From: Volkov, Dmitry (IDS Canada) (dmitry_volkov@ca.ml.com)
Date: Wed Jul 16 2003 - 18:29:23 GMT-3
Alex,
In the Lab I asked question about, R4 has only one interface belonging to
"0" and other interface
where OSPF is not running and requirement - to assign last interface to
area 49.
Lets determine first what does it mean : "interface in area X" ?
I believe it means (at least) that router can send hello packets out
of this interface and to form adjacency with neighbor on the same area.
area0----(intA)R4(intB)---backbone
if You redistr static to backbone and put "area range 49 <..>" router will
send LSU with new LSA 5 out to area 0
with "area 0" as Area ID field inside OSPF packet LSU/DD header (assuming
it's formed adjacency with peer in area 0).
Router will not send any hello packets to BB which You want to be area 49.
Even if You have another int in area 49 on the same router it will not send
anything out to BB.
So - Why do You say that interface intB in area 49 ??
Yes router creates LSA in area 49 in Data base but perfix described BB
network is in LSA 5,
LSAs are being sent out of router inside LSU/DD which has area ID field in
header.
LSA itself doesn't know what is it area ID.
I can't agree that when injecting external prefixes in OSPF You put that
interface where they are
coming from into OSPF area.
Any way it's subject of terminology ;)
Dmitry
> -----Original Message-----
> From: Alexander Arsenyev (GU/ETL)
> [mailto:alexander.arsenyev@ericsson.com]
> Sent: Wednesday, July 16, 2003 11:52 AM
> To: 'ccielab@groupstudy.com'
> Subject: RE: RE: How to put interface in OSPF area without
>
>
> The documented purpose of "area <number> range <whatever>" is
> as per Your post below.
>
> In the context of Your task I used it to create area 49 LSAs
> on router and that is the
> purpose of "area 49 range" command on R4.
>
> I have to respectfully disagree second time regarding Type 5
> LSAs. Put is this way -
> if R4 has only 2 interfaces in 2 areas (o0 and 49) then it's
> impossible to determine that prefix covering "net Backbone"
> (or part of it) is coming from area 49. However, if You
> delete area 0 on R4 this prefix will still stay in R4 LSA
> database and logically speaking it is coming from area 49
> because there will be no other area!
Prefix doesn't go anywhere. So it doesn't make sence.
> Same happens if You add one more interface on R4, assign it
> to area 49 and establish adjacency with some other router(s)
> via this interface. Then delete area 0 on R4 and display LSA
> database on adjacent router(s). If you see "net Backbone"
> there - Your task is complete: there is one and only area 49
> on R4 and it contains "net Backbone" (or part of it, it
> depends on static routes configured on R4).
Again, this prefix will be in DB on other router as LSA 5.
"sh ip ospf data" will not tell that this preffix i area 49
> Interestingly, I've just thought that it is possible to
> propagate whole "net Backbone" by the way of multiple
> specific static routes redistributed into OSPF - in the
> extreme case it could be multiple host routes. Referring to
> Your example below, it could be 254 routes of sort "ip route
> 150.50.10.$x 255.255.255.255 eth0/0" where x is in range 1...254.
>
> Thanks//Cheers
> Alex
>
> -----Original Message-----
> From: Volkov, Dmitry (IDS Canada) [mailto:dmitry_volkov@ca.ml.com]
> Sent: 15 July 2003 22:41
> To: Alexander Arsenyev (GU/ETL)
> Cc: ccielab@groupstudy.com
> Subject: RE: RE: How to put interface in OSPF area without
>
>
> Interesting, How did You get that :
> "The command "area 49 range <whatever>" creates area 49 LSAs
> on the router
> and this is
> the purpose of "area 49" command" ???
> I never heard about such interpretation of this command and I
> always thought
> that MAIN and only purpose
> of "area range" - to configure route aggregation on the ABRs and/or to
> filter inter-area routes
> (in case when "not-advertise" on that end)
>
> Anyway it's true - "area X range network mask" creates LSA 1
> (on ASBR) and
> LSA 1 & 3 (on ABR).
>
> However I don't not agree with your concslusion that LSA 5
> (redistributed
> static) has any relation to area X (49).
> You don't need even to have any redistribution on ABR to
> generate LSA 1 & 3
> if You put "area X range"
> (I assume that no any connected interfaces belong to "X")
>
> I don't see any evidence that backbone network on R4 belongs
> to area 49.
>
> So technically speaking despite LSA 1 for area 49 is created, the
> requirement to
> "put R4s backbone interface in OSPF area 49" is NOT completed.
>
> I think this requirement is wrong. There is no way to put
> network into area
> without "network" command
>
> Thanks,
> Dmitry
>
> area 0 ----(eth0/1)R4(et0/0)-----Backbone
>
> interface Loopback0
> ip address 11.11.11.1 255.255.255.0
> ip ospf network point-to-point
> interface Ethernet0/0
> ip address 150.50.10.1 255.255.255.0
> interface Ethernet0/1
> ip address 192.168.15.1 255.255.255.0
> !
> router ospf 1
> log-adjacency-changes
> area 49 range 150.50.10.0 255.255.255.0
> redistribute static subnets
> network 11.11.11.0 0.0.0.255 area 123
> network 192.168.15.0 0.0.0.255 area 0
> !
> ip route 150.50.10.111 255.255.255.255 Ethernet0/0
>
> OSPF Router with ID (11.11.11.1) (Process ID 1)
>
> Router Link States (Area 0)
>
> Link ID ADV Router Age Seq#
> Checksum Link count
> 11.11.11.1 11.11.11.1 426 0x80000002 0x9947 1
> 192.168.15.15 192.168.15.15 426 0x80000020 0x2EA 1
>
> Net Link States (Area 0)
>
> Link ID ADV Router Age Seq# Checksum
> 192.168.15.15 192.168.15.15 427 0x80000001 0x265B
>
> Summary Net Link States (Area 0)
>
> Link ID ADV Router Age Seq# Checksum
> 11.11.11.0 11.11.11.1 421 0x80000011 0xD612
>
> Router Link States (Area 49)
>
> Link ID ADV Router Age Seq#
> Checksum Link count
> 11.11.11.1 11.11.11.1 431 0x80000002 0xFDFC 0
>
> Summary Net Link States (Area 49)
>
> Link ID ADV Router Age Seq# Checksum
> 11.11.11.0 11.11.11.1 427 0x80000001 0xF602
> 192.168.15.0 11.11.11.1 412 0x80000003 0x8313
>
> Router Link States (Area 123)
>
> Link ID ADV Router Age Seq#
> Checksum Link count
> 11.11.11.1 11.11.11.1 437 0x80000001 0x6663 1
>
> Summary Net Link States (Area 123)
>
> Link ID ADV Router Age Seq# Checksum
> 192.168.15.0 11.11.11.1 412 0x80000003 0x8313
>
> Type-5 AS External Link States
>
> Link ID ADV Router Age Seq# Checksum Tag
> 150.50.10.111 11.11.11.1 437 0x80000001 0x102C 0
> r4#
>
> r4#sh ip ospf data route
>
> OSPF Router with ID (11.11.11.1) (Process ID 1)
>
> Router Link States (Area 0)
>
> LS age: 463
> Options: (No TOS-capability, DC)
> LS Type: Router Links
> Link State ID: 11.11.11.1
> Advertising Router: 11.11.11.1
> LS Seq Number: 80000002
> Checksum: 0x9947
> Length: 36
> Area Border Router
> AS Boundary Router
> Number of Links: 1
>
> Link connected to: a Transit Network
> (Link ID) Designated Router address: 192.168.15.15
> (Link Data) Router Interface address: 192.168.15.1
> Number of TOS metrics: 0
> TOS 0 Metrics: 10
>
>
> LS age: 466
> Options: (No TOS-capability, DC)
> LS Type: Router Links
> Link State ID: 192.168.15.15
> Advertising Router: 192.168.15.15
> LS Seq Number: 80000020
> Checksum: 0x2EA
> Length: 36
> Number of Links: 1
>
> Link connected to: a Transit Network
> (Link ID) Designated Router address: 192.168.15.15
> (Link Data) Router Interface address: 192.168.15.15
> Number of TOS metrics: 0
> TOS 0 Metrics: 10
>
>
>
> Router Link States (Area 49)
>
> LS age: 472
> Options: (No TOS-capability, DC)
> LS Type: Router Links
> Link State ID: 11.11.11.1
> Advertising Router: 11.11.11.1
> LS Seq Number: 80000002
> Checksum: 0xFDFC
> Length: 24
> Area Border Router
> AS Boundary Router
> Number of Links: 0
>
>
>
> Router Link States (Area 123)
>
> LS age: 482
> Options: (No TOS-capability, DC)
> LS Type: Router Links
> Link State ID: 11.11.11.1
> Advertising Router: 11.11.11.1
> LS Seq Number: 80000001
> Checksum: 0x6663
> Length: 36
> Area Border Router
> AS Boundary Router
> Number of Links: 1
>
> Link connected to: a Stub Network
> (Link ID) Network/subnet number: 11.11.11.0
> (Link Data) Network Mask: 255.255.255.0
> Number of TOS metrics: 0
> TOS 0 Metrics: 1
>
>
>
> > -----Original Message-----
> > From: Alexander Arsenyev (GU/ETL)
> > [mailto:alexander.arsenyev@ericsson.com]
> > Sent: Tuesday, July 15, 2003 12:32 PM
> > To: ccielab@groupstudy.com
> > Subject: RE: RE: How to put interface in OSPF area without
> >
> >
> > I respectfully disagree. The command "area 49 range
> > <whatever>" creates area 49 LSAs on the router, and this is
> > the purpose of "area 49" command, not to summarise anything
> > out from area 49.
> > What I infer from the diagram is that there are just 2
> > interfaces on the R4 and "Backbone interface" should be put
> > into OSPF process and in area 49. If area 49 already present
> > in this router or there are more interfaces You should tell
> > us about this. My solution creates LSA type 5 for "Backbone
> > interface" and this LSA is present in area 49 though this is
> > kind of almost non-existent area since it has no any
> > interfaces in it and link count in area 49 router LSA on R4 is 0.
> > Nevertheless, I believe if router LSA exists for area 49 it
> > means that area itself exists.
> >
> > Strangely enough, area 49 LSA stay there if even I delete
> > "area 49 range" statement and clear ip ospf process, but this
> > is not a main problem. The main problem is to create area 49
> > without "network" statement and if someone knows better way I
> > would love to hear.
> >
> > Thanks//Cheers
> > Alex
>
>
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