From: Joseph Saad (joseph.s.saad@gmail.com)
Date: Wed Aug 22 2007 - 11:03:20 ART
I labbed it up. The reflooding occur every 30 minutes.
Most likely the aging occurs every 60 minutes, but I can't think of a way to
test this out.
Cisco IOS Software, 3600 Software (C3640-JK9O3S-M), Version 12.4(16),
RELEASE SOFTWARE (fc1)
*Mar 1 00:21:34.779: OSPF: Rcv LS UPD from 155.1.0.1 on Serial1/0 length 76
LSA count 1
*Mar 1 00:21:34.783: OSPF: Synchronized with 155.1.0.1 on Serial1/0, state
FULL
*Mar 1 00:21:34.783: %OSPF-5-ADJCHG: Process 1, Nbr 155.1.0.1 on Serial1/0
from LOADING to FULL, Loading Done
Rack1R2#debu ip ospf flood
OSPF flooding debugging is on
*Mar 1 00:52:08.207: OSPF: received update from 155.1.0.1, Serial1/0
*Mar 1 00:52:08.207: OSPF: Rcv Update Type 1, LSID 155.1.0.1, Adv rtr
155.1.0.1, age 1, seq 0x80000004
*Mar 1 00:52:08.211: OSPF: Set idb next flood info from 0 (0) to 6507B38C
(4)
*Mar 1 00:52:08.211: OSPF: Add Type 1 LSA ID 155.1.0.1 Adv rtr 155.1.0.1
Seq 80000004 to Serial1/0 flood list
*Mar 1 00:52:08.211: OSPF: Sending update over Serial1/0 without pacing
*Mar 1 00:52:08.211: OSPF: Set idb next flood info from 6507B38C (4) to 0
(0)
*Mar 1 00:52:08.215: OSPF: Remove Type 1 LSA ID 155.1.0.1 Adv rtr 155.1.0.1
Seq 80000004 from Serial1/0 flood list
*Mar 1 00:52:08.215: OSPF: Stop Serial1/0 flood timer
*Mar 1 00:52:10.715: OSPF: Sending delayed ACK on Serial1/0
*Mar 1 00:52:10.715: OSPF: Ack Type 1, LSID 155.1.0.1, Adv rtr 155.1.0.1,
age 1, seq 0x80000004
*Mar 1 00:52:25.283: Update router LSA 155.1.0.2 155.1.0.2 1 80000005
*Mar 1 00:52:25.283: OSPF: Inc retrans unit nbr count index 1 (0/1) to 1/1
*Mar 1 00:52:25.283: OSPF: Set Nbr 155.1.0.1 1 first flood info from 0 (0)
to 6507B354 (5)
*Mar 1 00:52:25.287: OSPF: Init Nbr 155.1.0.1 1 next flood info to 6507B354
*Mar 1 00:52:25.287: OSPF: Add Type 1 LSA ID 155.1.0.2 Adv rtr 155.1.0.2
Seq 80000006 to Serial1/0 155.1.0.1 retransmission list
*Mar 1 00:52:25.287: OSPF: Start Serial1/0 155.1.0.1 retrans timer
*Mar 1 00:52:25.287: OSPF: Set idb next flood info from 0 (0) to 6507B354
(5)
*Mar 1 00:52:25.287: OSPF: Add Type 1 LSA ID 155.1.0.2 Adv rtr 155.1.0.2
Seq 80000006 to Serial1/0 flood list
*Mar 1 00:52:25.291: OSPF: Sending update over Serial1/0 without pacing
*Mar 1 00:52:25.291: OSPF: Flooding update on Serial1/0 to 224.0.0.5 Area 0
*Mar 1 00:52:25.291: OSPF: Send Type 1, LSID 155.1.0.2, Adv rtr 155.1.0.2,
age 1, seq 0x80000006 (0)
*Mar 1 00:52:25.291: OSPF: Create retrans unit 0x6427F214/0x65079EEC 1
(0/1) 1
*Mar 1 00:52:25.295: OSPF: Set nbr 1 (0/1) retrans to 4530 count to 0
*Mar 1 00:52:25.295: OSPF: Set idb next flood info from 6507B354 (5) to 0
(0)
*Mar 1 00:52:25.295: OSPF: Remove Type 1 LSA ID 155.1.0.2 Adv rtr 155.1.0.2
Seq 80000006 from Serial1/0 flood list
*Mar 1 00:52:25.295: OSPF: Stop Serial1/0 flood timer
*Mar 1 00:52:25.299: OSPF: Build router LSA for area 0, router ID
155.1.0.2, seq 0x80000006
