HP-UX System Administrator's Guide: Configuration Management

2. Test the card and link with nwmgr, as follows:
# nwmgr -c lanPPA -A link_state,speed
For example,
# nwmgr -c lan0 -A link_state,speed
lan0 current values:
Link State = Up
Speed = 1 Gbps Full Duplex (Autonegotiation : On)
The Speed line includes the current speed, the current duplex setting, and how the
setting was determined.
If the last item says Autonegotiation : On (as above), this indicates you have set
the card to auto_on and the card determines the correct setting. On Fast Ethernet
links, this is only appropriate if the switch port is also in auto_negotiate mode. It
will not work properly if the switch is hard set to 100FD. If you see something like:
Speed = 100 Mbps Half Duplex (Autonegotiation : On)
(note the Half Duplex) then it almost certainly means that the switch is hard set to
100FD. In this case, you will encounter collisions and dropped packets and potentially
poor network performance or even see the switch disable the network port due to a
(perceived) high error rate.
If you see:
Speed = 100 Mbps Full Duplex
(note the missing (Autonegotiation : On)), it means that your card is hard set to
100FD and is not autonegotiating. In this case, the switch must also be hard set or you
will see errors as noted above.
HP recommends the settings shown in Table 9-1 (page 140). For 100Mb/s links, setting
one side of the link to autonegotiate and the other hard set to 100FD will cause
connectivity problems. Always verify that the switch setting is the recommended one
used across your site (such as 100FD).
Configuring Optional Jumbo Frames Size for Gigabit Ethernet
(Jumbo frames are supported only at 1000 Mb/s)
• Jumbo frames for the iether and igelan drivers have a maximum transmission
unit (MTU) in the range 1501 to 9000 bytes. Normal frames on have an MTU in
the range 256 to 1500. If you are using Jumbo Ethernet frames, ensure that:
— All end stations on a given LAN have the same MTU setting;
(In the Jumbo Frames description, “LAN” means that the end stations do not
have any routers or layer 3 switches between them.)
— Intermediate stations such as switch ports in your LAN have an MTU equal to
or greater than the end station’s MTU.
• Obtain the PPA number of the card by entering nwmgr.
Ethernet Configuration and Verification 141