network problem with eth0 on linux

[esolve]

I have a laptop, the wifi is OK, but for wired network, if I'm using windows, it is OK. But with linux, yesterday, it is OK, but today I can't access the network through eth0(in windows, it is OK), what are potential problems?

BTW, yesterday I modified MTU from 1406 to 500, but then modified it back to 1406.

eth0 Link encap:Ethernet HWaddr 5C:26:0A:2B:B8:06
inet addr:138.96.201.72 Bcast:138.96.207.255 Mask:255.255.240.0
inet6 addr: fe80::5e26:aff:fe2b:b806/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1406 Metric:1
RX packets:21221 errors:0 dropped:0 overruns:0 frame:0
TX packets:1355 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:3710568 (3.5 MiB) TX bytes:130299 (127.2 KiB)
Interrupt:20 Memory:f5400000-f5420000

additional information: 1 it seems it is from dhcp coz I didn't do any configuration for the ip address, and it is a public IP. but the ip is fixed

2 I think the /etc/resolv.conf is fine, coz previously the network is fine

[Miven]

OK. I'm no network guru or anything, but I do know that playing with ifconfig is for network gurus *only*. Any changes you make there affect all your communications and everything around you.

My best guess? I think you've confused your router and other things by tweaking your MTU. Now it thinks your PC speaks Martian Dialect #43 with a stuttering lisp, and it's deliberately ignoring you.

If you're going to play around with a network interface, get a 2nd NIC and play with that, so you don't get a crippled primary interface.

I hope someone else has some more constructive advice.

BTW my MTU is 1500.

Peace and cheer.

[Lazydog]

1. Is your setup running static IP or DHCP?
2. If static what is your IP ADD and MASK
3. IF DHCP what is your IP
4 Post the output from 'route -n'