From: Adam Crisp (adam.crisp@totalise.co.uk)
Date: Thu Oct 24 2002 - 04:12:26 GMT-3
1. 3, this is because of the number of bytes available in the address header
of the lsa
2. 3 , router isis = router isis <null>, same as specifying a tag
3. isis circuit type specifies what sort of LSA to send (L1, L2).
If you have a is-type level-1 under the isis process, then obviously you
cant send L2 LSA's
If you have a is-type level-2 under the isis process, then obviously you
cant send L1 LSA's
Adam
-----Original Message-----
From: enginedrive2002 [mailto:enginedrive2002@yahoo.ca]
Sent: 23 October 2002 20:19
To: ccielab@groupstudy.com; Adam Crisp
Subject: Re: IS-IS area and process.
Thanks, Adam! I have some related questions:
1. If I configured router using "router isis", how many "net
<network_entity_title>" I can configure?
2. If I configured router using "router isis <area_tag>", how many "net
<network_entity_title>" I can configure under each process?
3. Will the configuration "isis circuit-type" under interface override the
"is-type" under router configuration mode?
Thank you very much!
E.D.
----- Original Message -----
From: "Adam Crisp" <adam.crisp@totalise.co.uk>
To: "enginedrive2002" <enginedrive2002@yahoo.ca>; <ccielab@groupstudy.com>
Sent: October 23, 2002 12:51 PM
Subject: RE: IS-IS area and process.
> NO,
> the rule of a router being completely within an area is true of ISIS -
OSI,
> or TCP/IP is irrelevent.
> I am sorry to confuse you with Multi ISIS processes, but I was trying to
> explain why Cisco call the ISIS process the Area_tag.
>
> The ISIS area changes on the wire, not withing the router.
> You can run Multi-ISIS processes, but an interface can only exist within
ONE
> isis process.
>
>
> The sentence " a router is completely within an area" could be written:
> "A router is completly within an area and you enable which interfaces run
> the ISIS protocol."
>
> hope I haven't confused you.
>
> You just need to remember:
>
> 1. Address the router, not the interfacs
> 2. LSA's are generated for each interface that is enabled for ISIS
routing.
> 3. There are two sorts of adjecency:
> 3a. L1 is used between routers in the same Area
> 3b. L2 is used between routers in different Areas ( where area is not the
> systems id - see way below!) and optionally between Routers in the local
> Area.
> 4. L2 IP routes carry all IP information
> 5. L1 IP routes only carry IP information about the local ISIS area
> 6. If a router with a L2 database is a neigbour with a L1_ONLY router,
then
> it will inject a default router to the local ISIS topology
>
> Enjoy ;-)
>
> Adam
>
>
>
> -----Original Message-----
> From: enginedrive2002 [mailto:enginedrive2002@yahoo.ca]
> Sent: 23 October 2002 17:30
> To: Adam Crisp; ccielab@groupstudy.com
> Subject: Re: IS-IS area and process.
>
>
> Thank you very much, Adam!
>
> It's getting clearer and clearer now. Based on your explanation, can I say
> "the rule of a router is completely within an area is true for TCP/IP,
but
> false for CLNS"?
>
> I have so little knowledge about CLNS, hope this conclusion doesn't sound
> funny to you guys. :-)
>
>
> E.D.
>
> ----- Original Message -----
> From: "Adam Crisp" <adam.crisp@totalise.co.uk>
> To: "enginedrive2002" <enginedrive2002@yahoo.ca>; <ccielab@groupstudy.com>
> Sent: October 23, 2002 12:02 PM
> Subject: RE: IS-IS area and process.
>
>
> >
> >
> > yes, I see your problem.
> >
> > the Area Tag is definitely a Process ID.
> > this is because if you were to have a router with more than one ISIS
> routing
> > process, then you would support more that one NSAP Area.
> > eg
> > !
> > router isis 1
> > net 49.0001.1111.1111.1111.00
> > !
> > router isis 2
> > net 49.0002.1111.1111.1111.00
> > is-type level-1
> > !
