Connectionless Network Service (CLNS)
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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
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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!
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