[wellylug] Route Tables + Question + I Hope I explain this...

[Enkidu]

I think trying to route stuff to the gateway and then back in is
fraught with problems. Why not set up DNS inside?

Cheers,

Cliff

On Fri, 04 Jun 2004 20:31:28 +1200, you wrote:

>My routing question .... Trying once again! :)
>
>We have domainname.com pointing to ip address 1
>We have lists.domainname.com point to ip address 2
>Both those IP addresses are on the same router box, and IP address 2
>gets forwarded to penny 192.168.0.68 - well port 80 and 25 do anyway by a firewall and NAT.
>Any URL requests get munged by Squid and on forwarded to penny as well and returned to the requesting client.
>
>Anyone who trys and connects inside the company to
>lists.domainname.com gets the DNS entry as an outside address - ip
>address 2, because we dont have a DNS server inside the company that
>serves up domainname.com domain names so it will never find the internal ip of the machine....
>
>So what happens is example jenna 192.168.0.15 pings, lists.domainname.com and DNS resolves to 
>ip address 2  - packets go outside the company, and back in side the
>company by the router / firewall / squid and get forwarded on to penny.
>Just like as if they were requesting over the internet.
>
>If the routing table on penny stays standard, IE 
>192.168.0.0        *	blah blah blah eth0
>default     192.168.0.33 blah blah blah eth0
>
>The packets get stopped by penny her self. by what we can see with tcpdump
>If I remove the route 192.168.0.0    * blah blah blah eth0 
>and just leave the default route in, then it works both inside and
>outside the company.
>
>It's been sujested that Debian may have some anti-spoofing filter or
>something either in the kernel or somewhere else that is dis-allowing
>the traffic flow...
>
>I have seen in /etc/network/options a spoofing option, to which I have
>changed from N to Y or from Y to N.. and restarted the network
>interface, to encounter the same problem.
>
>Its very long winded and probabally didnt explain there very well either
>:)
>
>On Fri, 2004-06-04 at 19:06, Enkidu wrote:
>> On Fri, 04 Jun 2004 11:45:55 +1200, you wrote:
>> 
>> >Hello, 
>> >
>> >I hope I explain this correctly -- 
>> >
>> >OK.....
>> >
>> >I have a machine, it has a DNS entry for an external IP address that is
>> >different from archnetnz.com, for the purpose of this, we will call it,
>> >lists.archnetnz.com
>> >
>> OK, is it *physically* external or internal? What device seperates
>> internal from external networks?
>> >
>> >When you ping lists.archnetnz.com from within the local network it
>> >resolves the external IP address - via the default route, which is what
>> >we want....  archnetnz.com is not the internal network suffix nor is
>> >there an internal DNS server hosting up .archnetnz.com names....
>> >
>> I just plain don't understand this. When the DNS resolves a Domain
>> name to an IP address the route doesn't come into it. When you ping
>> you either get a packet back or not. How do you know what route the
>> packet takes? Did you use traceroute?
>> >
>> >The Ping comes back in via that same default router and it sends it off
>> >to the machine in question through a static route.
>> >
>> How do you know what route the packet comes back from?
>> >
>> >This is the routing table of the machine in question - -and it works.
>> >
>> >It will connect internally on the network to the external IP address,
>> >and obviously from external to the external IP, for what the static
>> >route exists for forwarding all packets to lists.archnetnz.com's ip
>> >address to it's internal IP address.
>> >
>> >ONLY IF THE ROUTE TABLE ON THE MACHINE LOOKS LIKE THIS!
>> >
>> >penny:/etc/network# route
>> >Kernel IP routing table
>> >Destination  Gateway       Genmask   lags Metric Ref Use Iface
>> >default    192.168.0.33    0.0.0.0   UG    0      0   0  eth0
>> >
>> >But if it looks like this:
>> >
>> >penny:/etc/network# route
>> >Kernel IP routing table
>> >Destination  Gateway       Genmask    lags Metric Ref Use Iface
>> >192.168.0.0    *         255.255.255.0 U   0      0   0  eth0
>> >default    192.168.0.33    0.0.0.0   UG    0      0   0  eth0
>> >
>> >Which is the standard route when the interface comes up, it does not
>> >route the packets correctly from internal to the external IP address.
>> >
>> What is .33? Is it your router?
>> >
>> >Now I hope I have explained it correctly, if you need further
>> >clarification on anything please let me know, and I will be happy to
>> >provide any further info regarding this :)
>> >
>> >Thanks...
>> 
>> Cheers,
>> 
>> Cliff
>--