[j-nsp] monitor traffic on gre inerface

Nilesh Khambal nkhambal at juniper.net
Thu Nov 18 10:19:47 EST 2010

That's normal. When RE sends ospf packet over GRE, it constructs the full packet including the GRE header. So it directly put the packet on the physical interface for transmission. Hence you don't see it in  tcpdump output on GRE interface since outgoing interface is set to the physical interface for the packet.

In the incoming direction, PFE hands off the decapsulated packet to the RE kernel with GRE as Incoming interface. Hence you see the packet in tcpdump on GRE interface.

You will see the similar behavior with aggregate interfaces.  


On Nov 18, 2010, at 7:08 AM, "Sergey" <a_s_y at sama.ru> wrote:

> On Thursday 18 November 2010, Sergey wrote:
>>> did you look at the real interface (tunnel source interface) to
>>> see the outgoing OSPF stuff ?
>> source interface is lo0... But yes, I see it on outgoing interface
>> ge-1/3/0.912.
> And I can't see "input" on it... "In" and "Out" on diffirent interfaces...
> -- 
> Regards,
> Sergey
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