Subject: L2TP/UDP/IP model question

From: "Fabio Poggi" <[email-masked]>
Date: Tue, 7 Nov 2000 13:40:24 +0100

L2TP protocol, in RFC 2661, indicates that UDP/IP stack as one of the transport
media for a tunnel.
So we can have L2TP/UDP/IP/PHY.
L2TP is a particular case of Tunnel over IP.

RFC 2667 ("Tunnel over IP MIB") section 4.1.1 states:
"Each logical interface (physical or virtual) has an ifEntry in the
 Interfaces MIB.  Tunnels are handled by creating a logical
 interface (ifEntry) for each tunnel. These are then correlated, using
 the ifStack table of the Interfaces MIB, to those interfaces on which
 the local IPv4 addresses of the tunnels are configured."

But ifStack model states that only physical interfaces under routing protocol
have to be present in these tables.

So how can I interpret the above RFC 2667 statement ?
Does we have to model l2tpifindex and ifindex of the physical interface under
UDP with a single entry into the ifstack table ?

Thanks.
Regards

---

From: Evan Caves <[email-masked]>
Date: Thu, 09 Nov 2000 14:50:45 -0800

> So we can have L2TP/UDP/IP/PHY.

Not exactly sure what you mean by PHY here, if you mean an L2 protocol
then
yes you can have that.

> have to be present in these tables.

Huh? Can you refresh my memory and point me to the statement in the
ifStack 
MIB that says this.

> So how can I interpret the above RFC 2667 statement ?

An IP tunnel endpoint has an associated IP address, usually one of the
devices
network interfaces (or perhaps a internal loopback interface), that
network
interface is logically bound to an interface in the ifStack model
(perhaps
a PPP, Ethernet or Frame Relay interface). Given this your tunnel
interface 
would then sit on top (in the ifStack) of whatever interface (PPP,
Ethernet 
etc) that the network interface is associated with.

Make (absolutely no) sense,

evan
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