Connectionless Network Service (CLNS)

.

R3 Configuration:

!
hostname R3
!
!
!
interface Serial0/0/0
no ip address
encapsulation frame-relay
frame-relay map clns 307 broadcast
no frame-relay inverse-arp
clns enable
clns router isis
no sh
!
!
clns host R3 47.0037.3333.3333.3333.3333.00

router isis
net R3
!
!
!
!

Show clns interface output for R3

Serial0/0/0 is up, line protocol is up
Checksums enabled, MTU 1500, Encapsulation FRAME-RELAY
ERPDUs enabled, min. interval 10 msec.
RDPDUs enabled, min. interval 100 msec., Addr Mask enabled
Congestion Experienced bit set at 4 packets
CLNS fast switching enabled
CLNS SSE switching disabled
DEC compatibility mode OFF for this interface
Next ESH/ISH in 15 seconds
Routing Protocol: IS-IS
Circuit Type: level-1-2
Interface number 0x0, local circuit ID 0x1
Level-1 Metric: 10, Priority: 64, Circuit ID: R3.01
DR ID: 0000.0000.0000.00
Level-1 IPv6 Metric: 10
Number of active level-1 adjacencies: 0
Level-2 Metric: 10, Priority: 64, Circuit ID: R7.01
DR ID: R7.01
Level-2 IPv6 Metric: 10
Number of active level-2 adjacencies: 1
Next IS-IS LAN Level-1 Hello in 6 seconds
Next IS-IS LAN Level-2 Hello in 219 milliseconds

—

R7 Configuration:

hostname R7

interface Serial0/0/0
no ip address
encapsulation frame-relay
frame-relay map clns 307 broadcast
no frame-relay inverse-arp
clns enable
clns router isis
no sh
!
clns host R7 47.0037.7777.7777.7777.7777.00

router isis
net R7
!
!
!

show clns interface output for R7

Serial0/0/0 is up, line protocol is up
Checksums enabled, MTU 1500, Encapsulation FRAME-RELAY
ERPDUs enabled, min. interval 10 msec.
RDPDUs enabled, min. interval 100 msec., Addr Mask enabled
Congestion Experienced bit set at 4 packets
CLNS fast switching enabled
CLNS SSE switching disabled
DEC compatibility mode OFF for this interface
Next ESH/ISH in 25 seconds
Routing Protocol: IS-IS
Circuit Type: level-1-2
Interface number 0x0, local circuit ID 0x1
Level-1 Metric: 10, Priority: 64, Circuit ID: R7.01
DR ID: 0000.0000.0000.00
Level-1 IPv6 Metric: 10
Number of active level-1 adjacencies: 0
Level-2 Metric: 10, Priority: 64, Circuit ID: R7.01
DR ID: R7.01
Level-2 IPv6 Metric: 10
Number of active level-2 adjacencies: 1
Next IS-IS LAN Level-1 Hello in 7 seconds
Next IS-IS LAN Level-2 Hello in 1 seconds

We can see that CLNS was enabled, and with ISIS we are able to pass that route information to the other router, please check the following CLSN Route outputs:

R7#show clns route
Codes: C - connected, S - static, d - DecnetIV
I - ISO-IGRP,  i - IS-IS, e - ES-IS
B - BGP,       b - eBGP-neighbor

C  47.0037.7777 [2/0], Local IS-IS Area
C  47.0037.7777.7777.7777.7777.00 [1/0], Local IS-IS NET

i 47.0037.3333 [110/10]
via R3, Serial0/0/0

if we ping from

R3#ping 47.0037.7777.7777.7777.7777

Type escape sequence to abort.
Sending 5, 100-byte CLNS Echos with timeout 2 seconds
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/34/36 ms
R3#

now if we ping from R7

R7#ping 47.0037.3333.3333.3333.3333

Type escape sequence to abort.
Sending 5, 100-byte CLNS Echos with timeout 2 seconds
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/34/36 ms
R7#

we have reachability, just looking at those CLNP Packets going out from one router to another..

CLNS: Originating packet, size 100
from 47.0037.7777.7777.7777.7777.00
to 47.0037.3333.3333.3333.3333
via 3333.3333.3333 (Serial0/0/0 DLCI 307)
CL    NS: Echo Reply PDU received on Serial0/0/0!
CLNS: Originating packet, size 100
from 47.0037.7777.7777.7777.7777.00
to 47.0037.3333.3333.3333.3333
via 3333.3333.3333 (Serial0/0/0 DLCI 307)
CLNS: Echo Reply PDU received on Serial0/0/0!
CLNS: Originating packet, size 100
from 47.0037.7777.7777.7777.7777.00
to 47.0037.3333.3333.3333.3333
via 3333.3333.3333 (Serial0/0/0 DLCI 307)
CLNS: Echo Reply PDU received on Serial0/0/0!
CLNS: Originating packet, size 100
from 47.0037.7777.7777.7777.7777.00
to 47.0037.3333.3333.3333.3333
via 3333.3333.3333 (Serial0/0/0 DLCI 307)
CLNS: Echo Reply PDU received on Serial0/0/0!
CLNS: Originating packet, size 100
from 47.0037.7777.7777.7777.7777.00
to 47.0037.3333.3333.3333.3333
via 3333.3333.3333 (Serial0/0/0 DLCI 307)
CLNS: Echo Reply PDU received on Serial0/0/0!