*Mar 1 00:52:25.299: Update network LSA 155.1.0.2 155.1.0.2 2 80000001
*Mar 1 00:52:25.299: OSPF: Build network LSA for Serial1/0, router ID
155.1.0.2
*Mar 1 00:52:25.299: OSPF: Build network LSA for Serial1/0, router ID
155.1.0.2
*Mar 1 00:52:25.303: OSPF: Inc retrans unit nbr count index 1 (0/1) to 1/1
*Mar 1 00:52:25.303: OSPF: Set Nbr 155.1.0.1 1 first flood info from
6507B354 (5) to 6507B354 (5)
*Mar 1 00:52:25.303: OSPF: Adjust Nbr 155.1.0.1 1 next flood info to
6507B354
*Mar 1 00:52:25.303: OSPF: Add Typ#e 2 LSA ID 155.1.0.2 Adv rtr 155.1.0.2
Seq 80000002 to Serial1/0 155.1.0.1 retransmission list
*Mar 1 00:52:25.307: OSPF: Set idb next flood info from 0 (0) to 6507B38C
(6)
*Mar 1 00:52:25.307: OSPF: Add Type 2 LSA ID 155.1.0.2 Adv rtr 155.1.0.2
Seq 80000002 to Serial1/0 flood list
*Mar 1 00:52:25.307: OSPF: Start Serial1/0 pacing timer 25 ms
*Mar 1 00:52:25.335: OSPF: Flooding update on Serial1/0 to 224.0.0.5 Area 0
*Mar 1 00:52:25.335: OSPF: Send Type 2, LSID 155.1.0.2, Adv rtr 155.1.0.2,
age 1, seq 0x80000002 (0)
*Mar 1 00:52:25.335: OSPF: Create retrans unit 0x6427F244/0x65079F8C 1
(0/1) 1
*Mar 1 00:52:25.335: OSPF: Set nbr 1 (0/1) retrans to 4868 count to 0
*Mar 1 00:52:25.339: OSPF: Set idb next flood info from 6507B38C (6) to 0
(0)
*Mar 1 00:52:25.339: OSPF: Remove Type 2 LSA ID 155.1.0.2 Adv rtr 155.1.0.2
Seq 80000002 from Serial1/0 flood list
*Mar 1 00:52:25.339: OSPF: Stop Serial1/0 flood timer
*Mar 1 00:52:27.903: OSPF: Received ACK from 155.1.0.1 on Serial1/0
*Mar 1 00:52:27.903: OSPF: Rcv Ack Type 1, LSID 155.1.0.2, Adv rtr
155.1.0.2, age 1, seq 0x80000006
*Mar 1 00:52:27.903: OSPF: Dec retrans unit nbr count index 1 (0/1) to 0/0
*Mar 1 00:52:27.903: OSPF: Free nbr retrans unit 0x6427F214/0x65079EEC 0
total 0. Also Free nbr retrans block
*Mar 1 00:52:27.907: OSPF: Set Nbr 155.1.0.1 1 first flood info from
6507B354 (5) to 6507B38C (6)
*Mar 1 00:52:27.907: OSPF: Adjust Nbr 155.1.0.1 1 next flood info to
6507B38C
*Mar 1 00:52:27.907: OSPF: Remove Type 1 LSA ID 155.1.0.2 Adv rtr 155.1.0.2
Seq 80000006 from 155.1.0.1 retransmission list
*Mar 1 00:52:27.907: OSPF: Rcv Ack Type 2, LSID 155.1.0.2, Adv rtr
155.1.0.2, age 1, seq 0x80000002
*Mar 1 00:52:27.911: OSPF: Dec retrans unit nbr count index 1 (0/1) to 0/0
*Mar 1 00:52:27.911: OSPF: Free nbr retrans unit 0x6427F244/0x65079F8C 0
total 0. Also Free nbr retrans block
*Mar 1 00:52:27.911: OSPF: Set Nbr 155.1.0.1 1 first flood info from
6507B38C (6) to 0 (0)
*Mar 1 00:52:27.911: OSPF: Adjust Nbr 155.1.0.1 1 next flood info to 0
*Mar 1 00:52:27.915: OSPF: Remove Type 2 LSA ID 155.1.0.2 Adv rtr 155.1.0.2
Seq 80000002 from 155.1.0.1 retransmission list
*Mar 1 00:52:27.915: OSPF: Stop nbr 155.1.0.1 retransmission timer
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
subodh.rawat@wipro.com
Sent: Wednesday, August 22, 2007 3:22 PM
To: ccie.xpert@gmail.com
Cc: reto_ccie@yahoo.com; ccielab@groupstudy.com
Subject: RE: IP ospf demand-circuit V/S IP ospf flood reduction ???
