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cpwp
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AirOS v5.5 - PPPoE MTU/MRU

Hi,

It appears that the maximum setting for PPPoE MTU/MRU in AirOS v5.5.x (on an AirRouter version 1119T) is currently 1492.

Our network is configured to allow 1522 byte ethernet frames, so that a 1500 byte PPPoE encapsulated payload can be achieved.

When the mru and mtu options in /etc/ppp/options are set above 1492, pppd seems to ignore them and request 1492, as shown in the pppd debug log:

Jul  4 18:26:51 pppd: Plugin rp-pppoe.so loaded.
Jul 4 18:26:51 pppd: RP-PPPoE plugin version 3.3 compiled against pppd 2.4.4
Jul 4 18:26:51 pppd: pppd 2.4.4 started by admin, uid 0
Jul 4 18:26:51 pppd: PADS: Service-Name: ''
Jul 4 18:26:51 pppd: PPP session is 12
Jul 4 18:26:51 pppd: using channel 9
Jul 4 18:26:51 pppd: Using interface ppp0
Jul 4 18:26:51 pppd: Connect: ppp0 <--> eth1
Jul 4 18:26:51 pppd: sent
Jul 4 18:26:51 pppd: rcvd
Jul 4 18:26:51 pppd: sent
Jul 4 18:26:51 pppd: rcvd
Jul 4 18:26:51 pppd: sent
Jul 4 18:26:51 pppd: rcvd
Jul 4 18:26:52 pppd: rcvd
Jul 4 18:26:52 pppd: sent
Jul 4 18:26:52 pppd: rcvd
Jul 4 18:26:52 pppd: CHAP authentication succeeded: Welcome.
Jul 4 18:26:52 pppd: CHAP authentication succeeded
Jul 4 18:26:52 pppd: peer from calling number 00:15:17:3D:C3:02 authorized
Jul 4 18:26:52 pppd: sent
Jul 4 18:26:52 pppd: rcvd
Jul 4 18:26:52 pppd: sent
Jul 4 18:26:52 pppd: rcvd 01 01 00 0e 01 0a 00 00 00 00 00 00 00 10
Jul 4 18:26:52 pppd: Unsupported protocol 'IPv6 Control Protovol' (0x8057) received
Jul 4 18:26:52 pppd: sent
Jul 4 18:26:52 pppd: rcvd
Jul 4 18:26:52 pppd: sent
Jul 4 18:26:52 pppd: rcvd
Jul 4 18:26:52 pppd: local IP address 80.247.x.x
Jul 4 18:26:52 pppd: remote IP address 80.247.x.x
Jul 4 18:26:52 pppd: primary DNS address 80.247.x.x
Jul 4 18:26:52 pppd: secondary DNS address 80.247.x.x
Jul 4 18:26:52 pppd: Script /etc/ppp/ip-up started (pid 5412)
Jul 4 18:26:52 pppd: Script /etc/ppp/ip-up finished (pid 5412), status = 0x0


/etc/ppp/options looks like this:
debug
plugin rp-pppoe.so
noauth
noipdefault
defaultroute
forcedefaultroute
usepeerdns
lcp-echo-failure 5
lcp-echo-interval 5
lcp-max-configure 10
lcp-max-failure 10
lcp-max-terminate 3
lcp-restart 3
maxfail 0
holdoff 1
persist
nodetach
name "cpwp"
mru 1500
mtu 1500


I have tried increasing the MTU size of the underlying physical interface (eth1 and eth1_real) but this does not have any effect.

Is this configuration possible in AirOS v5.5?

Kind regards,

CP
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cpwp
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Re: AirOS v5.5 - PPPoE MTU/MRU

I should really have done a bit more research before posting.

The version of pppd in AirOS-v5.5 is 2.4.5 - this does not support an MRU/MTU size of >1492 bytes.

The next version of pppd will support this when it has been released.
The code to enable larger MTU/MRU sizes was committed to the pppd git repository in Aug 2010. See:
git.ozlabs.org/?p=ppp.git;a=commit;h=fd1dcdf758418f040da3ed801ab001b5e46854e7

Any chance that the next release of AirOS could include this the pppd from git, please?

