My Lines, My Lines!

In the last section we left off with Frame Relay. In this section we will explore even more transport media such as DSL and ISDN, and others.



Acronym of the Moment:



DSLAM: Digital Subscriber Line Access Multiplexer (Concentrates multiple DSL connections together)

ADSL: Asymmetrical Digital Subscriber Line

POTS: Plain Old Telephone Service

SHDSL: Symmetric High speed Digital Subscriber Line

PPPoE: Point to Point Over Ethernet



DSL is one of the most popular connection media for consumers and companies alike. DSL runs over existing POTS wiring with the use of a DSL modem. This connection feeds into a telephone company's DSLAM. Some J-Series routers have support for ADSL using PPPoE over ATM applications. The interfaces will appear to be ATM connections, but do not support native ATM, only ATM over DSL. Let's take a look at the following example:
[edit]
labuser@labrouter#show interfaces
at-6/0/0 {
encapsulation ethernet-over-atm;
atm-options {
vpi 0;
}
dsl-options {
operating-mode auto;
}
unit 0; {
encapsulation ppp-over-ether-over atm-llc;
vci 0.39;
}
}
Our J-Series Lab router has an ADSL Annex A PIM installed on slot 6. (Annex A is DSL over POTS, Annex B is DSL over ISDN respectively.) The lab router will be a client to our phone company's DSL multiplexer so that the Lab router can act as a DSL modem. As shown in the example above, we are using PPPoe over ATM for our DSL. We need configuration for the physical interface at-6/0/0. and a logical interface. You will notice in our configuration that there is a vci and vpi statement.
VPI is Virtual Path Identifier and VCI is a Virtual Channel Identifier and these must be the same as what is configured at the DSLAM. The remainder of the parameters can be learned from the DSLAM with the operating mode auto statement.

"On to Our Logical Interface...."

Now that we have our ATM interface, we now will configure an internal PPPoE interface and its' mappings. We need to map our physical interface where PPPoE will be running, the access server, and underlying requested services. See Below:

pp0{
unit 0{
pppoe-options{
underlying-interface at-6/0/0.0;
access-concentrator labisp;
service-name pppserv@labisp;
auto-reconnect 5;
}
family inet{
negotiate-address
}
}
}
}
You can verify your new connection with run show pppoe interfaces.

ISDN is a protocol designed to run over the public telephone network. Like Frame Relay, ISDN is seeing less deployment with the emergence of DSL and other broadband technologies. Just like in our previous example, ISDN on a Juniper router requires a logical interface and a physical one. Our physical interface, br which will contain the dialing number and switch type. In our lab router br-0/0/4 will be configured with a switch type of etsi for Europe NET3. Also, a dial pool we create will map our physical interface to a logical unit in our dialer interface. First we configure our physical interface:

[edit interfaces]
br-0/0/4{
isdn-options{
switch-type etsi;
}
dialer-options{
pool labpool1;
}
}
Now on to the dialer interface which contains our number we need a number to dial, an IP address, and our pool mapping our logical interface to br-0/0/4... dl0 will be our dialer interface and we will set up our "dialer filter" to establish a connection only when there is "interesting traffic" (More on this in a moment.)

dl0{
unit 0{
dialer-options{
pool labpool1;
dial-string 5559999;
}
family inet{
filter{
dialer dial_filter;
}
address 12.12.20.1/24;
}
}
}

Here is our simple dialer filter "dial_filter" that brings up our connection any time packets are destined for 12.12.20.2 using the note action. All other destinations are ignored in term b without a corresponding from statement.

[edit]
firewall{
family inet{
dialer-filter dial_filter{
term a{
from{
destination-address{
12.12.20.1/24
}
}
then note;
}
term b{
then ignore;
}
}
}
}

ISDN is commonly used as a backup link for other interfaces if they fail. To configure the ISDN as backup, the dl0 interface can be mapped to our interface requiring backup. The interface we are backing up is fe-0/0/1:

[edit interfaces fe-0/0/1 unit 0]
backup-options{
interface dl0.0;
}
Presumably, the ISDN interface would stay up even if the entire path is not reachable. It is also wise to configure a list of reachable IP networks when interfaces are working normally. In our lab example, a single network of 13.13.20.0/24 is used to verify connectivity with the use of a watch list.

dl0{
unit 0{
dialer-options{
pool labpool1;
dial-string 5559999;
watch-list{
13.13.20.0/24;
}
}
family inet{
address 13.13.20.1/24;
}
}
}
You can make calls between ISDN devices. To accept a call, an incoming dialer map can be configured on dl0:
dl0{
unit 0{
dialer-options{
pool labpool1;
incoming-map;
watch-list{
caller 384030;
}
}
family inet{
address 12.12.20.1/24;
}
}
}
You can use the show isdn and show dialer commands to verify the interface is working. show isdn will verify Layers 1-3 connectivity and switch type. show dialer will indicate per channel status.