FDDI to Ethernet conversion

[Rachid Abrahin neto]

Hello folks,

we've had to change the NIC's in one of our servers,
and exchanged one FDDI interface for two 10baseT
others. Things ran like this:

- We had MC/Service Guard running in the host server,
but given the host would not be part of a cluster
anymore we made one of the 10baseT interfaces act
with the same IP address that the former FDDI used to,
and applied the MC/Service Guard "package" to the
second NIC. This would share load between these
addresses (one of them is more often used for terminal
applications and the other is related to our database
services).

- However, since we made this change, things have
become really weird. The transfer rate to *any* of
the interface (through an FTP session, for instance)
has become so slow that sometimes it seems like we're
in a dial-up link.

Any comments would be very appreciated. One of HP
technicians told us that it is not possible having
two IP addresses to a same CPU in HP-UX 10.20, but
this information seems not to make sense.

Thanks in advance for any help,
Rachid Abrahin
Rio de Janeiro - Brazil

[Berlene Herren_1]

This is true, having two IP addresses, the same or on the same subnet, is not
supported until 11.0 with APA, and will cause problems. I attached a document
that may explain why.

berlene

[Peter Mchale]

Hello,

Apart from the important fact that each card should be on seperate subnets you
do not say where you are ftp'ing from or to.
If you are trying to ftp between one subnet on a 10meg card and another subnet
on fddi then there may be ip fragmentation affecting your systems performance.
On a 9000 if you run:

netstat -ni

You see a table showing the interfaces and there respective mtu sizes.
Ethernet is normally 1500 bytes whereas fddi is 4352. If taking data from fddi
to ethernet then the packets will be fragmented (chopped up) and then
re-assembled, ie, chopped down from 4352 to 1500 and then rebuilt. It may be
possible to reduce the fddi mtu size however this would affect all packets
leaving through that interface.