vlan trunking problem [solved]

redbeardmcg · Posted: Sun Dec 03, 2006 5:08 am Post subject: vlan trunking problem [solved]

I currently have my linux router trunking 2 vlans (one for my internal network and one for my isolated wireless network). Everything works perfectly except when I try to upload something.

I can download at 2.0Mbps (fios is great), but trying to scp a file or do anything that needs upload bandwidth, the connection stalls. In fact, I could not even post this without placing my port on the external vlan on my cisco switch.

Here are my vlan configs

/proc/net/vlan/config:

Jeremy_Z · l33t Joined: 05 Apr 2004 Posts: 671 Location: Shanghai

My first guess is : MTU, VLAN requires extra info per packets, if your MTU is not set properly you will have this kind breakage.
Quick fix is : reduce MTU on your client.
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redbeardmcg · Posted: Sun Dec 03, 2006 10:36 am Post subject:

Is that something I can do at the switch level, or does it have to be done on each client? What should I set it to?

Thanks again
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Jeremy_Z · l33t Joined: 05 Apr 2004 Posts: 671 Location: Shanghai

This could be done on the switch, reduce the MTU on your vlans devices (ethX.Y) to 1496 (1500-4).
I did not test it but AFAIK it should work as long you do not block ICMP messages on the switch which would prevent MTU dsicovery.
_________________
"Because two groups of consumers drive the absolute high end of home computing: the gamers and the porn surfers." /.
My gentoo projects, Kelogviewer and a QT4 gui for etc-proposals

redbeardmcg · Posted: Sun Dec 03, 2006 8:00 pm Post subject:

My Cisco switch can only increase the MTU (lowest is 1500) so I did it on my workstation (set it to 1496) and it is somewhat better. I can update my portage cache, and do simple things, but it is still really slow.

Should I also change the MTU on the vlan interfaces of my router, or should this be done only on the clients?

Thanks again
_________________
Sacrifice:::Your role may be thankless, but if you're willing to give it your all, you just might bring success to those who outlast you.

Jeremy_Z · l33t Joined: 05 Apr 2004 Posts: 671 Location: Shanghai

Yes you should do it on your router for ethX.Y devices.
_________________
"Because two groups of consumers drive the absolute high end of home computing: the gamers and the porn surfers." /.
My gentoo projects, Kelogviewer and a QT4 gui for etc-proposals

redbeardmcg · Posted: Mon Dec 04, 2006 3:59 am Post subject:

Set MTU to 1496 on both vlan interfaces on my linux router and it works perfect!

Clients can have default MTU now

Thanks again,

Ryan
_________________
Sacrifice:::Your role may be thankless, but if you're willing to give it your all, you just might bring success to those who outlast you.