5- GRE Tunnel MTU & MSS

[@marianah8127]

Thank you for the explanation! I'd also like to know about the mtu and mss when ipsec is used.

[@abdulkhokhar2004]

Best explanation! Thank you!

[@jamesholley]

Thanks for that, nicely explained.

[@alriyada2008]

You are the best

[@fraser5643]

Layer 2 MTU is 1518 Layer 3 is 1500

[@aaronjg77]

Thank you! I’m glad somebody else noticed. I was screaming at my IPad screen when he said that.

[@tarikkachkach9g562]

شكرا 😊

[@acastano59]

Great! Thanks :o)

[@givememore9407]

good explanation... So you mean to say we need to configure MTU "1436" on the tunnel? Please explain where else we need to configure the same MTU"1436"

[@RK-ly5qj]

Hm. I had a problem with OpenVPN performance. Once some has notice that i need to try sth with mss mtu. So i guess it must be it. But where im looking to my WAN connection interface on Sophos XG i can see that default its 1500mtu. So from you film i can think that i must do 1500-20-4 = 1476 Next for OpenVPN settings i need to 1486 --20-20=1436. Am I right ? Did i understood your explanation corretly ? I:ll be glad to hear your answer. Thx in advance ^^

[@vpcnetwork3181]

Correct .

[@BeniSAV]

Спасибо, я понял как вычислять MTU. Получается, что для хорошей работы этой сети которая представлена на схеме нам нужно на этих трёх устройствах задать MTU 1436 ? ip mtu 1436

[@samip537]

But what about dual-stack GRE tunnel? Aka encapsulating both IPv4 and IPv6 traffic?

[@tanmoymallick8244]

1476 is the MSS value not MTU.. Frm minute 3 you are saying it is MTU. Note, we generally adjust the mss value so that we can give the room for other headers like gre ipsec apart from 20 bytes of IP header and 20 bytes of tcp header

[@akashvikraman7946]

Assume we have a host and 3 routers connection serially with different mtu. How does the tcp sender and receiver calculates mss value

[@vpcnetwork3181]

If I understand your question very well . The TCP MSS will be the lowest one in the path .

[@KalalayamFestivalmedia]

I have 2 connections primary broadband and secondary MPLS primary netwok maximum MTU value is 1354 Secondary network maximum value is 4110 Our camera view is not available in headoffice but available in branch Via broadband connection is working perfectly but with mpls it's not working It's ISP issue or our MSS issue Please help me