Router / ping / PPPoE / packet size question

[kag]

Hi,
I've been having problems since day 1 with my router... the problem is that some people can connect to my ftp and web server, and some other can't.

well I looked at DSLReports.com and Practicallynetworked.com and I think I found out what was causing this, but I'm not sure if I understand the terminology. It seems that this firmware (1.39) does not allow fragmented packets to go through....

anyway I tried to ping me (yeepie.com) with this command line (the connection isn't even supposed to go to the internet because of the "loopback" feature of the router)

ping -l 1600 yeepie.com -- timed out each time
ping -l 1400 yeepie.com -- worked just fine
... and same thing for pinging www.dslreports.com

Now, I read that the max MTU for PPPoE is 1492... I guess this is a PPPoE standard, not an ISP's restriction, right?

Okay, now I'm confused.... I don't know what to think... I believe the ping -l 1600 should be working for yeepie.com (cuz it doesn't go through the internet) ... because maybe because of PPPoE's 1492 limit, it would not work for a site on the 'net... I don't know, this is only a though.

now, when I try to ping *any* of the machines INSIDE my network, with the 192.168.1.x address, it works for -l 1400 AND 1600 ... but when I ping my router (192.168.1.1), it times out for -l 1600 and it works for -l 1400....... so I guess this means that when I ping yeepie.com, it pings my router, right?


I'm not sure if I understand all this, if it seems to be my router that doesn't handle 1492+ packets or it's PPPoE that mixes things up.

It seems that since firmware 1.37 it stopped acting correctly with 1492+ packets, and I can't downgrade my firmware right now.

SOrry for the mixed up post, but any help is appreciated

 

[lowtech1]

When you ping "yeepie.com" it have to go through your router then throught the gateway, then to the back bone. and so one till it reach the machine that youre trying to reach.

It all depend on the firewall/router setup, but it is common to discard fragmented packets because hackers/trojans can enter the network through fragmented packets.

 

[mgpaulus]

Here's what I would guess it going on:

When you ping yipee.com, that is a public IP address provided by your ISP. That address actually belongs to the Modem/router (Depends upon who is being the DHCP client to your ISP). In my case, the 127.x.y.z is actually owned by my Netgear Router. But, it's on the "outside" of your router. So, anyway, any pings to yipee.com have to go to the router for response. You also have the issue of address resolution. yipee.com is probably being resolved to an actual IP by your router's DNS proxy as well.

HTH....

 

[kag]

no no

my router has "loopback" function which means any request to my Internet IP (yeepie.com is mapped to my internet IP) so the packets sent are re-routed to my network without ever going on the internet.

 

[Moonbender]

1492 is the maximum packet size for PPPoE.

 

[kag]

<< 1492 is the maximum packet size for PPPoE. >>



ok so if I ping with a bigger packet, is it supposed to return the ping?