I'm changing back to Spark (fibre connection on Enable fibre).
What is the appropriate MTU to use for the PPPoE these days, 1492 or 1500?
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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.
My views are my own, and may not necessarily represent those of my employer.
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.
My views are my own, and may not necessarily represent those of my employer.
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
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