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Chaosphere64
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OSPF over SSTP - works great but why?

Sun May 30, 2021 2:09 am

Hi everyone,

I have less a problem than a question of understanding. The issue is that I have set up an SSTP tunnel between two MikroTik routers (CHR and RB 4011) and, based on this, OSPF is running in point-to-point mode and advertising networks.

As far as I know, OSPF uses multicast (224.0.0.x) in broadcast and point-to-point mode to send hello packets, set up adjecancies, etc. And furthermore, I assume that PtP VPN tunnels like SSTP do not transmit multicast traffic.

So my simple question would be: why does this work anyway?

Thanks in advance
 
mducharme
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Re: OSPF over SSTP - works great but why?

Sun May 30, 2021 2:47 am

As far as I know, OSPF uses multicast (224.0.0.x) in broadcast and point-to-point mode to send hello packets, set up adjecancies, etc. And furthermore, I assume that PtP VPN tunnels like SSTP do not transmit multicast traffic.
They do transmit multicast. You can do OSPF over any PPP tunnel in point-to-point mode. Most likely the packets to the multicast address are simply "flooded" across the PPP tunnel, and therefore treated much like unicast to the other side.
 
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nichky
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Re: OSPF over SSTP - works great but why?

Sun May 30, 2021 2:59 am

@Chaosphere64

Does SSTP into ospf network? if yes, what you expecting?
 
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Chaosphere64
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Re: OSPF over SSTP - works great but why?

Sun May 30, 2021 2:34 pm

They do transmit multicast. You can do OSPF over any PPP tunnel in point-to-point mode. Most likely the packets to the multicast address are simply "flooded" across the PPP tunnel, and therefore treated much like unicast to the other side.
So then I was probably wrong about that point.

Thanks for clearing things up!

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