From: Peter van Oene (pvo@usermail.com)
Date: Thu Oct 24 2002 - 10:00:24 GMT-3
E.D,
At 06:18 PM 10/23/2002 -0400, enginedrive2002 wrote:
>Thanks, Adam! I have some related questions:
>
>1. If I configured router using "router isis", how many "net
><network_entity_title>" I can configure?
3
>2. If I configured router using "router isis <area_tag>", how many "net
><network_entity_title>" I can configure under each process?
3
>3. Will the configuration "isis circuit-type" under interface override the
>"is-type" under router configuration mode?
I believe so, but good thing to test and I have no routers! Of note, if
any would like to send me some 2500's, I'll be glad to test things for you :)
>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.
> > >
> > > ______________________________________________________________________
> > Post
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> >
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