Broadband Related > Broadband Hardware
BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
johnson:
The often suggested ZyXEL modems on this forum have great performance, but to my knowledge none support RFC 4638 with MTUs over 1492 for PPPoE connections in bridge mode. As far as I understand, all BT based FTTC connections should support it, but working examples to google are thin on the ground.
Other modems I am aware of with BCM63168 chipset:
Billion 8800nl
Netgear D6400
BT HH5B?
Does anyone have experience with one that can support over 1492 MTU when used as a modem in bridge mode?
[Moderator edited as per thread creator's request.]
highpriest:
I'm on the lookout as well :)
I can't get it working on my Zyxel 8324. I'm currently playing around with a TG589vac v2. But for some reason I can't even get the PPP client on the EdgeRouter to establish a session :mad:
Will report back when I know more.
highpriest:
TG589vac v2 is a no go. Managed to get it working as a bridged modem, but it doesn't support RFC4638 (firmware 17.2).
johnson:
Well I finally got around to playing with MTU settings with the VMG1312 and I feel like I must be missing something but it seems to be working.
After setting a 1508 mtu on the wan interface of a router running openwrt (x86 box with seperate lan cards for wan & lan) it negotiated a ppp session with 1500 byte payload:
--- Code: ---daemon.notice pppd[1630]: pppd 2.4.7 started by root, uid 0
daemon.debug pppd[1630]: Send PPPOE Discovery V1T1 PADI session 0x0 length 10
daemon.debug pppd[1630]: dst ff:ff:ff:ff:ff:ff src 00:00:00:00:00:00
daemon.debug pppd[1630]: [service-name] [PPP-max-payload 05 dc]
daemon.debug pppd[1630]: Recv PPPOE Discovery V1T1 PADO session 0x0 length 48
daemon.debug pppd[1630]: dst 00:00:00:00:00:00 src 00:00:00:00:00:00
daemon.debug pppd[1630]: [AC-name some.thing-here] [PPP-max-payload 05 dc] [service-name] [AC-cookie 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00]
daemon.debug pppd[1630]: Send PPPOE Discovery V1T1 PADR session 0x0 length 30
daemon.debug pppd[1630]: dst 00:00:00:00:00:00 src 00:00:00:00:00:00
daemon.debug pppd[1630]: [service-name] [PPP-max-payload 05 dc] [AC-cookie 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00]
daemon.debug pppd[1630]: Recv PPPOE Discovery V1T1 PADS session 0x3e9 length 48
daemon.debug pppd[1630]: dst 00:00:00:00:00:00 src 00:00:00:00:00:00
daemon.debug pppd[1630]: [service-name] [PPP-max-payload 05 dc] [AC-name some.thing-here] [AC-cookie 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00]
daemon.debug pppd[1630]: PADS: Service-Name: ''
daemon.info pppd[1630]: PPP session is 1001
daemon.warn pppd[1630]: Connected to 00:00:00:00:00:00 via interface eth2
--- End code ---
0x05dc = 1500 for the "PPP-max-payload"
ifconfig on the router then shows a 1500 mtu for the pppoe-WAN interface where it showed 1492 before
Pings get fragmented if over 1464 still, but if you telnet into the VMG1312 and change first the ptm0 and them ptm0.1 interface to 1508 using:
--- Code: ---ifconfig ptm0 mtu 1508
ifconfig ptm0.1 mtu 1508
--- End code ---
Then pings with payload of 1472 magically start working:
--- Code: ---ping -M do -s 1472 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 1472(1500) bytes of data.
1480 bytes from 8.8.8.8: icmp_seq=1 ttl=59 time=18.6 ms
1480 bytes from 8.8.8.8: icmp_seq=2 ttl=59 time=19.0 ms
1480 bytes from 8.8.8.8: icmp_seq=3 ttl=59 time=19.5 ms
1480 bytes from 8.8.8.8: icmp_seq=4 ttl=59 time=18.2 ms
1480 bytes from 8.8.8.8: icmp_seq=5 ttl=59 time=18.8 ms
^C
--- 8.8.8.8 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4004ms
rtt min/avg/max/mdev = 18.222/18.863/19.567/0.470 ms
--- End code ---
Seeing as nothing breaks after setting the WAN port of the openwrt router to 1508, having to run 2 cmds on the modem after a reboot to get it working doesnt seem an issue.
Why I'm sceptical as to whether this result is accurate is that using the tester at http://www.letmecheck.it/ I still get a discovered MTU of 1492. Any idea why I can send unfragmented ICMP packets at 1500 but this test fails? I'l add that when I tried the tester there before with a definite 1492 pppoe connection from the router to modem it comes back with 1500 discovered... *scratches head*
Also tried the exact same steps on a billion 8800nl, same result.
Am I missing something? Is the test for fragmentation I'm using wrong? Have also tried:
--- Code: ---ping -f -l 1472 8.8.8.8
--- End code ---
From a windows 7 VM and got no DF set fragmentation message.
j0hn:
Asus RT-AC68U running AsusWRT-Merlin with a Zyxel VMG1312-B10A in bridge mode.
Following the advice above....
Pinging 8.8.8.8 with 1472 bytes of data:
Reply from 8.8.8.8: bytes=1472 time=19ms TTL=58
Letmecheckit isn't working from my laptop though, i get the error...
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