Networking help

[pll at lanminds.com]

In a message dated: Tue, 17 Dec 2002 09:33:55 EST
Bob Bell said:

>> However, let's assume 'T' did exist.  So what?  IMO, the icmp packets
>> should never have gone to 'T' anyway.  Shouldn't have gone back out
>> the interface they came in on?
>
>    I was going to reply, but I think Ben already answered this adequately:
>
>  No!
>
>  ****** IP routing is a stateless operation. ******

I was about to state that there was a better route for the echo 
reply, that being the interface the packet came in on.  Then it 
dawned on me why I persist in believing this.  I was ignoring the 
fact that the echo request was coming from a completely different 
network than either of the configured interfaces was connected to.

My mistake was thinking that the request came in on the 10.241.38.0 
interface (eth1), and therefore, given a routing table of:

  Kernel IP routing table
  Destination  Gateway       Genmask        Flags  MSS Window irtt Iface
  10.241.38.0  0.0.0.0       255.255.255.0  U      40  0        0  eth1
  192.168.10.0 0.0.0.0       255.255.255.0  U      40  0        0  eth0
  0.0.0.0      10.241.38.1   0.0.0.0        UG     40  0        0  eth1
  0.0.0.0      192.168.10.1  0.0.0.0        UG     40  0        0  eth0

that it would match the first route for 10.241.38.0 and go out eth1.  
However, the reply wasn't destined for this subnet at all, and 
therefore had to match one of the default 0.0.0.0 entries (which is 
where things probably got all messed up!)
-- 

Seeya,
Paul
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