[CentOS] Routing issue between 2 LANs

Sun Dec 19 18:15:33 UTC 2010
Jose Maria Terry Jimenez <jtj at tssystems.net>

El 19/12/2010, a las 19:01, Les Mikesell escribió:

> On 12/19/10 11:07 AM, Jose Maria Terry Jimenez wrote:
>> Hello All
>> First, sorry by my poor english, hope you understand me :-)
>> I have a problem, i don't understand or don't know how to solve
>> I need to interconnect 2 networks with different numbers. One is
>> the other Mainly i need to access services in
>> the 236. from the 1. one.
>> I have a CentOS 5.5 machine with 2 nics each one configured to work in one of
>> the nets. The CentOS also uses a router for Internet access that is
>> >-----[CentOS Machine]-- --------<
>> So, i enable forwarding in the CentOS box
>> echo '1' > /proc/sys/net/ipv4/ip_forward
>> And in one machine of the 1. network (this is Fedora14) I add the route:
>> route add -net netmask gw dev eth0
>> Since this moment i can ping or access (ssh/http) another CentOS machine in the
>> 236 network
>> ping
>> PING ( 56(84) bytes of data.
>> 64 bytes from icmp_req=1 ttl=64 time=0.281 ms
>> But can't access or ping other machines (NOT Linux ones), ie, printers, Win
>> servers, etc...
>> Also tried adding:
>> route add eth0
>> before the route add -net, but no efect.
>> This fails even if i flush IPTables.
>> In the CentOS box that replies, i did nothing, it 'just' works.
>> Can anyone tell what is happening / help me with this?
>> Something to do missing in the CentOS router that joins the networks?
> First make sure that you can ping/access those 'other' services from the centos 
> box with 2 nics.   It should source from the .236 interface and 'just work'.  If 
> not, you have firewalls or something else blocking traffic.   When you route 
> other traffic from the .1 network, the destination machines need some reason to 
> send the return packets to the address.  You can either add the 
> route to every machine or on the router that is currently their default router.
> -- 
>   Les Mikesell
>      lesmikesell at gmail.com

Thank you Les,

Yes, i can ping/access those 'other' services from the CentOS box with 2 NICs.

I understand that i need, for example in a networked printer in 236. network a 'return' route. I definitely have no access to configure network on every machine in the 236 network (only a few), nor the router...

This can't be solved any other way?