> > Router2#show clns
> > Global CLNS Information:
> > 0 Interfaces Enabled for CLNS
> > NET: 49.0001.1111.1111.1111.00
> > NET: 49.0002.1111.1111.1111.00
> > Configuration Timer: 60, Default Holding Timer: 300, Packet Lifetime
64
> > ERPDU's requested on locally generated packets
> > Intermediate system operation enabled (CLNS forwarding allowed)
> > IS-IS level-1-2 Router: 1
> > Routing for Area: 49.0001
> > IS-IS level-1 Router: 2
> > Routing for Area: 49.0002
> > Router2#
> >
> >
> >
> >
> > This is all about OSI and network management
> > ISIS can router OSI traffic - ie OSI clns
> >
> > OSI CLNS/CLNP is used in optical network management land, where devices
> like
> > Optical Add and Drop Multiplexors need to me managed, and the network
> > protocol used is OSI - NOT TCP/IP!!
> >
> > The ADM's route OSI traffic between them using ISIS - and you can
imaging
> > that physically the devices can be hundreds of miles apart if they're
> > connected via optical fibres.
> >
> > There is a limit to the number of Network Elements in any one Area,
(ISIS
> L1
> > area) -
> > The ADM network would therefore be split up into a number of L1 Areas.
> >
> > At some point the OSI traffic need to get back to a Network management
> > center - and there is a gateway to a regular Cisco Router.
> > Instead of having one router for every OSI Area (connected together via
L2
> > links), a Cisco router can support more that one Area (upto 26)
> >
> > More than one Area -------- More that one ISIS process
> >
> > hense the "router isis <area_tag>" ==== "router isis <process Id>
> >
> > In the scenario I've just tried to outline, the Cisco router would have
a
> L2
> > link to the Telco's core network.
> > Only one ISIS process can support L2 LSP's
> >
> > Hope this helps
> >
> > Adam
> >
> >
> > -----Original Message-----
> > From: enginedrive2002 [mailto:enginedrive2002@yahoo.ca]
> > Sent: 23 October 2002 16:36
> > To: Adam Crisp; ccielab@groupstudy.com
> > Subject: Re: IS-IS area and process.
> >
> >
> > Adam,
> >
> >
> > Thanks for your information.
> >
> > Regarding command "router isis <a_number_here>", my understanding is
like
> > yours, it's a process number. But if you check the IOS command
reference,
> > the syntax is "router isis <area_tag>".
> >
> > This comes with my confusion. The first thing I learn about IS-IS is "a
> > router is completely within an area, and the area borders are on links,
> not
> > on routers". If we could configure several "router isis <area_tag>" on a
> > single router, didn't it bread the rule above, which make the area
border
> on
> > the routers? If we both accept the rule is true, would this make process
> > equal to area? Or the rule above is wrong in the very beginning?
> >
> > Thanks!
> >
> >
> > E.D.
> >
> > ----- Original Message -----
> > From: "Adam Crisp" <adam.crisp@totalise.co.uk>
> > To: "enginedrive2002" <enginedrive2002@yahoo.ca>;
<ccielab@groupstudy.com>
> > Sent: October 23, 2002 11:00 AM
> > Subject: RE: IS-IS area and process.
> >
> >
> > > should read at bottom of previous post:
> > > R1: NSAP net 39.826f.3142.0000.0000.0002.0006.0010.7b38.0001.00
> > > R2: NSAP net 39.826f.3142.0000.0000.0002.0007.0010.7b38.0002.00
> > > R3: NSAP#1: net 39.826f.3142.0000.0000.0002.0006.0010.7b38.00de.00
> > > R3: NSAP#2: net 39.826f.3142.0000.0000.0002.0007.0010.7b38.00de.00
> > > R3: NSAP#3: net 49.0001.0006.0010.7b38.00de.00
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > > Adam Crisp
> > > Sent: 23 October 2002 15:44
> > > To: enginedrive2002; ccielab@groupstudy.com
> > > Subject: RE: IS-IS area and process.
> > >
> > >
> > > Hi,
> > >
> > > It is possible to run more than one ISIS routing process on a router.
> > > This is a bit like running more that one OSPF process.
> > > Actually, you can run more that one ISIS process, but only one process
> can
> > > generate and maintain a Level-2 database.
> > > example:
> > >
> > > router isis 10
> > > !This runs as isis process with a process ID of 10
> > > !This is NOT an automonous system number - it's a process ID - and
never
> > > leaves the router
> > > !this is is bit like typing 'router ospf 10'
> > >
> > > router isis 20
> > > !This runs as isis process with a process ID of 10
> > >
> > > router isis
> > > !This runs as isis process with a process ID of NULL - note that you
> > can't
> > > do this with OSPF
> > >
> > >
> > > The net statement under isis is a long number that is known as an NSAP
> > > address. This is a but like an X.500 address.
