(config-if)# isdn switch-type

dingdongboomNetworking and Communications

Oct 27, 2013 (3 years and 7 months ago)

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Integrated services digital network

(ISDN)


Overview:

-
ISDN is a digital dial up circuit switching WAN
technology.

-
Digital end to end so higher speeds & fast setup
than analog.

-
Used as a backup for primary WAN connection
(leased line , F.R).

-
ISDN use 2 types of channels :

1
-

Bearer channel (B
-
chn.).

2
-

Delta channel (D
-
chn.).

-
ISDN services types:

1
-

BRI (basic rate interface).

2
-

PRI (primary rate interface)


ISDN layer model:


B
-
ch D
-
ch

IP, IPX, Appletalk Q.931

PPP, HDLC Q.921

I
-
series

Ex: I
-
430, I
-
431

1
-

Physical layer (L1):

-
I
-
series defines the interfaces of ISDN and
reference points.

-
To implement ISDN connection , the router
must be configured with ISDN switch type
to enable the physical layer
communication.

-
(config)# isdn switch
-
type <type>

2
-

Data link layer (L2):

-
For B
-
ch define any type of circuit
switching WAN encapsulation protocol
(PPP, HDLC).

-
For D
-
ch define LAP
-
D (Q.921)
encapsulation that carry the signaling
information between TE & CO switch.

3
-

Network layer (L3):

-
For B
-
ch define any routed protocol (IP,
IPX, Apple talk).

-
For D
-
ch define control information
protocol (Q.931).


ISDN types:

1
-

ISDN BRI:

-

BRI = 2 * B + 1 * D.

B = 64 kbps, D = 16 kbps.

Basic B.w = 2*64+16 = 144 kbps.

Effective B.w = 2*64 = 128 kbps.

Overall B.w = 144 + 48 = 192 kbps.

48 kbps for framing & synchronization.

2
-

ISDN PRI:

-
T1 (North America) = 23 B + 1 D.

-
E1 (Europe& Egypt) = 30 B + 1 D.

E1

T1

-

D time slot.

15

23

-

Framing.

-

CRC
-
4.

-

E1 multiple
frame = 16 E1

-
SF = 12 frame.

-
ESF = 24 frame.

-

Line
coding.

AMI , HDB3

AMI , B8Z3

ISDN Functions and Reference
Points


Functions are devices or
hardware.


Reference points are
demarcations or interfaces.

Cisco ISDN BRI Interfaces


Configuration :

(config)# isdn switch
-
type <type>

OR (config
-
if)# isdn switch
-
type <type>

(config)# int bri0

(config
-
if)# encapsulation ppp

(config
-
if)# ppp authentication chap

(config
-
if)# isdn spid1 <no.> [<LDN>]

(config
-
if)# isdn spid2 <no.> [<LDN>]

(config
-
if)# ip address <ip> <mask>


DDR (Dial on demand routing):

-
Legacy DDR:

Bound the DDR configuration to the physical
interface , so all dial out calls will have the
parameters.

Configuration:

1
-

Routing protocol (static route)

(config)# ip route <dest. Net.> <mask> <next
hop address>

2
-

Define the interesting traffic.

(config)# dialer
-
list <no.> protocol
<protocol> {permit / deny / list <acl no.>

3
-

Assign dialer list to interface.

(config
-
if)# dialer
-
group <list no.>

4
-

define dialer map.

(config
-
if)# dialer map <protocol> <next hop
address> [name <remote name>] <string>
[speed <rate>]


Optional configuration:

1
-

(config
-
if)# ppp multilink.

(config
-
if)# dialer load
-
threshold <no.> [in /
out / either]

2
-

(config
-
if)# dialer idle
-
timeout <sec.>

-
The time that line can remain idle without
receiving interesting traffic.

3
-

(config
-
if)# dialer fast
-
idle <sec.>

-

Specifies the time that a line for which
there is a contention can remain idle
before the current call is disconnected to
allow competing call to be placed.


Enhanced DDR:


Dialer profile:

-
Separate the logical configuration from the
physical interface.

-
We can configure more than one dialer
configuration for single physical interface.




Troubleshooting:

# show isdn active.

# show int. bri 0.

# show isdn status.

#debug isdn q921.

#debug isdn q931.

Monitoring ISDN BRI