Shamim,
I read this in Cisco Press Book "Cisco IOS Cookbook, 2nd Edition".
Section "Recipe 8.18. Reducing OSPF Traffic in Stable Networks".
It reads like
"By default, OSPF will flood the area with all known LSAs every 3,600
seconds (1 hour). This is done as a sort of fail-safe to ensure that
whatever else might happen to the LSA database, it will be corrected at
least once an hour. In most networks this is unnecessary, as OSPF does a
good job of forwarding LSA messages whenever there is a change in the
network. But it is usually safe and may correct pathological conditions
where one or more LSAs have been dropped in the network, which is why
the designers of OSPF included the feature. However, if you are
concerned about the bandwidth overhead on your network, and if your
network is exceptionally stable, you can probably make do without this
fail-safe feature. "
I dont whom to trust; Cisco website or Cisco press book.
Regards
Subodh
________________________________
From: Shamin [mailto:ccie.xpert@gmail.com]
Sent: Wednesday, August 22, 2007 2:55 PM
To: Subodh Singh Rawat (WT01 - TELECOM SERVICE PROVIDER)
Cc: reto_ccie@yahoo.com; ccielab@groupstudy.com
Subject: Re: IP ospf demand-circuit V/S IP ospf flood reduction ???
Dear Subodh,
This is as per cisco website and as far as i know :
Each OSPF LSA has an age, which indicates whether the LSA is still
valid. Once the LSA reaches the maximum age (one hour), it is discarded.
During the aging process, the originating router sends a refresh packet
every 30 minutes to refresh the LSA. Refresh packets are sent to keep
the LSA from expiring, whether there has been a change in the network
topology or not. Checksumming is performed on all LSAs every 10 minutes.
The router keeps track of LSAs it generates and LSAs it receives from
other routers. The router refreshes LSAs it generated; it ages the LSAs
it received from other routers.
http://www.cisco.com/en/US/products/sw/iosswrel/ps1826/products_feature_
guide09186a0080087d4d.html
But I will appreciate if you can clarify me as to the differences
between "ip ospf flood reduction " & " ip ospd demand -circuit"
Regards
Shamin
On 8/22/07, subodh.rawat@wipro.com < subodh.rawat@wipro.com
<mailto:subodh.rawat@wipro.com> > wrote:
Just to correct you: This refreshment of LSA takes place after 1
hour
not 30 minutes.
Subodh
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
Behalf Of
eicc tester
Sent: Wednesday, August 22, 2007 4:38 AM
To: Shamin; Cisco certification
Subject: Re: IP ospf demand-circuit V/S IP ospf flood reduction
???
Hi
"ip ospf flood reduction" just avoid the refreshement of LSA
every 30
minutes.
"ip ospf demand circuit" mean that a link which is under an
OSPF area
, don,t send OSPF hello packet all the time. This avoid the fact
of
bring the circuit (probaly and dial or isdn) just for sent hello
packet
periodically, the neigbhor relations is still maintaned.
Shamin <ccie.xpert@gmail.com> wrote:
Hi All,
Can any one tell me , when the commands "ip ospf flood
reduction" is
used over " ip ospf demand circuit" .
I know that, "Ip ospf demand circuit is used in point to point
connections.
Does that mean, ip ospf flood reduction"
is used in Broadcast and NBMA OSPF networks. I am bit confused
as to
which command to apply in a particular scenario, mainly if the
question
asks to reduce the "paranoid updates" in ospf that occurs every
30mins.
Thanks in advance.
Regards
Shamin
This archive was generated by hypermail 2.1.4 : Sat Sep 01 2007 - 11:32:12 ART