pinging from multihomed server

[sergio becerra]

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

 

[Phillip Windell]

If i want to ping from the server to router 192.168.1.1 , what NIC will gene
rate the icmp packet?

The one you pinged gets it.

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.

The originating NIC,... when pinging from a multi-homed machine,...will
always be the nic associated with the route in the Routing Table. It is just
that simple. It is not somehting that you can "control".

 

[DS]

(e-mail address removed) (sergio becerra) wrote in

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