> > > this is described at
> > >
> >
>
http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuratio
> > > n_guide_chapter09186a008007fd45.html#1012605
> > >
> > > A very basic description of an NSAP address is:
> > >
> > > 1. AFI - Format Identifier - How long is the address, where are the
byte
> > > boundaries atc.
> > > 2. IDI DFI AAI - Organisation - an attempt at describing the
> > organisation
> > > that holds the address
> > > 3. Domain - a number, a bit like autonomous system
> > > 4. Area - a number, a bit like an OSPF area ID
> > > 5. End system ID, a unique ID, can be anything but must be unique,
> > Ethernet
> > > MAC addresses are frequently used as these are already unique.
> > > 6. N-selector - a bit like TCP port number
> > >
> > > Different AFI's define different lengths, and different content of the
> > NSAP
> > > address. - ie picked from the list above
> > >
> > > eg AFI 49 - example 49.0001.0006.0010.7b38.00de.00
> > > AFI 49 - 49.aaaa.iiii.iiii.iiii.iiii.nn
> > > where a=area, i=systemID, n=N-sel
> > >
> > > eg AFI 39 - example net
> > 39.826f.3142.0000.0000.0002.0006.0010.7b38.00de.00
> > > 39 net 39.idi .dfi .afi .dddd.aaaa.iiii.iiii.iiii.nn
> > >
> > > Does this answer your question?
> > >
> > > In practice, we are only intesested in two parts of the NSAP address,
> > > 1. Area
> > > 2. System ID
> > >
> > > more...
> > > Routing protocols - ISIS only exits on two levels
> > > Level-1 - can route between System ID's
> > > Level-2 - can route between Areas
> > >
> > > Level-3 - routing between domains.. well this doesn't exist, Cisco or
> > > somebody once thought up IDRP - Interdomain Routing Protocol - but
this
> > was
> > > never implemented. - at least I've never seen it in an IOS release. My
> > guess
> > > is that the MBgp development will sort this out.
> > >
> > > As ISIS is only L1,L2 aware, we are only interested in AREA and
> SYSTEM_ID
> > > The area is all the NSAP address that is NOT the system ID. Therefore
> > >
> > >
> > > ISIS sees the NSAP as two parts, Area and System ID:
> > > NSAP: 39.826f.3142.0000.0000.0002.0006.0010.7b38.00de.00 will be
treated
> > as:
> > > NSAP: 39.aaaa.aaaa.aaaa.aaaa.aaaa.iiii.iiii.iiii.00
> > >
> > > Back to level-1 again,
> > > In order for ISIS adjecencies to form, the area must be the same.
> > >
> > > It is possible for three different NSAPS to be configured on the same
> > > routing process
> > > eg.
> > > !
> > > router isis
> > > net 39.826f.3142.0000.0000.0002.0006.0010.7b38.00de.00
> > > net 39.826f.3142.0000.0000.0002.0007.0010.7b38.00de.00
> > > net 49.0001.0006.0010.7b38.00de.00
> > > !
> > >
> > > this has the effect of MERGING the areas together, therefore you could
> > have:
> > > R1---R2----R3, connected together with serial interfaces
> > > the following NSAP addresses configured:
> > > R1: NSAP net 39.826f.3142.0000.0000.0002.0006.0010.7b38.0001.00
> > > R2: NSAP net 39.826f.3142.0000.0000.0002.0006.0010.7b38.0002.00
> > > R3: NSAP#1: net 39.826f.3142.0000.0000.0002.0006.0010.7b38.00de.00
> > > R3: NSAP#2: net 39.826f.3142.0000.0000.0002.0007.0010.7b38.00de.00
> > > R3: NSAP#3: net 49.0001.0006.0010.7b38.00de.00
> > >
> > > Since r3 above merges the "areas" R1 and R2 WILL form an adjecency.
> > >
> > >
> > > Good luck
> > >
> > > Adam
> > >
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > > enginedrive2002
> > > Sent: 23 October 2002 14:41
> > > To: ccielab@groupstudy.com
> > > Subject: IS-IS area and process.
> > >
> > >
> > > Hi, Group
> > >
> > >
> > > The concept of area and process in IS-IS really bothering me,
sometimes
> > they
> > > look like the same, sometimes they are not. Could someone explain them
> to
> > > me?
> > >
> > > Thank you!
> > >
> > >
> > > E.D.
> >
> > ______________________________________________________________________
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>
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