topic Set MTU in Operating System - HP-UX

Set MTU

Marcial Ruiz — Fri, 19 Mar 2004 10:47:20 GMT

How to set MTU in HP-UX 11.11?

I need to make tuning in Oracle NET.

example:

DB9I =
(DESCRIPTION =
(SDU=4096) ---> SDU = MTU
.
.
.
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)...
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = db9i)
)
)

Thanks

Re: Set MTU

RAC_1 — Fri, 19 Mar 2004 11:21:19 GMT

Though the MTU can be changed, you wont get any noticeable performance boost.

lanadmin -M is the command to user. You have to set it at both ends. i.e on nic and on switch/router side. The following thread explains this indetails.

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=202869

Anil

Re: Set MTU

RAC_1 — Fri, 19 Mar 2004 11:31:28 GMT

Check these threads also.

http://www.sun.com/solutions/blueprints/1002/817-0370-10.pdf

http://www.netapp.com/tech_library/3146.html#5.

Anil

Re: Set MTU

Ron Kinner — Fri, 19 Mar 2004 12:02:40 GMT

You can also use the route command to change the mtu on a static route to a particular host.

From: man route(1M)

/usr/sbin/route [-f] [-n] [-p pmtu] add [net|host] destination [netmask mask] gateway [count]

-p pmtu Specifies a path maximum transmission unit (MTU) value for a static host route. The minimum value allowed is 68 bytes; the maximum is the MTU of the outgoing interface for this route. This option only applies to adding a host route. In all other cases, this option is ignored and has no effect on a system.

Ron

Re: Set MTU

rick jones — Mon, 22 Mar 2004 13:31:14 GMT

If I am reading correctly between the lines, you want to try to alter the MTU of one of your NICs to 4096 bytes. There are only a few NIC types on which that is possible.

One is an 802.5 TokenRing network. Another is an ATM network. I suspect you have neither.

Another would be an FDDI network, or a HyperFabric network, but those already have an MTU > 4096 bytes.

That leaves Ethernet (well, for the most part).

It is not possible to have an MTU > 1500 bytes on a one-hundred or a ten megabit Ethernet network.

There is a non-standard (de jure) "Jumbo Frame mechanism one can use on Gigabit Ethernet, however, your switches and all the other nodes in your local IP subnet must support JumboFrames if you are to enable it.

As already pointed-out, you would use the lanadmin -M command.