Having atm and fe I wanted the latter to serve as a backup in case atm fails. So I configured atm to be .7 and fe to be .6 in the same subnet. It gave me a warning:
ifconfig (warning): route already exists (probably due to another interface on the same subnet.)
but that I (almost) expected.
However, when I test it and pull out the atm, fe doesn't respond to me (quite successfully destroying my concept of backup/load balancing/automounter).
That's not what I expected. Any thoughts?
p.
This is how all Network(TCP/IP) Drivers work I think, irrespective of the Operating system . I have seen such behaviour ( Though not with an ATM and Ethernet card, but with two Ethernet Cards.) on NT/Solaris too. Since the Network drivers sees two ports but both providing the same route, it just picks one route( probably the first in the routing table) and send packets on that. The second is not used at all, until someone from outside talks on that IP.
That is the reason I guess we have the concept of Virtual Interface...for backup, load-balancing etc...
Pramod
----- Original Message ----- From: "Piotr KUCHARSKI" chopin@sgh.waw.pl To: toasters@mathworks.com Sent: Saturday, May 04, 2002 5:29 AM Subject: two nics on same subnet
Having atm and fe I wanted the latter to serve as a backup in case atm fails. So I configured atm to be .7 and fe to be .6 in the same subnet. It gave me a warning:
ifconfig (warning): route already exists (probably due to another interface on the same subnet.)
but that I (almost) expected.
However, when I test it and pull out the atm, fe doesn't respond to me (quite successfully destroying my concept of backup/load balancing/automounter).
That's not what I expected. Any thoughts?
p.
On Sat, May 04, 2002 at 11:06:33PM +0530, Pramod wrote:
This is how all Network(TCP/IP) Drivers work I think, irrespective of the Operating system . I have seen such behaviour ( Though not with an ATM and Ethernet card, but with two Ethernet Cards.) on NT/Solaris too. Since the Network drivers sees two ports but both providing the same route, it just picks one route( probably the first in the routing table) and send packets on that. The second is not used at all, until someone from outside talks on that IP.
Ding, dong. To get your attention, I *was* trying to ping second interface after first got down (physically disconnected to be sure).
Hence I would rather see network driver notice interface down, remove all routes for this interface (which is probably done) and use another route (which is probably not done, as it was not added to routing table in the first place).
I could cheat with different network masks, I think. That is make one interface /24 (or /23) and second one /20 (all servers talking to filer would fit in that /24 or /23 and /20 is my whole network); that way it should pick more specific route first and if it fails -- the second, more general. Not ellegant, tho.
That is the reason I guess we have the concept of Virtual Interface...for backup, load-balancing etc...
Yes. But let's assume I need that setup for a while. :)
p.
-
Piotr KUCHARSKI -
Pramod