Add an alias IP on HP-UX

[Adam Garsha]

If I need to add an alias IP address on HP-UX, is this how I would do it (assume the card already has 2 other IP's attached) :

# (1) edit /etc/rc.config.d/netconf
# add these lines:

INTERFACE_NAME[3]=lan9:3
IP_ADDRESS[3]=X.Y.Z.A
SUBNET_MASK[3]=255.255.255.0
BROADCAST_ADDRESS[3]=X.Y.Z.255
INTERFACE_STATE[3]=up

# (2) attach the new IP manually (netconf is used at boot time)

ifconfig lan9:3 X.Y.Z.A netmask 255.255.255.0 up

[baiju_3]

Hi Adam Garsha,

You are Correct.

Thanks.
BL.

[Mel Burslan · Accepted solution]

Your assumptions are correct. Just make sure all your ip addresses are in the same subnet for this new virtual IP address to work.

[Adam Garsha]

Are you sure that the virtual IP's need to be on the same subnet?

[HGN]

Hi

What Lalb & Mel mentioned are true the important thing is that the IP has to be on the same subnet,hope you know this already.

Rgds

HGN

[Mel Burslan]

Think about it for a second. If it is not on the same subnet, how will the same physical network switch port is going to handle this IP address ? How will the packets coming out of this port will be routed ? And you will see the answer to your question yourself.

Very basic networking knowledge. No need to be a Cisco whiz.

[Adam Garsha]

Thanks all. What confused me is the documentation that stated you can have virtual IP's from multiple subnets attached to a single interface. I didn't stop to think how it would actually work.

Can you think of a reason why you would ever want or be able to make use of multiple subnetted virtual IP's attached to a single interface? If not, then should the tools stop you?

If you did alias a virtual IP from a different subnet to an interface that already contained multiple active/functioning virtual IP's from a single subnet what would happen?

Would all packets that go out the interface be hopelessly lost? i.e. no outgoing traffic? what would outgoing connections use for the source IP? the lowest lan9 IP or would they take on the higher lan9:3 IP for the source?

Very curious and sorry for asking dumb questions, I am just very curious.

[Adam Garsha]

If you did alias a virtual IP from a different subnet to an interface that already contained multiple active/functioning virtual IP's from a single subnet what would happen?

Would all packets that go out the interface be hopelessly lost? i.e. no outgoing traffic? what would outgoing connections use for the source IP? the lowest lan9 IP or would they take on the higher lan9:3 IP for the source?

Very curious and sorry for asking dumb questions, I am just very curious.