From: stefan vogt (stefan-uwe_vogt@web.de)
Date: Mon Mar 17 2003 - 17:53:17 GMT-3
Hello Brian,
Many thanks for your answers. But your answer rises a new question for me:
>As for Frame-Relay, IS-IS does not run over hub and spoke,
> therefore DIS election is not really an issue.
Why does IS-IS not run over hub and spoke?
-Stefan
"Brian McGahan" <brian@cyscoexpert.com> schrieb am 17.03.03 20:53:23:
>
> Stefan,
>
> The DIS in IS-IS is like the DR/BDR in OSPF. However, the DIS
> election is preemptive, and there is no backup DIS. There is one DIS
> per broadcast segment per level.
>
> To determine which router is the DIS, 'show clns is-neighbors'.
> On a broadcast segment, the Circuit ID is the system ID of the DIS. In
> addition to this, you can see the Pseudonode LSP in the ISIS database.
> In the following example, there are two routers on a broadcast segment,
> R1 & R6. DIS election is on a per level basis. Since R6 has a level-1
> priority of 60, R1 is elected DIS for level-1 (R1 has default of 64).
> However, since R6 has a level-2 priority of 70, it is elected DIS for
> level-2.
>
> R6#sh run int e0/0
> Building configuration...
>
> Current configuration : 142 bytes
> !
> interface Ethernet0/0
> ip address 16.0.0.6 255.0.0.0
> ip router isis
> half-duplex
> isis priority 60 level-1
> isis priority 70 level-2
> end
>
> R6#sh isis databas
>
> IS-IS Level-1 Link State Database:
> LSPID LSP Seq Num LSP Checksum LSP Holdtime
> ATT/P/OL
> R6.00-00 * 0x00000002 0xCA67 1083 0/0/0
> R1.00-00 0x00000004 0x9670 1054 0/0/0
> R1.01-00 0x00000001 0xF2C9 1077 0/0/0
> IS-IS Level-2 Link State Database:
> LSPID LSP Seq Num LSP Checksum LSP Holdtime
> ATT/P/OL
> R6.00-00 * 0x00000001 0xF075 1078 0/0/0
> R6.01-00 * 0x00000001 0x4F29 1079 0/0/0
> R1.00-00 0x00000006 0xB681 1081 0/0/0
> R6#
>
> For the level-1 link state database, you can see that R1
> generates is own LSP as well as an LSP for the pseudonode, denoted by
> the R1.01-00 LSPID. For level-2, R6 is the DIS, hence the LSPID of
> R6.00-00 and R6.01-00.
>
> As for Frame-Relay, IS-IS does not run over hub and spoke,
> therefore DIS election is not really an issue.
>
> For more info on DIS election:
>
> http://www.cisco.com/en/US/tech/tk472/tk474/technologies_tech_note09186a
> 0080094b42.shtml
>
>
> HTH
>
> Brian McGahan, CCIE #8593
> Director of Design and Implementation
> brian@cyscoexpert.com
>
> CyscoExpert Corporation
> Internetwork Consulting & Training
> Toll Free: 866.CyscoXP
> Fax: 847.674.2625
>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > stefan vogt
> > Sent: Monday, March 17, 2003 9:20 AM
> > To: ccielab@groupstudy.com
> > Subject: ISIS and designated IS (DIS)
> >
> > Hi group,
> >
> > I have some questions regarding ISIS and designated IS (DIS).
> >
> > 1) I know that I can change the isis priority per interface. Is the
> DIS
> > eleceted per LAN segment or per area?
> > 2) Is a DIS elected/required also for FR point-to-multipoint
> connections?
> > Which implications does this have to hub-and-spoke type
> configurations?
> > 3) What's the easiest way to figure out which router is elected as
> DIS?
> >
> > Any input or link is appreciated.
> >
> > -Stefan
> >
> ________________________________________________________________________
> __
> > __
> > Gvnnen Sie sich eine Abwechslung vom Wintergrau mit den aktuellen
> > Angeboten von Lufthansa http://img.web.de/lh/lhspecial.html
>
>
This archive was generated by hypermail 2.1.4 : Sat Apr 05 2003 - 08:51:41 GMT-3