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Joined: Wed Feb 06, 2013 2:48 am

EoIP and MTU

Wed Apr 22, 2015 2:57 am

Hi guys,
I want to create an EoIP tunnel to pass some VLANs through it, I have an Internet connection which is very fast but maximum MTU is 1500 bytes. Using EoIP and then VLAN on it, will it work with such a small MTU size? If yes, do I need to configure anything else or just the EoIP and will it automatically adjust MTUs?

Posts: 484
Joined: Wed Apr 02, 2008 2:12 pm
Location: Minnesota USA

Re: EoIP and MTU

Wed Apr 22, 2015 3:26 am

I've had a lot of bad luck getting "auto-mtu" to function properly and usually results in a mismatch of MTU's between different types of end points i.e. cable modems using DHCP and DSL modems using PPPoE. It ends up, as I indicated earlier, with different mtu's on each end of the link.

Now this can be a EoIP or a GRE tunnel. On top of that, I usually use IPsec to encrypt the links..

I usually have to massage the MTU's on one side or the other, usually the one that is larger to become the same size as the one which is smaller (mtu) to get them to work right using OSPF.

I'll be asking more about this with the "MikroGeniuses" at the MUM tomorrow. 8)
MTCNA - 2011

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