We support a full 1500 byte PPP MTU and that is what I would recommend using.

Many consumer routers do not support it though (i.e. they will max out at 1492).  Sadly the Huawei ones we supply do not.

cbrpilot:

 

We support a full 1500 byte PPP MTU and that is what I would recommend using.

 

Many consumer routers do not support it though (i.e. they will max out at 1492).  Sadly the Huawei ones we supply do not.

 

Thanks @cbrpolit

My EdgeRouter definitely does support it, just wanted to make sure my settings were optimised.

Is VLAN 10 tagging still required as well?

It's interesting that the Huawei doesn't support the the full 1500 MTU. Way back in early 2014 when we got fibre at work we were given the below info from (at the time) Gen-i when we asked about supplying our own router, so they were quite specific about it (emphasis in table NOT added by me). Have things just improved so that 1492 MTU doesn't cause issues anymore, or was it never really that much of a problem?

 

Parameter                 Value                      Description

 

Operating Mode           MDI/MDIX

 

PPP Protocol                PPPoE                    Must support MTU of 1500bytes as per RFC4638.

 

                                                                  If RFC4638 is not supported then the modem must support MSS clamping to avoid any path mtu issues.

 

PPP Username             N/A                          Default PPP Authentication for PPPoE is No Auth

 

PPP Password              N/A                          Default PPP Authentication for PPPoE is No Auth

 

PPP Auth Type             No Auth

 

Encapsulation              802.1Q

 

PCP marking                 0                               For low priority traffic.

 

VID                              10

 

MTU                             AUTO                       Must support MTU of 1500bytes as per RFC4638.

 

                                                                    If RFC4638 is not supported then the modem must support MSS clamping to avoid any path mtu issues.

 

EDIT: It messed up the table I pasted in. Fixed it as best I could.

Yes, VLAN 10 still required.

Huawei support MSS-Clamping, so their support for 1492 works just fine for pretty much all customers.  Where someone could run into MTU issues is anything using UDP for transport as MSS-Clamping is only a TCP thing.  Anything using UDP would have to have some sort of path MTU discovery mechanism etc (and to be honest most of them do). 

My advice to anyone would be to use 1500 if the device supports it. 

cbrpilot:

 

Yes, VLAN 10 still required.

 

Huawei support MSS-Clamping, so their support for 1492 works just fine for pretty much all customers.  Where someone could run into MTU issues is anything using UDP for transport as MSS-Clamping is only a TCP thing.  Anything using UDP would have to have some sort of path MTU discovery mechanism etc (and to be honest most of them do). 

 

My advice to anyone would be to use 1500 if the device supports it. 

 

Thanks for the info @cbrpilot