[CentOS] Routing issue between 2 LANs

José María Terry Jiménez jtj at tssystems.net
Mon Dec 20 21:02:20 UTC 2010


Andrej Moravcik escribió:
> Hello Jose,
>
> from the picture you provided the situation looks pretty simple.
>
> - you have enabled IP forwarding on router, I recommend you to put it 
> into /etc/sysctl.conf for persistence.
>
> - you have configured firewall rules on router to allow forwarding 
> traffic from left to right subnet. You can also try to set up ACCEPT 
> policy just for testing.
>
>
> - the default gateway for left subnet is 192.168.1.1 (you mentioned 
> router for Internet access). Correct me if I'm wrong.
>
> - the default gateway for right subnet I assume is 192.168.236.74. You 
> don't have to do anything with routing here. Every host in right subnet 
> knows where to send replies.
>
>
> - the problem seems to be missing routing information in left subnet. 
> Hosts don't know anything about the right subnet and thus send requests 
> to the default gateway 192.168.1.1.
>
> - modifying routing table on every host in left subnet can be solution 
> in case, if there is only a few hosts which need to access right subnet
>
> - if you need to have fully accessible subnets, put the static route to 
> default gateway 192.168.1.1 to redirect requests to proper gateway. If 
> it is Linux gateway, try something like this
>
> [root at default-gw]# ip route add 192.168.236.0/24 via 192.168.236.74
>
>
> Regards
>
> Andrej
>
>
>
> Jose Maria Terry Jimenez wrote:
>
>   
>> 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 192.168.1.1.
>>
>> 192.168.1.0/24 >-----192.168.1.100--[CentOS Machine]--192.168.236.74 
>> --------< 192.168.236.0/24
>>     
>
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>   
Thank you very much, Andrej.

Today i couldn't test this, but default gateway for right subnet is 
192.168.236.21 and i can't change anything in that router and many 
machines of that network, i only admin a few there.

Best,


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