We are experimenting with a RHEL 5 server, moving it back and forth between our DMZ and the Internet. The first time we moved it to the Internet and then back everything was fine. The second time we moved it back to the DMZ we are no longer able to communicate with anything outside of the DMZ (cannot ping, cannot ssh). We have completely shut off the firewall so that is not the issue. Here is our ifcfg-eth0 file:

DEVICE=eth0
BOOTPROTO=none
BROADCAST=10.10.10.255
HWADDR=00:06:5B:F3:ED:9E
IPADDR=10.10.10.251
NETMASK=255.255.255.0
NETWORK=10.10.10.0
GATEWAY=10.10.10.1
ONBOOT=yes
TYPE=Ethernet
USERCTL=no
IPV6INIT=no
PEERDNS=yes

This configuration worked fine until this morning. Does anybody have any idea what might be wrong?

Thanks,
Sanford Stein
CyberTools Inc.

There's nothing obviously wrong with the configuration. Does the output from ifconfig eth0 match the parameters from the configuration file? Does the gateway appear in the routing tables as shown by route -n?

If so, have you tried the usual troubleshooting tools? (ethtool eth0 or mii-tool eth0 to show the status of the network link, ping 10.10.10.1 followed by arp -n to verify layer 2 connectivity)

Ser,

Thanks for your quick response and for all the suggestions.

ifconfig-eth0 does show the proper parameters.

route -n does show gateway 10.10.10.1:

10.10.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0 eth0

Both ethtool and mii report the link as OK.

[root@olive ~]# ethtool eth0
Settings for eth0:
...
Link detected: yes
[root@olive ~]# mii-tool eth0
eth0: negotiated 100baseTx-FD flow-control, link ok

ping 10.10.10.1 works and arp -n shows the following:

10.10.10.1 ether 00:09:0F:11:49:49 C eth0

So, still looking...

Thanks,
SS

That rules out basic network settings and routing. How far does traceroute -n 8.8.8.8 get?

Your DmZ is using private IP addresses, so obviously there has to be a router/gateway/firewall doing NAT and port forwarding if this server is to be reachable from the outside. Have you checked those settings as well?

Ser,

traceroute -n 8.8.8.8 only gets to 10.10.10.1


Here are the settings on our router:
The WAN is
GATEWAY 75.150.108.254
range 75.150.108.249.253
NETMASK 255.255.255.248
BROADCAST 75.150.108.255
DNS 75.75.75.75 & 75.75.76.76

The IP on the DMZ is 10.10.10.251 and maps to 75.150.108.251

I know that all evidence point to a router issue, but we have checked these settings and believe them to be correct, and they were working prior to yesterday.

Thanks again,
Sanford Stein
CyberTools Inc.