The advertising router being reachable or not isn't related to DNA. DNA just
means only the originator can flush the LSA by setting maxage. The result of
my previous example is the same whether or not DNA is set:
R1#sh ip ospf database
OSPF Router with ID (1.1.1.1) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 41 0x80000038 0x00C007 2
2.2.2.2 2.2.2.2 1 (DNA) 0x80000037 0x00B209 2
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
10.0.0.2 2.2.2.2 1 (DNA) 0x80000001 0x0043D6
R1#show ip route ospf
Codes: L - local, 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, su - IS-IS summary, 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, H - NHRP
+ - replicated route, % - next hop override
Gateway of last resort is not set
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/2] via 10.0.0.2, 00:00:41, FastEthernet0/0
R1#show ip ospf database router 2.2.2.2
OSPF Router with ID (1.1.1.1) (Process ID 1)
Router Link States (Area 0)
LS age: 1 (DoNotAge)
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 2.2.2.2
Advertising Router: 2.2.2.2
LS Seq Number: 80000037
Checksum: 0xB209
Length: 48
Number of Links: 2
Link connected to: a Stub Network
(Link ID) Network/subnet number: 2.2.2.2
(Link Data) Network Mask: 255.255.255.255
Number of MTID metrics: 0
TOS 0 Metrics: 1
Link connected to: a Transit Network
(Link ID) Designated Router address: 10.0.0.2
(Link Data) Router Interface address: 10.0.0.2
Number of MTID metrics: 0
TOS 0 Metrics: 1
R1#config t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#int f0/0
R1(config-if)#shut
R1(config-if)#end
R1#
*Dec 16 02:30:10.618: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 on
FastEthernet0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
*Dec 16 02:30:10.978: %SYS-5-CONFIG_I: Configured from console by console
*Dec 16 02:30:12.614: %LINK-5-CHANGED: Interface FastEthernet0/0, changed
state to administratively down
*Dec 16 02:30:13.614: %LINEPROTO-5-UPDOWN: Line protocol on Interface
FastEthernet0/0, changed state to down
R1#show ip route ospf
Codes: L - local, 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, su - IS-IS summary, 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, H - NHRP
+ - replicated route, % - next hop override
Gateway of last resort is not set
R1#show ip ospf database router 2.2.2.2
OSPF Router with ID (1.1.1.1) (Process ID 1)
Router Link States (Area 0)
Adv Router is not-reachable in topology Base with MTID 0
LS age: 1 (DoNotAge)
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 2.2.2.2
Advertising Router: 2.2.2.2
LS Seq Number: 80000037
Checksum: 0xB209
Length: 48
Number of Links: 2
Link connected to: a Stub Network
(Link ID) Network/subnet number: 2.2.2.2
(Link Data) Network Mask: 255.255.255.255
Number of MTID metrics: 0
TOS 0 Metrics: 1
Link connected to: a Transit Network
(Link ID) Designated Router address: 10.0.0.2
(Link Data) Router Interface address: 10.0.0.2
Number of MTID metrics: 0
TOS 0 Metrics: 1
R1#show ip ospf database
OSPF Router with ID (1.1.1.1) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 26 0x80000039 0x00608D 1
2.2.2.2 2.2.2.2 1 (DNA) 0x80000037 0x00B209 2
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
10.0.0.2 2.2.2.2 1 (DNA) 0x80000001 0x0043D6
R1#
Brian McGahan, CCIE #8593 (R&S/SP/Security)
bmcgahan_at_INE.com<mailto:bmcgahan_at_INE.com>
Internetwork Expert, Inc.
http://www.INE.com
From: Routing Freak [mailto:routingfreak_at_gmail.com]
Sent: Saturday, December 15, 2012 4:41 AM
To: Antoine Monnier
Cc: Brian McGahan; ccie99999; Cisco certification
Subject: Re: OSPF ADV Router is not-reachable
Yes LSAs with DNA bit set wont age out in the database. Like the one with the
Virtual Links or else in the Demand Circuit where u usually dont need the
hellos to be sent within the interval but still u need the databases to be
synced
It wont show the ADV router is not reachable in the database if DNA bit is
set. But i would test this once and let u know
about it more.
On Sat, Dec 15, 2012 at 5:47 PM, Antoine Monnier
<mrantoinemonnier_at_gmail.com<mailto:mrantoinemonnier_at_gmail.com>> wrote:
What would happen if those LSAs had the Do Not Age bit set ? Would
those LSAs stay in the database forever ??
On Thu, Dec 13, 2012 at 5:38 PM, Brian McGahan
<bmcgahan_at_ine.com<mailto:bmcgahan_at_ine.com>> wrote:
> That's normal. This is a convergence optimization of OSPF in which it
retains old LSAs until the MAXAGE is reached. The idea is that if the
neighbor temporarily flaps, once they come back and they send a database
descriptor you will realize that you already have their LSAs in the database
from before, and the only thing you need to do is update the neighbor as
reachable and reset the age & checksum. Otherwise OSPF would have to go
through full flooding every time there is a neighbor flap. If you wait an
hour (MAXAGE) you will see the LSA eventually disappear. Normally only the
originator of the LSA can prematurely flush the LSA out of the database by
reflooding with MAXAGE, and if that router is cut off from the entire OSPF
network it cannot flood, hence your case.
>
>
> HTH,
>
> Brian McGahan, CCIE #8593 (R&S/SP/Security)
> bmcgahan_at_INE.com<mailto:bmcgahan_at_INE.com>
>
> Internetwork Expert, Inc.
> http://www.INE.com
>
> -----Original Message-----
> From: nobody_at_groupstudy.com<mailto:nobody_at_groupstudy.com>
[mailto:nobody_at_groupstudy.com<mailto:nobody_at_groupstudy.com>] On Behalf Of
ccie99999
> Sent: Thursday, December 13, 2012 5:56 AM
> To: Cisco certification
> Subject: OSPF ADV Router is not-reachable
>
> Hello friends,
>
> I'm working on OSPF in these days and I don't undertand this thing:
>
> I've a stable topology and I've one router (R3) that is my exit point for my
nssa area..
> R3 indeed is configured as nssa no-summary.
> And in the routers in this area (it's area2) get him as only summary LSAs.
>
> Summary Net Link States (Area 2)
>
> Link ID ADV Router Age Seq# Checksum
> 0.0.0.0 150.1.3.3 1091 0x80000001 0x00BED9
>
> If now I decide to kill R3 (shut all interfaces) and even do a clear of ospf
process, I still see the summary in the ospf database.
>
> If then I check the LSA1 on in it I see ADV Router is not-reachable.
>
> Rack1SW1#show ip ospf database router 150.1.3.3
>
> Adv Router is not-reachable
> LS age: 2292
>
> I don't understand the reason it's still there. Should't be flushed? and why
by design it's not?
>
> thank you
>
>
> --
> @ccie99999
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
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>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
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Received on Sat Dec 15 2012 - 20:30:58 ART
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