From: Joseph Saad (joseph.samir.saad@gmail.com)
Date: Sat Nov 10 2007 - 17:17:36 ART
Thank you Shiran. This answers my question.
On Nov 11, 2007 12:15 AM, shiran guez <shiranp3@gmail.com> wrote:
> and here is why you see only on one of the ABR's the N2:
>
> 3.3 Flushing Translated Type-7 LSAs
>
> If an NSSA border router has either translated or aggregated an
> installed Type-7 LSA into a Type-5 LSA that should no longer be
> translated or aggregated, then the Type-5 LSA should either be
> flushed or reoriginated as a translation or aggregation of other
> Type-7 LSAs.
>
>
>
>
> On Nov 10, 2007 10:14 PM, shiran guez <shiranp3@gmail.com> wrote:
>
> >
> > Here is a quate from RFC 3101, this is what i mean by saying that the
> concept is only one exit for stub and NSSA.
> >
> > 3.1 Type-7 Translator Election
> >
> > It is not recommended that multiple NSSA border routers perform
> > Type-7 to Type-5 translation unless it is required to route packets
> > efficiently through Area 0 to an NSSA partitioned by Type-7 address
> > ranges. It is normally sufficient to have only one NSSA border
> > router perform the translation.
> >
> >
> >
> >
> >
> > On Nov 10, 2007 10:10 PM, Joseph Saad <joseph.samir.saad@gmail.com> wrote:
> >
> > > I just disagree with the statement:
> > >
> > >
> > > the concept of NSSA and Stub Areas is one exit only.
> > >
> > > The concept of NSSA is to eliminate type 3, 4 and 5 LSA's while
> > > allowing redistribution via having type 7.
> > > The concept of stub area is to eliminate type 3,4,5 and never allow
> > > redistribution.
> > >
> > > There's no such mandate on the number of ABR (exits) to be one.
> > >
> > > Anyhow, reading RFC 3101 for enlightenment.
> > >
> > > cheers,
> > > Joseph.
> > >
> > >
> > >
> > >
> > > On Nov 11, 2007 12:04 AM, shiran guez <shiranp3@gmail.com> wrote:
> > > > R1 is the ABR for the NSSA so you will see the N2 sent from R6 ASBR as
> you
> > > > see now, and R1 as you can see in the DB did the translation for area
> 0 and
> > > > inside Area 0 on R5 you should see the E2, there is no preferance of
> N2 over
> > > > E2.
> > > >
> > > > N2 is exactly the same as E2 but for routes that came from NSSA.
> > > >
> > > > R1 is the translator meaning that he recive from R6 and you see the
> routes
> > > > recived on the routing table as they are valid and applying to the
> linkstate
> > > > rules. and then R1 is translating and sending out to area 0.
> > > >
> > > > the concept of NSSA and Stub Areas is one exit only.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > On Nov 10, 2007 9:32 PM, Joseph Saad <joseph.samir.saad@gmail.com >
> wrote:
> > > >
> > > > >
> > > > >
> > > > >
> > > > > Here's an elaboration on the issue.
> > > > >
> > > > > R1
> > > > >
> > > > > R6 (A1) (A0) R5.
> > > > >
> > > > > R4
> > > > >
> > > > > R1, R4 and R6 shares the same VLAN and is in area 1.
> > > > > R1, R4 and R5 are on a Hub-n-spoke with R5 as the hub and is in area
> 0
> > > > > R6 is the ASBR (where I am doing redistribution of static subnets).
