Gentoo Forums
Gentoo Forums
Gentoo Forums
Quick Search: in
[SOLVED] Unable to automatically set the MTU
View unanswered posts
View posts from last 24 hours

Goto page Previous  1, 2  
Reply to topic    Gentoo Forums Forum Index Networking & Security
View previous topic :: View next topic  
Author Message
UberLord
Retired Dev
Retired Dev


Joined: 18 Sep 2003
Posts: 6737
Location: Blighty

PostPosted: Mon Aug 31, 2015 10:38 am    Post subject: Reply with quote

NeddySeagoon wrote:
krinn,

A router has two sides an upstream side (WAN) and a downstream side (LAN).
If the WAN port is a PPPoE endpoint then 1492 is correct on the WAN.
As you say, the LAN side should be 1500.

Route MTU discovery will use 1492 going to the WAN and 1500 to the LAN.

The router may have both 1492 and 1500 MTUs configured on the WAN/LAN.


Some firewalls block ICMP which stops Route MTU discovery from working.
This is why I clamp TCP MSS to 1452 on my router. Why 1452? Well, this allows head room for extra packet overhead, such as the PPPoA->PPPoE bridge I have in place.
If your router won't do that, you may need to stick another router in front of it which does allow it - or try the dhcpcd-9999 ebuild to get the above change :)
_________________
Use dhcpcd for all your automated network configuration needs
Use dhcpcd-ui (GTK+/Qt) as your System Tray Network tool
Back to top
View user's profile Send private message
gordonb3
Apprentice
Apprentice


Joined: 01 Jul 2015
Posts: 185

PostPosted: Mon Aug 31, 2015 1:23 pm    Post subject: Reply with quote

POSIX_ME_HARDER wrote:
202 can only go up to 100MBit/s, ....

Those different network speeds may in fact be causing your issues. Not all switches and alike do handle that correctly - I've even seen a Cisco switch once dropping overall speed to far below 10Mbit because it couldn't cope with both 100M and Gigabit devices being connected to it.
Back to top
View user's profile Send private message
POSIX_ME_HARDER
n00b
n00b


Joined: 30 Aug 2015
Posts: 22

PostPosted: Mon Aug 31, 2015 1:39 pm    Post subject: Reply with quote

Configuring a second VLAN on the switch (which I kept calling a router, my bad) too waaaay longer than expected (Windows only software + can't configure it if it's between the ONT and the modem + faulty RJ45 cable), but it's done.
And everything seems to work (I tested the pings this time :roll: ).

It's more avoiding the issue than solving it, but I'll take it.

Thank you very much for your help. I'm impressed by how friendly this forum is. :)
Back to top
View user's profile Send private message
Display posts from previous:   
Reply to topic    Gentoo Forums Forum Index Networking & Security All times are GMT
Goto page Previous  1, 2
Page 2 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum