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Community Member

VPN Site - Site no connect ¿MTU?

Good morning everyone

I'm new to these forums and like you fighting all day with routers and servers.

I've a problem with vpn tunnels with a lot of time and can not be resolved.

The connection is made with the central (877)

AND 3 delegations (827)

Are united through tunnels with ipsec, problems began when they change the public IP address of the plant.

central router ---- --- router ping ok delegations

central router - pinging ok ---- pc delegations

pc ping delegations --- ok - central router

Delegations router --- router ping ok ---- Central

pc central ----- ----- not ping --router pc delegation and delegation.

With the SDM of the plant conducted a test of the tunnel and gave me problems with the MTU should be 1420 to 1512 and this

My question is I've tried changing the MTU from console # ip mtu 1420

And it does not change

How can I change the MTU?

Thanks to all


Re: VPN Site - Site no connect ¿MTU?

You generally do two things:-

1) Change the interface MTU

2) Change the MSS of any TCP transient packets that pass thru the router.

To be honest - it seems hihgly unlikely that chaning the IP of the ISP would require an MTU change.

has anything else changed?

Community Member

Re: VPN Site - Site no connect ¿MTU?

Good afternoon and thank you for reply.

Nothing else has changed.

And when you step directly testing the VPN tunnel, I skip the avisdo that the MTU is not correct. I have to conform to 1420

Anyway I can adjust it from HyperTerminal, you put the command but does not change the MTU.

Any recommendations?

Thank you.

Re: VPN Site - Site no connect ¿MTU?

What version of IOS are you running on the device you want to change the mtu on?

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