> > > > >
> > > > > Rack1R6(config-router)#do sh runn | s ip route|router ospf
> > > > > router ospf 1
> > > > > router-id 150.1.6.6
> > > > > log-adjacency-changes
> > > > > area 1 nssa
> > > > > redistribute static subnets
> > > > > network 150.1.6.6 0.0.0.0 area 1
> > > > > network 155.1.146.6 0.0.0.0 area 1
> > > > >
> > > > > ip route 160.1.6.0 255.255.255.0 Null0
> > > > >
> > > > >
> > > > > The first ABR
> > > > >
> > > > > Rack1R1#sh runn | s router ospf 1|ip route
> > > > >
> > > > > router ospf 1
> > > > > router-id 150.1.100.100
> > > > > log-adjacency-changes
> > > > > area 1 nssa
> > > > > network 150.1.1.1 0.0.0.0 area 1
> > > > > network 155.1.0.1 0.0.0.0 area 0
> > > > > network 155.1.146.1 0.0.0.0 area 1
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > Rack1R1#sh ip route ospf
> > > > > 160.1.0.0/24 is subnetted, 1 subnets
> > > > > O N2 160.1.6.0 [110/20] via 155.1.146.6, 01:04:19,
> FastEthernet0/0
> > > > > 150.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
> > > > > O 150.1.6.6/32 [110/2] via 155.1.146.6, 01:04:19,
> FastEthernet0/0
> > > > > O 150.1.5.5/32 [110/65] via 155.1.0.5, 01:05:14, Serial1/0
> > > > > O 150.1.4.4/32 [110/2] via 155.1.146.4, 01:04:19,
> FastEthernet0/0
> > > > >
> > > > >
> > > > > >> "Note that the route to 160.1.6.0 shows as N2"
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > Rack1R1#sh ip ospf database | b Type-7
> > > > > Type-7 AS External Link States (Area 1)
> > > > >
> > > > > Link ID ADV Router Age Seq# Checksum Tag
> > > > > 160.1.6.0 150.1.6.6 11 0x80000004 0x005C48 0
> > > > >
> > > > > Type-5 AS External Link States
> > > > >
> > > > > Link ID ADV Router Age Seq# Checksum Tag
> > > > > 160.1.6.0 150.1.100.100 2037 0x80000002 0x002AC9 0
> > > > >
> > > > >
> > > > > >> This shows that Router 1 is doing the translation and is
> > > > > originating the Type-5 LSA in the OSPF domain (except Stub and NSSA
> > > > > areas).
> > > > >
> > > > >
> > > > >
> > > > > On the other ABR (R4)
> > > > >
> > > > > Rack1R4#sh ip route ospf
> > > > > 160.1.0.0/24 is subnetted, 1 subnets
> > > > > O E2 160.1.6.0 [110/20] via 155.1.146.6, 01:09:32, Ethernet0/1
> > > > > 150.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
> > > > > O 150.1.6.6/32 [110/11] via 155.1.146.6, 01:09:39, Ethernet0/1
> > > > > O 150.1.5.5/32 [110/65] via 155.1.0.5, 01:10:23, Serial1/0
> > > > > O 150.1.1.1/32 [110/11] via 155.1.146.1, 01:09:39, Ethernet0/1
> > > > >
> > > > >
> > > > >
> > > > > >> "Note that the route to 160.1.6.0 shows as E2"
> > > > >
> > > > >
> > > > > Rack1R4#sh ip ospf data | b Type-7
> > > > > Type-7 AS External Link States (Area 1)
> > > > >
> > > > > Link ID ADV Router Age Seq# Checksum Tag
> > > > > 160.1.6.0 150.1.6.6 197 0x80000004 0x005C48 0
> > > > >
> > > > > Type-5 AS External Link States
> > > > >
> > > > > Link ID ADV Router Age Seq# Checksum Tag
> > > > > 160.1.6.0 150.1.100.100 180 0x80000003 0x0028CA 0
> > > > >
> > > > >
> > > > >
> > > > > My questions are:
> > > > >
> > > > > 1) Why R1 is showing the route as N2 for 160.1.6.0?
> > > > > 2)isn't Type-5 preferred over Type-7?
> > > > >
> > > > >
> > > > > I would have expeceted to see R1 to have this route as E2 (i.e.
> similar to
> > > > R4).
> > > > >
> > > > > Thanks,
> > > > > Joseph.
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > On Nov 10, 2007 11:15 PM, Joseph Saad <joseph.samir.saad@gmail.com>
> wrote:
> > > > > > Hi Shiran,
> > > > > >
> > > > > > I am referring to IE technology Lab "NSSA Area type 7to5 LSA
> > > > > > Translator Election".
