PPPoe and MTU's and iBurst

R

Ravilj

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Ok apparently the iBurst servers have their MTU's set to a default 1352.

Now what is the standard MTU for a pppoe connection?

When I connect with rp-pppoe my MTU is either 1432 or 1452...
ppp0 Link encap:Point-to-Point Protocol
inet addr:196.2.115.208 P-t-P:196.30.31.100 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1452 Metric:1
RX packets:3536 errors:0 dropped:0 overruns:0 frame:0
TX packets:3533 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:1831954 (1.7 Mb) TX bytes:643328 (628.2 Kb)

o_O / # \
Click to expand...

So why does rp-pppoe detect it differently? Why does it not set it to 1352?

I have been reading through this:
http://www.e-infomax.com/ipmasq/howto/c-html/mtu-issues.html
Now what is PMTU?

Could someone give me an explanation for this, why do I have to go into so much trouble with setting up the MTU on my side? Do the ADSL users have issues with this?
 
PPPOE apparently adds an additional 8 bytes to your packets. I cannot explain your queries, but I've used the following:

My IPCop sets the MTU to either 1492 (with occasional problems) or 1432, so I set it to 1432 on IPCop and 1424 on my other pc's to be safe. This seems to work fine.

I had one instance on dial-up where I had to lower it to 1352 for a reliable connection using Win XP ICS from a non-dialup machine (using Surecom net card).
 
Last edited:
When I connect to the internet through iBurst on my 2 machines simutaneously both slow down a fair amount. I have made no changes to any MTU settings or the like and am using Windows XP ICS. Will changing these settings make a difference at all?
 
I'd suggest that you use a router or an IPCop / Smoothwall machine (as router and firewall) to connect to iBurst if you want to use multiple pc's. Once the router connects properly you're unlikely to have to change anything on the other pc's.

Apart from that, ICS can be rather resource intensive. I found that on Windoze XP and Fedora Core 2/3.
 
why do I have to go into so much trouble with setting up the MTU on my side? Do the ADSL users have issues with this?
 
Just set it to 1352. There is no performance difference in the 1300-1400 range.
 
I have now, lets hope rp-pppoe defaults the MTU to 1352. *sigh* iBurst gives me grey hair and I havent even reached a quarter of a century "/
 
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