Hello,

I have a Redhat server with IP range from 202.85.1.120-141 (i.e. interface in eth0, eth0:0, eth0:1, etc.), with netmask 255.255.255.0 and default gateway 202.85.1.1.

Now I am getting a strange problem that when I put the server online, all ip addresses of the server is reachable within same netmask (i.e. 202.85.1.xxx, I try to ping 202.85.1.120-141 and success). However, outside the subnet , they can only access 202.85.1.120 (eth0), and all ip aliases (i.e. 202.85.1.121-141) are not reachable at all.

Now I would like to ask:
1. What's wrong for this strange situation?
2. Which commands can I try for validation?
3. Which files can I inspect for verficiation?

Here are some information about this problem. Thank you for your great help.

Joe

[joe@computer joe]# /sbin/ifconfig
eth0 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.120 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:676900 errors:0 dropped:0 overruns:0 frame:0
TX packets:781339 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
Interrupt:5 Base address:0x3000

eth0:0 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.121 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:1 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.122 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:2 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.123 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:3 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.124 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:4 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.125 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:5 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.126 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:6 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.127 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:7 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.128 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:8 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.129 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:9 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.130 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:10 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.131 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:11 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.132 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:12 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.133 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:13 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.134 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:14 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.135 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:15 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.136 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:16 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.137 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:17 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.138 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:18 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.139 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:19 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.140 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

eth0:20 Link encap:Ethernet HWaddr 00:50:8B:E0:37:04
inet addr:202.85.1.141 Bcast:202.85.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:5 Base address:0x3000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:60109 errors:0 dropped:0 overruns:0 frame:0
TX packets:60109 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0

[joe@computer joe]# netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
202.85.1.0 0.0.0.0 255.255.255.0 U 40 0 0 eth0
127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
0.0.0.0 202.85.1.1 0.0.0.0 UG 40 0 0 eth0

[joe@computer joe]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
202.85.1.0 * 255.255.255.0 U 0 0 0 eth0
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
default 202.85.1.1 0.0.0.0 UG 0 0 0 eth0

Hi Joe,

You do not need to list all your ifconfig again! Nothing is wrong with this configuration, but is is a bit goofy!!! In general, when you want to have a subnet you put it on a binary boundry, so your network administrator should really give you .128 - .160 (for a block of 32 addresses).

This way, the router which directs traffic to your subnet uses a netmast of 255.255.255.192

If you are the only machine running on the subnet you are running on a VLAN? If so, your network admin should give you a better block OR setup separate rules based upon address boundaries. Then, from outside the subnet you will have access.

BTW, in the future, you really should post what version of RH you are running ... thanx

HTH

Sorry for my inconvenience.

The IP range is assigned by data center. I will check further if there exists any problem there.

The server is based on RH7.1 at first but I recompiled the kernel and update almost all packages.