In your case I would go with your network guy. I have had both situations with no difference in speed or reliability. Not every case is the same though, it depends on the combination of switch and nics. So set it all to fixed speeds and see how it goes.
If it doesn't work, you have to tell the network guy to set the switch to auto and you will have to set your nics of course to auto too.
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Generally, best practices is to force speed and duplex with 10/100 NIC's but leave GIG nics to AUTO. Least that's what the in-house CCIE has been preaching at me for years =)
With gigabit it is always recommended to go Auto/Auto, with 100MB the recommendation was 100/Full.
The standard for 1000BASE-TX requires autonegotiation to be always present and enabled. Other than speed and duplex mode, autonegotiation is used to communicate the port type (single port or multiport) and the master-slave parameters (whether it is manually configured or not, whether the device is master or slave if this is the case, and the master-slave seed bit otherwise).
Here's the technical mumbo jumbo:
The IEEE 802.3 standard states that you must support and test autonegotiation
enabled to certify a product IEEE 802.3 compliant, and for multivendor
interoperability (for example, testing at the UNH Interoperability Laboratory). There
are no requirements in the standard to support locked down or forced configurations
using autonegotiation disabled. As a result, there are no requirements for vendors to
test multivendor interoperability between products with autonegotiation disabled.
The IEEE 802.3ab specification does not allow for forced mode 1000BASE-T with
autonegotiation disabled running at 1000 Mbps. As a result, many switch vendors do
not support forced mode. Although the transceiver used in the Sun Gigaswift
Ethernet UTP adapter 1.0 is configurable for the 1000 Mbps forced mode and the ce
driver allows this mode be aware that it does not work under certain circumstances.
Clause 40 (1000BASE-T), subclause 40.5.1 of 802.3 states:
All 1000BASE-T PHYs shall provide support for Auto-Negotiation
(Clause 28) and shall be capable of operating as MASTER or SLAVE.
Auto-Negotiation is performed as part of the initial set-up of the link, and
allows the PHYs at each end to advertise their capabilities (speed, PHY
type, half or full duplex) and to automatically select the operating mode
for communication on the link. Auto-negotiation signaling is used for the
following two primary purposes for 1000BASE-T:
a) To negotiate that the PHY is capable of supporting 1000BASE-T half
duplex or full duplex transmission.
b) To determine the MASTER-SLAVE relationship between the PHYs at
each end of the link. 1000BASE-T MASTER PHY is c from a local source.
The SLAVE PHY uses loop timing where the clock is recovered from the
received data stream.
What this means is that although autonegotiation (Clauses 22 and 28) is optional for
most variants of Ethernet and manual configuration (forced mode) is allowed, this is
not the case for Gigabit copper (1000BASE-T). Per the IEEE 802.3u specification, it
not possible to manually configure one link partner for 100 Mbps full duplex and
still autonegotiate to full duplex with the other link partner. In all cases, both ends
of the link must be set to the same value or the link may not connect or may
result in duplex mismatch as shown in following tables.
If you want to read the whole doc:
Generally, best practices is to force speed and
duplex with 10/100 NIC's but leave GIG nics to AUTO.
This is the same as we do it...