From: Scott Morris (swm@emanon.com)
Date: Tue Apr 05 2005 - 11:16:16 GMT-3
In some countries, your may run DBV/IPE on your cable modem side, but most
places will work in a DOCSIS type environment. As long as the base layer 2
technology has the ability of carrying MAC-oriented frames, then you'll be
able to carry multiple types of things and therefore something like a
secondary L2 encapsulation.
So anything that can forward an Ethernet frame, via compatability or via
bridging can work. At least in theory! The software, of course, will need
to support it.
I'm not sure CDP really makes any difference in this equation.
In the cable modem world, your head-end is going to be a CMTS at Layer 2.
If it's a Cisco CMTS (or many other vendors) it will have L3 capability, but
is not necessarily the terminating point for PPPoE sessions. When designing
a cable network, like any network, you look at putting the appropriate
devices and processing power in the right places. A terminating device
further back in the network is more likely. Whether a 6400 SSG or something
different is a design question. This is why Bruce's example on the DSL-type
design is very similar. Your CMTS or "middle" device will simply bridge
traffic along to where it gets terminated.
In your scenario below, you have the basics covered there.... The MTU
necessary is only 1492. (1500 typical MTU minus the extra 8 bytes for PPP
frame header and FCS).
And in an SP world (your cable modem example) the dialer interface of R will
most likely have "ip address negotiated" in order to receive an IP from the
headend. At the same time, the headend would have some config about "ip
local pool" and "peer default ip address" to assign that information in the
virtual-template.
IMHO if you have PPPoE on the exam you would see it as the client side. So
the configuration you have below (other than MTU) covers the necessary
information. You seem to have the basic thought process down, which is
really the important part! Specific commands and details may change, but as
you understand the flow and thinking, those changes should become a
non-issue in your exam!
HTH,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Jongsoo kim
Sent: Monday, April 04, 2005 4:51 PM
To: ccielab@groupstudy.com
Subject: PPPoE
This is my understanding on this subject after I did some research It seems
to me PPPoE is just a virtual-access link runs over ethernet-frame.
It is more from cable-headend Hub to multiple cable modem. ( cable modem
uses DVB/IPE technology, which works similar as ethernet mac-address) So
cable modem can dial in cable headend hub.
I can use dialer interface or virtual template.
I may have to make sure CDP run over this virtual link.( cdp disabled on VT)
for PPP negotiation.
The only unique requirement is a vdpn.
1) PPPoE over ethernet
Let's say R = remote station and H is cable headend Hub.
So topology is something like
R f0/0--cable modem( whatever) ------ f0/0 H Based on my understanding, I
come up with the following config ( never chance to test)
R would need the following
vpdn enanle
vpdn-group 1( just a name)
request-dialin
protoocl pppoe
interface FastEthernet0/0
pppoe enable
pppoe-client dial-pool-number 10
Interface dialer 1
mtu 1402
ip address 10.1.1.1 255.255.255.0
dialer-group 20
dialer-pool 10
encap ppp
ppp authe chap
ppp chap host R
ppp chap password 0 R-password
dialer-list 20 protocol ip permit
H would need
username R password R-password
vpdn enanle
vpdn-group 1( just a name)
accept-dialin
protoocl pppoe
virtual-template 1
interface FastEthernet0/0
pppoe enable
Interface virtual-template1
mtu 1402
ip address 10.1.1.1 255.255.255.0
ppp authe chap callin
2) PPPoE over ATM
R A1/0--ATM pvc 200/200------ A2/0 H
Based on my understanding, I come up with the following config ( never
chance to test) R would need the following vpdn enanle vpdn-group 1( just
a name) request-dialin protoocl pppoe interface ATM1/0 pvc 200/s00
pppoe-client dial-pool-number 10 Interface dialer 1 mtu 1402 ip address
10.1.1.1 <http://10.1.1.1> 255.255.255.0 <http://255.255.255.0> dialer-group
20 dialer-pool 10 encap ppp ppp authe chap ppp chap host R ppp chap password
0 R-password dialer-list 20 protocol ip permit
H would need
vpdn enanle
vpdn-group 1( just a name)
accept-dialin
protoocl pppoe
virtual-template 1
interface ATM3/0
pvc 200/200
encapsulation aal5autoppp Virtual-Template1 Interface virtual-template1 mtu
1492 ip address 10.1.1.1 <http://10.1.1.1> 255.255.255.0
<http://255.255.255.0> ppp authe chap callin username R6-ppp password 0
NMC-ppp
This archive was generated by hypermail 2.1.4 : Tue May 03 2005 - 07:54:53 GMT-3