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

Enkidu enkidu at cliffp.com
Fri Jun 4 19:06:32 NZST 2004


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




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