Multiple Network Connections ?

[oqurum]

I have 2 10/100 ethernet adapters to configure in AIX but have been told that I cant assign addresses using the same subnet.
I have configure one adapter successfully but am loath to
configure the second until someone can explain why I shouldnt use the same subnet as the first.

 

[MikeLacey]

don't see why you shouldn't use the same subnet for both,

what would be the implications if you crashed your AIX box? is it a live machine? If it's a test box I would try it Mike
michael.j.lacey@ntlworld.com
Email welcome if you're in a hurry or something -- but post in tek-tips as well please, and I will post my reply here as well.

 

[eTTan]

You can have multiple ip addresses on the same box and on the same subnet, but you can only have one default gateway.

/eMaCs

 

[Guest_imported]

I've tried this and you will only get one card to talk on the same subnet - great idea for reduncy purposes that won't work. Why do you want to put the two cards on the same subnet?

 

[oqurum]

I shall define the second line on another subnet I think

Thank you all for your help

 

[PSD]

oquorum,

You will need to explicitly use a different subnet on the second adapter if you wish to use that particular card for communication. In routing if you have two cards both on the same subnet all traffic to that subnet will go via the first adapter in the routing table list i.e. netstat -rn
this means the second card will not be used, to get around this you retain the same subnet mask but change the logical subnet. This is done in HACMP configurations when you have IP failover as part of checking HACMP needs to explicitly be able to ping inidividual cards to distinguish between a network and network card failure.

Hope that helps

PSD
IBM Certified Specialist - AIX V4.3 Systems Support
IBM Certified Specialist - AIX V4 HACMP

 

[mikeabest]

When you have multiple adapters you have what is called a "multi-homed" system. i.e. it just like a person having two phone numbers and all of the implications trying to reach that person.

Why do this? It is nice to use one NIC for the NET and another for the LAN.

I specialize in Pick mvVALUE sites where administrion is minimized because my clients want their resources directed to the APPLICATION. So I regularly use multiple adapters to physically segment the network...LAN, WAN, NET, MODEM BANK, TERMINAL SERVERS, HOT BACKUP and so forth.

If you wish to talk across the segments then the appropriate gateways and static routes must be set up.

I only found a few individuals that really understand how to do this. But it is nice when done. This is essentially a networking issue. AIX will NOT handle dual NICs on the same subnet automatically, in fact it will probably take both subnets out of service, Windows does a much better job of hiding the housekeeping from the administrators.