[CentOS] Basic Network question pinging different subnets

Bob Metelsky bobmetelsky at comcast.net
Sat Nov 17 04:12:16 UTC 2007


Im a dba not a network guy... :)
Well.... ok I know there are technical "reasons" why this doesn't seem 
to "work"

But -  why can I ping any other ip address ....  ie Google
64.233.167.99

Ok I guess thats "resolvable" and not private. My thinking is ping 
should try and  "find" the address

Maybe I need a type of local dns...(??)  How does one avoid  manually 
adding "routes"

my port scanner - I give a range 10.54.0.0 - 10.54.7.55, Im thinking it 
should try all addresses in between and it only gets the ones on 10.54.7.0

The comment below sounds like what I need... thanks!

"

c:\> route add 10.54.0.0 MASK 255.255.255.0 10.54.7.16

But this should give you access on both 10.54.0.2 and 10.54.0.3

"

C:\>route add 10.54.0.0 MASK 255.255.255.0 10.54.7.16

C:\>ping 10.54.0.2

Pinging 10.54.0.2 with 32 bytes of data:

Reply from 10.54.0.2: bytes=32 time<1ms TTL=64
Reply from 10.54.0.2: bytes=32 time<1ms TTL=64

My purpose is to have a private network between database servers (oracle 
rac) where only specific traffic is allowed, and it works that way, I 
was just surprised that I want able to ping the 0 subnet.
So I need to add the route...

Thanks for everyones feedback. Hopefully I can contribute 
something....in the future
;-)

Bob




Alain Spineux wrote:
> On Nov 17, 2007 1:25 AM, Bob Metelsky <bobmetelsky at comcast.net> 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
>>
>> 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,
>>     
>
> Yes ! You have to learn how works IP networks :-)
> IP is wild and wide :-)
>
> you can try this on your windows :
>
> c:\> route add 10.54.0.2 MASK 255.255.255.255 10.54.7.2
>
> OR
>
> do the same on your router at 10.54.7.1
>
> OR (depend on how your linux box is configured)
>
> c:\> route add 10.54.0.0 MASK 255.255.255.0 10.54.7.16
>
> But this should give you access on both 10.54.0.2 and 10.54.0.3
>
> OR if routing is enable on 10.54.7.2
>
> c:\> route add 10.54.0.0 MASK 255.255.255.0 10.54.7.2
>
> should also give you access to both 10.54.0.2 and 10.54.0.3
>
>
> You just have to understand the first one other are just to spread out
> my IP knowledges.
> Ops, the last one is sometime useful to configure a device on another
> IP range, without reconfiguring your IP.
> Like when unpacking a new router with IP 192.168.123.1
>
> Regards.
>
>
>   
>> Thanks
>> Bob
>>
>>
>>
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>>
>>     
>
>
>
>   
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