiempo<1m TTL=64
Respuesta desde 192.168.41.4: bytes=32 tiempo<1m TTL=64

Estadísticas de ping para 192.168.41.4:
    Paquetes: enviados = 4, recibidos = 3, perdidos = 1
    (25% perdidos),
Tiempos aproximados de ida y vuelta en milisegundos:
    Mínimo = 0ms, Máximo = 0ms, Media = 0ms

This are some of the configs related with networks

[root at pgtm ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
TYPE=Ethernet
UUID=11dcddd4-6530-457a-8d3e-01a8339fb113
ONBOOT=yes
NM_CONTROLLED=yes
BOOTPROTO=none
HWADDR=6C:92:BF:26:C7:02
IPADDR=192.168.41.4
PREFIX=24
GATEWAY=192.168.41.1
DNS1=192.168.41.17
DOMAIN=gtm.gob.cu
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth0"
L

I noticed from your ipcfg-eth0 file, the address 192.168.41.1 is assigned
to eth0. When you typed the command "ifconfig", that same address was
assigned to eth1. Try changing the name of this file to ipcfg-eth1 and
restart networkmanager.

As was stated earlier, check your gateway and see what other devices could
be using that address. Put a block on that unknown MAC address if you can.

cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4
localhost4.localdomain4
::1         localhost localhost.localdomain localhost6
localhost6.localdomain6
192.168.41.4 pgtm pgtm.gtm.gob.cu

[root at pgtm ~]# cat /etc/resolv.conf
# Generated by NetworkManager
search gtm.gob.cu
nameserver 192.168.41.17

[root at pgtm mail]# cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=pgtm.gtm.gob.cu
GATEWAY=192.168.41.1

 Someone that happend something like this, or some place for where keep
looking to try to fix this loose of conection?
 Thank and sorry for my horryble English.

Rommel Rodriguez Toirac
rommelrt at nauta.cu
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