Re: [CentOS] Basic Network question pinging different subnets

Bob Metelsky wrote:

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

so you have two seperate networks? the eth0's are connected to one hub or switch, and the eth1's to another hub or switch?

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,

presumably, the windows machine is connected to the 'eth0' network that the centos machines are connected to?

how exactly do you expect the packets to get from there to the other network? the windows machine has been instructed to forward all unknown packets to 10.54.7.1, which presumably is some other sort of router... chances are, said 10.54.7.1 has no clue where 10.54.0.xxx is.

solution 1) configure a linux computer to do 'ip forwarding', and give the windows machine a route like...

C> route add 10.54.0.0 mask 255.255.255.0 gw 10.54.7.2

or, solution 2) configure the router at 10.54.7.1 to have a route to this other network.

if both networks are on the same hub/switch, then I can only ask... WHY?