From: Andrew Lissitz \(alissitz\) (alissitz@cisco.com)
Date: Sun Oct 23 2005 - 20:01:18 GMT-3
-----Original Message-----
From: Peter Tran [mailto:pntran1@yahoo.com]
Sent: Saturday, October 22, 2005 10:45 AM
To: Andrew Lissitz (alissitz); comserv@groupstudy.com
Subject: Re: FW: CiscoPress CCIE R&S Practice lab3: PPPoA
Here is the link which describes different encapsulation types for ATM:
http://www.cisco.com/en/US/tech/tk39/tk48/technologies_q_and_a_item09186
a008011a901.shtml#qa4
"A. The following are the four different PVC encapsulation types:
aal5ciscoppp-For Cisco's proprietary PPP over ATM, aal5ciscoppp supports
only Cisco routers with ATM or asymmetric digital subscriber line (ADSL)
interfaces.
Use this type of encapsulation when PPP authentication is desired.
aal5mux-AAL5 MUX encapsulation supports only a single protocol (IP or
IPX) per PVC.
aal5nlpid-AAL5 Network Layer Protocol Identification
(NLPID) encapsulation allows ATM interfaces to interoperate with
High-Speed Serial Interfaces (HSSIs) that are using an ATM data service
unit (ADSU) and running ATM-Data Exchange Interface (DXI).
aal5snap-AAL5 Logical Link Control/Subnetwork Access Protocol (LLC/SNAP)
encapsulation supports Inverse ARP and incorporates the LLC/SNAP that
precedes the protocol datagram. This allows the multiple protocols to
transverse the same PVC.
Note: aal5snap is the default encapsulation and the most widely used
because it allows multiple protocols to be carried over one PVC."
--- "Andrew Lissitz (alissitz)" <alissitz@cisco.com>
wrote:
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of Le Anh Duong
> Sent: Saturday, October 22, 2005 8:00 AM
> To: Cisco certification
> Subject: CiscoPress CCIE R&S Practice lab3: PPPoA
>
> Hi group,
>
> I am very confused with the solution of ATM part, lab 3. Pls help.
> Requirement:
> Configure the ATM PVCs as shown in Figure 3-12. Use point-to-point
> subinterfaces and use the new format PVC vpi/vcConfigure the ATM PVCs
> as shown in Figure 3-12. Use point-to-point subinterfaces and use the
> new format PVC vpi/vci when configuring the PVCs. Ensure that the ATM
> subinterfaces contain purely Layer 2 information, configure virtual
> Layer 3 addresses elsewhere for the ATM connectivity, and make this
> connectivity as secure as possible. This configuration does not
> require any form of bridging.
> Figure 3-12: R6 atm1/0-------------ATM
> cloud-------------atm3/0 R5
> VPI/VCI: 0/99 for both R6 and R5
> (No more any other information)
>
> Solution:
> The clues to the question are not configuring Layer
> 3 and making it
> secure.
> The only way of achieving this is using PPP. ATM is capable of running
> PPP but it requires the encapsulation type aal5ciscoppp and the
> reference to a virtual-template interface.
>
> My confusion is
> 1. Why the aal5ciscoppp encapsulation type is "required" ? Why is it
> not LLC or MUX encapsulation ?
> 2. Do we need to map layer 3 (IP address) information to the pvc
> statically like in the solution ( I think not because PPP is
> encapsulated over ATM not
> IP):
> pvc 0/99
> protocol ip a.b.c.d broadcast
>
> Thanks
> Duong
>
>
This archive was generated by hypermail 2.1.4 : Sun Nov 06 2005 - 22:00:52 GMT-3