[CentOS] Routing issue between 2 LANs

Jose Maria Terry Jimenez jtj at tssystems.net
Sun Dec 19 19:45:11 UTC 2010


El 19/12/2010, a las 20:34, Les Mikesell escribió:

> On 12/19/10 12:31 PM, Jose Maria Terry Jimenez wrote:
>>>> 
>>>> 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 192.168.236.74 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?
>>> 
>>> Best
>> 
>> Hello Again,
>> 
>> I forgot:
>> I made a mistake in my original post, the ping is to a diferent CentOS box in the 236. network (192.168.236.80) and it replies and i can access it from the Fedora machine in the 1. net.
>> 
>> Why the other CentOS box (in the 236. net) works (reply, can be accessed) without adding any route?
>> 
>> The Fedora box (1. network):
>> [jose at IDi ~]$ ping 192.168.236.80
>> PING 192.168.236.80 (192.168.236.80) 56(84) bytes of data.
>> 64 bytes from 192.168.236.80: icmp_req=1 ttl=64 time=1.61 ms
>> 64 bytes from 192.168.236.80: icmp_req=2 ttl=64 time=0.684 ms
>> [jose at IDi ~]$ ifconfig eth0 | grep -i 'inet addr'
>>           inet addr:192.168.1.3  Bcast:192.168.1.255  Mask:255.255.255.0
> 
> This doesn't make much sense without a route.  Can you try a traceroute to the 
> fedora box address from the 192.168.236.80 box to see how/why it gets there?

Sure, here it is:

From fresh reboot of the Fedora14 box:

[jose at IDi ~]$ su -
Contraseña: 
[root at IDi ~]# route add -net 192.168.236.0 netmask 255.255.255.0 gw 192.168.1.100 dev eth0
[root at IDi ~]# logout

[jose at IDi ~]$ traceroute 192.168.236.80
traceroute to 192.168.236.80 (192.168.236.80), 30 hops max, 60 byte packets
 1  puente (192.168.1.100)  0.286 ms  0.260 ms  0.239 ms
 2  192.168.236.80 (192.168.236.80)  0.963 ms !X  0.949 ms !X  0.930 ms !X
[jose at IDi ~]$ ping 192.168.236.80
PING 192.168.236.80 (192.168.236.80) 56(84) bytes of data.
64 bytes from 192.168.236.80: icmp_req=1 ttl=64 time=0.668 ms
64 bytes from 192.168.236.80: icmp_req=2 ttl=64 time=0.599 ms
64 bytes from 192.168.236.80: icmp_req=3 ttl=64 time=0.566 ms
^C
--- 192.168.236.80 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
rtt min/avg/max/mdev = 0.566/0.611/0.668/0.042 ms

[jose at IDi ~]$ ssh 192.168.236.80
jose at 192.168.236.80's password: 
Last login: Sun Dec 19 20:44:44 2010 from 192.168.1.3
[jose at control ~]$ 





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