> > > > > >
> > > > > > Regarding your Answer:
> > > > > >
> > > > > > When you use a NSSA not so stubby area then the ASBR will generate
> N2
> > > > > > for external into the area.
> > > > > >
> > > > > > >> "I am OK with that"
> > > > > >
> > > > > > E2 is for external routes and will be generated by ASBR.
> > > > > >
> > > > > > >> "I am OK with that for Normal Areas".
> > > > > >
> > > > > > in a router that have under his process an Area type NSSA will
> convert
> > > > > > the Type 7 LSA to Type 5 when going from NSSA to the Backbone
> Area.
> > > > > >
> > > > > > >> "True, but what if we have multiple ABR such as this particular
> > > > > > technology lab".
> > > > > >
> > > > > > there are no election for ABR or ASBR, if your router have under
> his
> > > > > > process more then one area then he is ABR, if he have
> redistribution
> > > > > > (or originating a default route) then he is ASBR.
> > > > > >
> > > > > > >> "True, but if you have multiple ABR's for the NSSA, one of them
> > > > > > (i.e. with the highest router-id) is elected for translating the
> type
> > > > > > 7 into type 5 LSA".
> > > > > >
> > > > > > Joseph.
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > On Nov 10, 2007 11:00 PM, shiran guez < shiranp3@gmail.com> wrote:
> > > > > > > when you use a NSSA not so stubby area then the ASBR will
> generate N2
> > > > for
> > > > > > > external into the area.
> > > > > > >
> > > > > > > E2 is for external routes and will be generated by ASBR.
> > > > > > >
> > > > > > > in a router that have under his process an Area type NSSA will
> convert
> > > > the
> > > > > > > Type 7 LSA to Type 5 when going from NSSA to the Backbone Area.
> > > > > > >
> > > > > > > there are no election for ABR or ASBR, if your router have under
> his
> > > > process
> > > > > > > more then one area then he is ABR, if he have redistribution (or
> > > > originating
> > > > > > > a default route) then he is ASBR.
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > On Nov 10, 2007 8:45 PM, Joseph Saad <
> joseph.samir.saad@gmail.com>
> > > > wrote:
> > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > When I have 2 ABR's for an NSSA. The elected Type 7 to Type 5
> LSA
> > > > > > > > translator shows the route in the routing table as N2 while
> the
> > > > other
> > > > > > > > ABR shows it as E2 route.
> > > > > > > >
> > > > > > > > I can understand why the non-elected ABR shows the route as E2
> > > > > > > > (because it receives both type 7 LSA and type 5 LSA and type 5
> LSA
> > > > > > > > will be preferred).
> > > > > > > >
> > > > > > > > What I can't understand is why the elected router shows the
> route as
> > > > > > > > N2 though it is the one which originated the type 5 LSA and
> already
> > > > > > > > has the type 7 LSA in its database.
> > > > > > > >
> > > > > > > > Can someone shed some light on why such behavior?
> > > > > > > >
> > > > > > > >
> > > >
> _______________________________________________________________________
> > > > > > > > Subscription information may be found at:
> > > > > > > > http://www.groupstudy.com/list/CCIELab.html
> > > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > > Shiran Guez
> > > > > > > MCSE CCNP NCE1
> > > > > > > http://cciep3.blogspot.com
> > > > > > > http://www.linkedin.com/in/cciep3
> > > > > >
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > >
> > > >
> > > > Shiran Guez
> > > > MCSE CCNP NCE1
> > > > http://cciep3.blogspot.com
> > > > http://www.linkedin.com/in/cciep3
> > >
> >
> >
> >
> > --
> >
> >
> >
> > Shiran Guez
> > MCSE CCNP NCE1
> > http://cciep3.blogspot.com
> > http://www.linkedin.com/in/cciep3
>
>
>
> --
>
>
> Shiran Guez
> MCSE CCNP NCE1
> http://cciep3.blogspot.com
> http://www.linkedin.com/in/cciep3
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