For the first problem, I can see in routing table the concept of Forward
metric, if bandwidth are unequal, first route has :
IR_AS200_AREA1#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "ospf 1", distance 110, metric 100, candidate default path, type
NSS
A extern 2, forward metric 10
Redistributing via ospf 1
Last update from 193.0.0.2 on Ethernet0, 00:00:00 ago
Routing Descriptor Blocks:
* 193.0.0.2, from 192.168.108.2, 00:00:00 ago, via Ethernet0
Route metric is 100, traffic share count is 1
If I shut down the ethernet link, the second route goes up :
IR_AS200_AREA1#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "ospf 1", distance 110, metric 100, candidate default path, type
NSS
A extern 2, forward metric 64
Redistributing via ospf 1
Last update from 2.0.0.1 on Serial0, 00:00:00 ago
Routing Descriptor Blocks:
* 2.0.0.1, from 192.168.108.4, 00:00:00 ago, via Serial0
Route metric is 100, traffic share count is 1
Does the concept of forward metric influence the choose of routes for NSSA ?
""Stephane LITKOWSKI"" a icrit dans le message de news:
[EMAIL PROTECTED]
> Hi all,
>
> I have some questions about Type 7 LSA default-routes propagated by ABRs.
> Consider a NSSA with two ABRs. Each ABR propagate a default route with a
> cost of 100 (commands are : area 1 nssa default-originate & area 1
> default-cost 100).
> On a Internal router directly connected to each ABR, I can see that only
one
> default route is in the routing table :
>
> O*N2 0.0.0.0/0 [110/100] via 193.0.0.2, Ethernet0
>
> But the two LSA are in the database :
>
> IR_AS200_AREA1#sh ip ospf database nssa-external
>
> OSPF Router with ID (192.168.108.3) (Process ID 1)
>
>
> Type-7 AS External Link States (Area 1)
>
> Routing Bit Set on this LSA
> LS age: 1702
> Options: (No TOS-capability, No Type 7/5 translation, DC)
> LS Type: AS External Link
> Link State ID: 0.0.0.0 (External Network Number )
> Advertising Router: 192.168.108.2
> LS Seq Number: 80000001
> Checksum: 0x4F63
> Length: 36
> Network Mask: /0
> Metric Type: 2 (Larger than any link state path)
> TOS: 0
> Metric: 100
> Forward Address: 193.0.0.2
> External Route Tag: 0
>
> LS age: 318
> Options: (No TOS-capability, No Type 7/5 translation, DC)
> LS Type: AS External Link
> Link State ID: 0.0.0.0 (External Network Number )
> Advertising Router: 192.168.108.4
> LS Seq Number: 80000003
> Checksum: 0xF37B
> Length: 36
> Network Mask: /0
> Metric Type: 2 (Larger than any link state path)
> TOS: 0
> Metric: 100
> Forward Address: 2.0.0.1
> External Route Tag: 0
>
> My first question is, why does the IR choose one default route and not the
> both ? With more investigation, I can see that it prefer the link with the
> highest bandwidth. If I increase the bandwidth of the other link, the
> nexthop change :
>
> O*N2 0.0.0.0/0 [110/100] via 2.0.0.1, Serial0
>
> if bandwidth are equal, the both routes are introduced :
>
> O*N2 0.0.0.0/0 [110/100] via 193.0.0.2, Ethernet0
> [110/100] via 2.0.0.1, Serial0
>
> Why does it consider cost of the link ?
>
> My other question is, on the ABR. I can see that the 0.0.0.0 LSA are in
the
> database. The First one is not computed because selforiginated but why the
> other is not computed ? (It's a type 7 LSA , not type 3).
>
>
> Thanks for help.
>
> --
> Stephane LITKOWSKI
> Student in a French computer science school
> EPITA Telecom & Network specialization (Paris, FRANCE)
> CCNA + CCNP
> EMail : [EMAIL PROTECTED]
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=52123&t=52122
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