multicast routing

[Luca Rasconi]

Hi all,
for you this could be correct (from netstat -rn):
224.0.0.0 10.196.80.1 U 0 lan3 1500
224.0.0.0 10.196.81.1 U 0 lan4 1500
224.0.0.0 10.196.66.1 U 0 lan2 1500

thank you
Luca

[Adam J Markiewicz]

Hi

HP-UX do not like the same subnet over separate NICs.
It can look like working correctly at the beginning, but then you can find strange behaviour.

Check this:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x64e0cdec06f1d61190050090279cd0f9,00.html

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x94b83a1c04ffd61190050090279cd0f9,00.html

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x97689c196a4bd71190080090279cd0f9,00.html

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x330f5fe8b250d71190080090279cd0f9,00.html

Good luck
Adam

[Luca Rasconi]

The NICs are lan2, lan3 and lan4.
But I don't see a same subnet over this three NICs.
I see the same net destination routed over three different NICs.
I ask if I sent a packet to 239.1.13.16, belonging to that network, what is the NIC used? And why?
How OS works in this situation?

Luca

[Adam J Markiewicz]

Hi again

The subnet:
To be absolutelly sure you should check netmask also (netstat -nrv).
If you used the default, the 10.x.x.x is address of class A, fo these three are in the same subnet 10.0.0.0

Good luck
Adam

[Luca Rasconi]

In according with the netmask (now i can't supply), i can say that lan2,3 and 4 are in different subnet.

Luca

[Ron Kinner]

It's not clear what you are asking. As others have pointed out having more than one nic in the same subnet on an HPUX tends to cause problems and should be avoided.

As far as 224 is concerned this is a special case and having a route to 224 on every interface is normal. See the man for mrouted where it says:

"mrouted automatically configures itself to forward on all multicast-capable interfaces (i.e., interfaces that have the IFF_MULTICAST flag set, excluding the loopback "interface")."

The network you cited, 239.x is not a member of the 224 network so the netstat info you gave does not apply.

Ron