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@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"
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@pgtm ~]# cat /etc/resolv.conf # Generated by NetworkManager search gtm.gob.cu nameserver 192.168.41.17
[root@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@nauta.cu
First guess is that you may have two devices on the network with the same ip address.
Next time this happens, try doing
1. 'arp -n' from a machine other than the db server 2. ping the other machine from the db server, then 3. 'arp -n' from the other machine
Compare the outputs of the two invocations of arp. If the outputs show different MAC addresses for 192.168.41.4 then you have two different devices with the same IP address.