Hello,

i have a WRT54gs and i have problems to serve any websites.
firmware openwrt54gs-v4-squashfs

Every port is his own vlan

internet port = vlan 0
port 1 = vlan1
port 2 = vlan2

etc

the mtu of the ppp0 interface is 1492 an in the nvram variables the ppp_mtu=1492

the router connect to my provider with no problems. i can ping with a package size of 1492 all websites, but when i ping from a workstation behind a vlan interface i can't ping with a package size of 1492.
Because when i ping normal i can reach all websites.

what kind of problem is that, please help.

Sorry my english is not good.

If you're tagging you need mtu 1496 to allow for tag.

- DL

the mtu size of the vlan interfaces or the mtu of the ppp0 interface ?

I have bridged eth1 with vlan1 to br0. ( br0 = port 1 )

thanks for your help.

had similar problem and found following work-around:
via regedit on the Windows PC go to the
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{some_key_code}    (try the various interfaces to find the one that connects to the openwrt box) and create two new DWORD entries
MTU 1492    (decimal)
TCPWindowSize 130000 (decimal, value not critical but should be in this magnitude)

Close regedit.
Make the new TCPIP configuration active for this interface by going to  'Network and Dial-up connections' and disable the interface and then enable it again. Now you should be on the net !

Would welcome hints how to cure this within OpenWRT, but the above works for me but it is a nuisance having to make the adjustment in every PC.

rgds, doddel

it really works but when i use my linux workstation the doesn't work.
I have use the command on my linux workstation

ifconfig eth0 mtu 1492

they doesn't work

I have a new firmware installed on my wrt54gs_v4 the jffs.bin file

I have no vlans to test the ping sizes.

the router goes online without probs. I can ping from the router any websites with any package sizes  ping freenet.de -s 1500  it works, but when i ping from a workstation behind the lan interface

on a windows prompt

ping freenet.de -l 1464    ->  works
ping freenet.de -l 1465    -> don't work

What is the problem of the openwrt Software ???

the problem is by the t-com server.
this server cannot reply the message fragment is needed.

the wrt must fragment the packages but they don't work, so i have set mtu sizes in the windows registry of the clients and in the linux workstations with ipconfig. this config works but you must configure this mtu in all client workstations.

thanks for help me

Sounds like the wrt is fragmentting just fine when you ping from it. Perhaps the fragment request ICMP packets (or mtu discovery packets) aren't getting forwarded to your workstations? Check your firewall rules on the wrt.

But in any case the probable source of the aggravation is that your ISP is probably running vlans over some equipment that won't handle normal ethernet MTU when tags are added on. I had a similar situation when I first started using vlans on our wireless network and had to replace a switch or two to eliminate it (or else do like you and set client MTU down).

Might it not fix it just to reduce the mtu on your wrt?

-DL

(Last edited by dl on 3 Jan 2006, 10:58)