multiple address for a LAN card

[Enrico Venturi]

Hello colleagues,
a simple question:
I knew that it's now possible (HP UX 11) to assign two or more addresses to the same LAN card:
where can I find more details on thi feature?
what's the MAN page?
moreover: when a message is sent from the local machine to a remote one, what is the IP address perceived by the remote machine? the main (if one)? ...?

Thanks a lot
Enrico

[melvyn burnard]

man ifconfig
The remote machine will still see this as the origional stationary hostname, unless you have an application that you can compile to bind with hte additional ip address.

[G. Vrijhoeven]

Hi Enrico,

There are several solutions.

One ( not supported if i am correct) is the ifconfig command ( man ifconfig) ifconfig lan1: netmask . ( multiple ip-addresses in same subnet ( switched) or HUP no ( different subnets).

Two, Install MC/SG ( supported) and let the clustersoftware ( man cmmodnet ) do it for you.

As for what IP adress i recieved. It would be the node ( MC/SG) ipadress and not the virtual ipadress. But this can depend on the config ( same networkid ).

Gideon

[Mark Grant]

The ifconfig route must be supported because that is pretty much what service guard does as far as I know.

ifconfig lan1:1 xxx.xxx.xxx.xxx netmask xxx.xxx.xxx.xxx

will give you a seconf IP address in lan1

[Fabio Ettore · Accepted solution]

Ciao Enrico,

you should search for "IP Multiplexing":

http://www.docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B3782-90716/B3782-90716_top.html&con=/hpux/onlinedocs/B3782-90716/00/01/135-con.html&toc=/hpux/onlinedocs/B3782-90716/00/01/135-toc.html&searchterms=ip%20multiplexing&queryid=20040126-041732

Just a link from docs.hp.com.
Also:

KBRC00010255 - Multiplexing Multiple IP's onto a Single Interface

Anyway the remote machine will perceived the configured IP address for that system in DNS, NIS or /etc/hosts file.

Best regards,
Ettore

[Todd Whitcher]

HP Customer Viewable Document id UTRANKBRC00011759

The official HP policy has been, that although the functionality may
work, that it is not supported. However, due to customer request, we now
provide this document. It describes the limited support and behavior
of multiple network interfaces that are configured into the same IP subnet via
the ifconfig command on HP-UX 11.X.

To summarize, this configuration is only supported for connectivity.

It is not intended for performance improvement or load balancing over multiple
interfaces; in that case the recommendation is to use Auto Port Aggregation
("APA") product.

Statement about support of multiple I/F configured with an IP address
belonging to the same subnet:

We certify that the TCP/IP stack will have the following behavior when
multiple interfaces are configured into the same IP subnet. Please note that
the use of multiple network interfaces configured into the same subnet via the
HP-UX Transport (ie via the HP-UX ifconfig command) is for connectivity
purposes to support interface testing and system management.

It is not intended for applications requiring more than one network
interface's worth of bandwidth.

1. Inbound traffic destined for a local IP address will be received on the
interface ifconfig'd with that IP address.

2. Outbound traffic to a next-hop destination IP address in the local subnet
will be sent out via the last interface ifconfig'd into that subnet.

3. Outbound traffic to destinations for which there is a specific host route
will use the interface specified by the route, regardless of the order in
which the interfaces are configured.

4. When ndd (HP-UX 11.x only) is used to enable the "Strong ES Model,"
applications which have bound to a specific local IP address and whose next
hop destination IP address is in the local subnet, will have their traffic
sent via the interface assigned that local IP address. Note, that in the
context of this discussion, the term "local IP address" refers to one of the
IP addresses assigned to an interface on a system with multiple interfaces
configured into the same IP subnet. "Next-hop destination IP address" refers
to the final destination IP address when that destination IP address is in the
same IP subnet, or the next-hop gateway IP address when the final destination
IP address is not in the same IP subnet.

Because of this limited support, HP still does not
recommend configuring multiple LAN cards on the same IP subnet.

[Enrico Venturi]

Todd,
Release Notes for HP UX 11.0 say that IP's can belong to the same subnets or to different subnets, moreover the feature seems to be officially supported...
What's the real situation?
And where can I find the documents whose identifier is provided?

[Todd Whitcher]

The Document I referenced is from HP's Labs. The document is available on the ITRC in the Technical Knowledge base, if your log on is linked to a Support Contract. Seach by document id and enter UTRANKBRC00011759.

The document provides the details regarding how the network behaves when multiple IP's are on the same subnet.

Hope that helps.

[Todd Whitcher]

The configuration is supported, the document I referenced describes the behavior. Its supported for connectivity, not load balancing. And you have to be aware of how the routing will behave.

Todd