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Low bandwith only on one side of a VPN

New Contributor

Low bandwith only on one side of a VPN



I've got a server A behind a SSG5 with a 100Mbit bandwith

I've got a server B behind a SSG140 with a 100Mbit bandwith


There are connected threw a tunnel configure on both router Juniper.

All is working good. Only error that i have sometimes is : 


IPSec tunnel on interface ethernet0/0 with tunnel ID 0x2 received a packet with a bad SPI. IPSERVERA->IPSERVERB, ESP, SPI 0xdbbef600, SEQ 0x1.

My problem is that when i upload a file with scp from B to A i'm at full bandwith but when i do the same from A to B i'm stuck at 100KB/s...
If i try to open several scp connection, then i will have X*100KB/s where X is the number of scp session.

When i do a transfer from B to one of my OVH server (so without VPN) i get my 100Mbit bandwith.

What test can be done to find the problem?


Thank you


New Contributor

Re: Low bandwith only on one side of a VPN

I put MTU from 0 to 1280 on both tunnel interface and it seems that the problem is solve.

Can i have an explanation?