Now let see what is installed in the routing table when an interface comes up

R3#deb clns routing
CLNS routing events debugging is on
R3#deb clns pack
CLNS packets debugging is on
R3#conf ter
Enter configuration commands, one per line.  End with CNTL/Z.
R3(config)#int s0/0/0
R3(config-if)#sh
R3(config-if)#
CLNS-RT: Interface Serial0/0/0 was up, now down
CLNS-RT: adjust static routes via   7777.7777.7777 going down
CLNS-RT: adjust static routes via Serial0/0/0   going down
R3(config-if)#
%LINK-5-CHANGED: Interface Serial0/0/0, changed state to administratively down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0/0, changed state to do
wn
R3(config-if)#no sh
R3(config-if)#
CLNS-RT: Interface Serial0/0/0 was down, now up
CLNS-RT: adjust static routes via Serial0/0/0   going up
R3(config-if)#do show
%LINK-3-UPDOWN: Interface Serial0/0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0/0, changed state to up

R3(config-if)#do show clns route

Codes: C - connected, S - static, d - DecnetIV
I - ISO-IGRP,  i - IS-IS,  e - ES-IS
B - BGP,       b - eBGP-neighbor

C  47.0037.3333 [2/0], Local IS-IS Area
C  47.0037.3333.3333.3333.3333.00 [1/0], Local IS-IS NET

i  47.0037.7777 [110/10]
via R7, Serial0/0/0
R3(config-if)#

The IDP + HO DSP (Area) (47.0037.7777) of the NSAP (CLNS Address) is what we see in the Show CLNS Route, and Level 2 Routing logic is performed, to reach each others to send traffic.

R7#show clns protocol

IS-IS Router: <Null Tag>
System Id: 7777.7777.7777.00  IS-Type: level-1-2
Manual area address(es):
47.0037.7777
Routing for area address(es):
47.0037.7777
47.0037.3333
Interfaces supported by IS-IS:
Serial0/0/0 - OSI
Redistribute:
static (on by default)
Distance for L2 CLNS routes: 110
RRR level: none
Generate narrow metrics: level-1-2
Accept narrow metrics:   level-1-2
Generate wide metrics:   none
Accept wide metrics:     none

About the CLSN Addressing, I just wrote the following from several sources and routers output, and I just like to share with you for my/your reference, main Cisco Doc for ISIS used in this text

Another post in relation with this on my blog

R1#conf ter
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#router isis
R1(config-router)# net 47.0011.0000.0001.0100.0100.0101.0101.0101.00

Each IS-IS router must also have a way to uniquely identify itself within the routing domain.

R1(config-router)#net 49.0001.0000.0000.1111.00
%CLNS: System ID (0100.0101.0101.0101) must not change when defining
additional area addresses

This identification is the function of the System ID, which is analogous to the OSPF Router ID

A router can have up to three area addresses

2nd Area Address

R1(config-router)#net 49.0100.0101.0101.0101.00

3er Area address

R1(config-router)#net 50.0100.0101.0101.0101.00

And is could happen if you have more than 3

R1(config-router)#net 51.0100.0101.0101.0101.00
 %The maximum allowed addresses already configured

R1(config-router)#do show run | b ^router isis
router isis
net 47.0011.0000.0001.0100.0100.0101.0101.0101.00
net 49.0001.0102.0304.0506.00
net net 49.0100.0101.0101.0101.00
!

the Network Entity Titles here is defined by rfc163, the use of a .00 of NSel within the NSAP identifies the network layer itself. OSI network layer addressing is implemented with NSAP addresses

R3(config-router)#net ?
XX.XXXX. ... .XXX.XX  Network entity title (NET)

There are 3 NSAP formats:

A simple eight-octet Area ID/System ID format: AREA|SysID|SEL

Area: The Area field is used to route between areas using Level 2 routing.
System ID: The ID field is used to route to a host or router within the area using Level 1 routing.
SEL: The SEL field is used to route to an entity with the host or ES.

A OSI NSAP format: |Area|Area|Area|ID|SEL

and the GOSIP NSAP format

for examples of the different formats check out this Cisco Link

The NET (Network Entity Title) address is the address of the host, where the value in the SEL field is set to 0x00. Refers to the device itself (equivalent to the Layer 3 OSI address of the device)

The NSAP (Network Service Access Point) The SEL field at the end of the ISO address specifies the upper-layer protocol. Similar to the Protocol field of the IP header.

Anyways the routers, informs you about any error:

R3(config-router)#net 00.0000.0000.3333.01
%IS-IS: Invalid NET, N-selector must be zero

and the last note is to remember about having the correct mappings in Non Broadcast Multiaccess Interfaces.
Example:

R3#conf ter
Enter configuration commands, one per line.  End with CNTL/Z.
R3(config)#int Serial0/0/0.322
R3(config-subif)# frame-relay map ip 1.2.23.2 322 broadcas
R3(config-subif)#no frame-relay map clns 322 broadcast
R3(config-subif)#do deb frame-relay pac
Frame Relay packet debugging is on

Serial0/0/0.322:encaps failed on broadcast for link 25(CLNS)

Yes Great Amazing Protocol!