CP
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JustJoe
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Re: AirOS v5.5 - PPPoE MTU/MRU

+1 MTU=1500 would indeed be very nice.
Best Regards ... Joe
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PrimoWireless
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Re: AirOS v5.5 - PPPoE MTU/MRU

What happened to this, I see that we still cant have anything larger than 1492 even int he new 5.5.4 firmware?

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UBNT-Matt
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Re: AirOS v5.5 - PPPoE MTU/MRU

v5.5+ supports MTU up to 1600 bytes. Which product are you using? What's the date code (code near MAC address)

 

Thanks,
Matt

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PrimoWireless
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Re: AirOS v5.5 - PPPoE MTU/MRU

Hi Matt,

 

thats correct, I have set our ethernet interfaces to be 1520, and i have also set the MTU/MRU to be 1520/1520 when running in router mode and dialing pppoe, and yet it is still only showing up as 1492.

 

If i run a miktotik in the same configuration is shows that we can easily acheive 1500.

 

This happens on all our CPE, new and old :/

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PrimoWireless
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Re: AirOS v5.5 - PPPoE MTU/MRU

Just to clarify things a bit more:

 

If we run the radio in bridge mode with an MTU of 1520 and then put a mikrotik on the end doing the pppoe and set it as 1500/1500 in the mikrotik, no problems, works 100% and we can see at the server end it gets correct MTU.

 

IF we use the ubnt device in router mode dialing the pppoe on the ubnt device and we set the MTU/MRU to be 1500/1500 or 1520/1520 it still only connects to the pppoe server as 1492 MTU with 1500 MRU.

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PrimoWireless
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Re: AirOS v5.5 - PPPoE MTU/MRU

Oh and the products are:

 

AirGrid M5

NanoBridge M5

NanoStation M5

 

All running off Rocket M5 (which has no issues due to the bridged clients having 1500)

 

Sorry i cant see the date codes by the MAC addresses.

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UBNT-Edmundas
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Re: AirOS v5.5 - PPPoE MTU/MRU

As noticed in first posts, it's PPPoE client issue, that used version doesn't support higher MTU/MRU settings. We will take a look at it in next release.

 

-Edmundas

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WHT
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Re: AirOS v5.5 - PPPoE MTU/MRU

Next release?? The PPPoE / MTU short coming has been around several years.
WHT = Short Form Acronym for "You couldn't handle me even if I came with instructions!"
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UBNT-Edmundas
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Re: AirOS v5.5 - PPPoE MTU/MRU


WHT wrote:
Next release?? The PPPoE / MTU short coming has been around several years.

Do you have any other advises? I'm not sure if we are able to invent time mashine and make these changes in previous airOS releases...

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Wifi442
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Re: AirOS v5.5 - PPPoE MTU/MRU

A vote here as well.  This will be great to have.  I asked about this a while back... Found the post: http://community.ubnt.com/t5/airOS-Software-Configuration/PPPoE-MTU-gt-1492/m-p/219175

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Wifi442
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Re: AirOS v5.5 - PPPoE MTU/MRU

UBNT, Anything new with this? :icon_smile:

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wispr
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Re: AirOS v5.5 - PPPoE MTU/MRU

Checking in on this as well. We're beginning to see more MTU issues related to PPPoE and would like the client to get updated in the next release.

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PrimoWireless
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Re: AirOS v5.5 - PPPoE MTU/MRU

UBNT, can we get an update on this please? with more and more users running tunnels and VPN's, etc we need to be able to offer normal 1500 MTU connections.

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Re: AirOS v5.5 - PPPoE MTU/MRU


PrimoWireless wrote:

UBNT, can we get an update on this please? with more and more users running tunnels and VPN's, etc we need to be able to offer normal 1500 MTU connections.


Increased PPPoE payload to 1500 bytes will be in v5.6 release.

-Edmundas