[CentOS] Re: Basic Network question pinging different subnets

on 11/16/2007 4:25 PM Bob Metelsky spake the following:

Hi Im a little perplexed by this situation

I have centos 4.5 installed on 2 pcs - each with 2 network cards

machine 1

eth0 Link encap:Ethernet HWaddr 00:14:2A:6B:C8:CC inet addr:10.54.7.2 Bcast:10.54.7.255 Mask:255.255.255.0 eth1 Link encap:Ethernet HWaddr 00:11:50:9B:A2:90 inet addr:10.54.0.2 Bcast:10.54.0.255 Mask:255.255.255.0

machine 2

eth0 Link encap:Ethernet HWaddr 00:14:2A:69:4C:47 inet addr:10.54.7.3 Bcast:10.54.7.255 Mask:255.255.255.0

eth1 Link encap:Ethernet HWaddr 00:11:50:9B:A5:0A inet addr:10.54.0.3 Bcast:10.54.0.255 Mask:255.255.255.0

machine 1 & 2 can ping each other on either subnets

machine 3 (windows)...

C:>ipconfig

   Connection-specific DNS Suffix  . :
   IP Address. . . . . . . . . . . . : 10.54.7.16
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 10.54.7.1

cant ping anything on the 10.54.0 subnet, nor does that subnet show up ip using a port scanner...

C:>ping 10.54.0.2

Pinging 10.54.0.2 with 32 bytes of data: Request timed out. Request timed out.

C:>ping 10.54.7.2

Pinging 10.54.7.2 with 32 bytes of data: Reply from 10.54.7.2: bytes=32 time<1ms TTL=64 Reply from 10.54.7.2: bytes=32 time<1ms TTL=64

Any ideas why this is happening? I dont have a firewall on the 10.54 address,

Machine 3 is locked to its subnet by the subnet mask. Your above mask of 255.255.255.0 only lets the windows machine talk to 10.54.7.1 through 10.54.7.254. Without adding a route to that other address, or a virtual IP address in that address space, the windows machine can't see or communicate on the other subnet.