Re: pinging from multihomed server

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From: DS (t.h.i.s.n.t.h.a.t_at_a.d.e.l.p.h.i.a..n.e.t)
Date: 09/08/04 

Date: 7 Sep 2004 21:34:59 -0500

sat@nivel8.com (sergio becerra) wrote in
news:cfa9cca3.0409062224.29e5df1b@posting.google.com:

> Hi,
>
> Imagine this situation:
>
> Windows 2000 server multihomed:
>
> nic1 (external->subnet 192.168.1.x)
> ip: 192.168.1.10
> mask: 255.255.255.0
> DG : 192.168.1.1
>
> nic2 (internal->subnet 192.168.16.x)
> ip : 192.168.16.1
> mask: 255.255.255.0
>
> routing is enabled
>
> The router in 192.168.1.1 has a static route to send back packets to
> subnet 192.168.16.x
>
> If i want to ping from the server to router 192.168.1.1 , what NIC
> will gene rate the icmp packet?
>
> Do I have a way to force it ?imagine just you want to check if the
> ping if g oing from 192.168.16.1 rather than 192.168.1.10 - without
> using traffic moni tors to capute packets.
>
> I know i could telnet to 192.168.1.1 and try to ping from the router
> to 192. 168.16.1 BUT just need a way to verify the originating NIC in
> ping commands on multihomed server.
>
> thanks in advance
> sincerely

Very simply, when a computer needs to send a packet to a destination
address, it first checks to see if the destination is on a local subnet.
If it is, it will send it out that local subnet interface.

If it is not, it will send it out the default gateway to be forwarded by
whatever device the g.w. is.

Therefore, a multi-homed PC, 192.168.1.x & 192.168.16.x, will send all
packets destined for the 192.168.16.x subnet directly out that interface.
All other packets should be sent from the 192.168.1.x subnet, since that
is where the gateway is attached.

DS

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