The built in Broadcom 5704 rev3 on my Tyan S2882 is brought up with MTU 1500 even after this change: # cat /etc/sysconfig/network/ifcfg-eth-id-00:e0:81:28:c7:b8 BOOTPROTO='dhcp' MTU='9000' REMOTE_IPADDR='' STARTMODE='onboot' UNIQUE='t2XO.naPqmzBs9CA' _nm_name='bus-pci-0000:02:09.0' # dmesg | fgrep tg3 tg3.c:v2.9 (March 8, 2004) tg3: eth0: Link is up at 1000 Mbps, full duplex. tg3: eth0: Flow control is on for TX and on for RX # uname -a Linux tyan 2.6.5-7.108-smp #1 SMP Wed Aug 25 13:34:40 UTC 2004 x86_64 x86_64 x86_64 GNU/Linux # lspci -v ... 0000:02:09.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5704 Gigabit Ethernet (rev 03) Subsystem: Broadcom Corporation: Unknown device 1644 Flags: bus master, 66Mhz, medium devsel, latency 64, IRQ 24 Memory at fc8a0000 (64-bit, non-prefetchable) [size=fc880000] Memory at fc890000 (64-bit, non-prefetchable) [size=64K] Expansion ROM at 00010000 [disabled] Capabilities: [40] Capabilities: [48] Power Management version 2 Capabilities: [50] Vital Product Data Capabilities: [58] Message Signalled Interrupts: 64bit+ Queue=0/3 Enable ... # ifconfig eth0 eth0 Link encap:Ethernet HWaddr 00:E0:81:28:C7:B8 inet addr:192.168.1.4 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::2e0:81ff:fe28:c7b8/64 Scope:Link UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1 RX packets:13696 errors:0 dropped:0 overruns:0 frame:0 TX packets:15444 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:6617183 (6.3 Mb) TX bytes:1883195 (1.7 Mb) Interrupt:24