From: Arun Arumuganainar (aarumuga@hotmail.com)
Date: Fri Aug 05 2005 - 11:58:19 GMT-3
Hi Shanky
Both Type 3 default route and Type 7 default route will be generated when
you enable "Area 1 nssa default-information-originate no-summary"
You can notice this in "show ip ospf database" . But not on "show ip route
" .
Actually the route selection in OSPF has the following order .
1) Intra Area route ( Routes tagged as O)
2) Inter Area Routes ( Routes Tagged as O IA )
3) External routes ( I am not sure about the order . But I think E1or N1 and
then E2 or N2 )
Note : On a given router there can be either E1/E2 routes or N1/N2 Routes
and not both .
Ok coming back to your question . When you configure like this . Both Type 3
and Type 7 LSAs will be generated . However only type 3 will be installed on
the routing table . This is because type3 information is preferred over Type
5 or Type 7 . I have attached my router trace that tells you every thing .
Hope this helps
router1#sh ip ospf database
OSPF Router with ID (139.10.1.1) (Process ID 100)
Router Link States (Area 120)
Link ID ADV Router Age Seq# Checksum Link count
139.10.1.1 139.10.1.1 164 0x80000032 0x00B8DE 2
139.10.2.2 139.10.2.2 278 0x80000033 0x00C870 1
210.10.10.49 210.10.10.49 5 (DNA) 0x8000000A 0x00CF36 1
Net Link States (Area 120)
Link ID ADV Router Age Seq# Checksum
139.10.120.100 210.10.10.49 1 (DNA) 0x80000002 0x0075E5
Summary Net Link States (Area 120)
Link ID ADV Router Age Seq# Checksum
0.0.0.0 139.10.2.2 17 0x80000001 0x00E6B5 >
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Type 3 Default
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Type-7 AS External Link States (Area 120)
Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 139.10.2.2 17 0x80000001 0x006C9B 0
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Type 5 Default
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
139.10.6.0 139.10.1.1 2 0x800029CA 0x005C86 0
router1#
Routing Table :
router1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter
area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is 139.10.120.2 to network 0.0.0.0
139.10.0.0/24 is subnetted, 9 subnets
C 139.10.1.0 is directly connected, Loopback0
D EX 139.10.6.0 [170/332800] via 139.10.11.10, 00:00:04, Ethernet1/0
C 139.10.11.0 is directly connected, Ethernet1/0
D 139.10.10.0 [90/409600] via 139.10.11.10, 1d04h, Ethernet1/0
D 139.10.12.0 [90/307200] via 139.10.11.10, 1d04h, Ethernet1/0
D 139.10.20.0 [90/435200] via 139.10.11.10, 1d04h, Ethernet1/0
D EX 139.10.67.0 [170/332800] via 139.10.11.10, 00:00:04, Ethernet1/0
D EX 139.10.69.0 [170/332800] via 139.10.11.10, 00:00:04, Ethernet1/0
C 139.10.120.0 is directly connected, Ethernet0/0
D 200.3.3.0/24 [90/332800] via 139.10.11.10, 22:26:58, Ethernet1/0
O*IA 0.0.0.0/0 [110/11] via 139.10.120.2, 00:00:05, Ethernet0/0
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Type 3 Default will be installed on the routing table .
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Thanks and Regards
Arun
----- Original Message -----
From: "Shanky" <shankyz@gmail.com>
To: "Thomwin Chen" <thomwin_chen@yahoo.com>
Cc: "lab" <ccielab@groupstudy.com>
Sent: Friday, August 05, 2005 1:59 PM
Subject: Re: OSPF NSSA Default Route ??
> yeah I noticed that.. but area 1 nssa default-information-originate
> no-summary also originates Type 3 LSA only ?
> Area 1 nssa no-summary .. generates Type 3
> Area 1 nssa default-information-originate Type 7
> Area 1 nssa default-information-originate no-summary ... Again Type 3 ?
> And what is CMIIW ?
> Thanks
> Shanky
>
>
> On 8/5/05, Thomwin Chen <thomwin_chen@yahoo.com> wrote:
> >
> > Hi Shanky,
> > CMIIW,
> > I think that's because
> > area 1 nssa no-summary generate default route of Type-3 LSA,
> > while area 1 nssa default-information originate generate default route
of
> > Type-7 LSA.
> > Rgds,
> > Thomwin
> >
> > *Shanky <shankyz@gmail.com>* wrote:
> >
> > Hi,
> > I was just doing some NSSA Stuff and noticed the foll.
> > 1. area # nssa no-summary generates a default route into the NSSA area
> > even
> > when there is no default route on the ABR. The default route is type N2
> > (As
> > it should be) but the cost is goverened by the area # default-cost.
> > 2. Using the area # nssa default-information-originate metric 10
> > metric-type 2 does not override the default route being injected into
area
> > 1
> > by area # nssa no-summary even though the area # default-cost is changed
> > to
> > 100.
> > So that essentially means that the default route injected by area #
> > no-summary is always preferred ?
> > Am I missing something here ?
> > TIA
> > Shanky
> >
> > _______________________________________________________________________
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