ISIS: max-lsp-lifetime & lsp-refresh-interval

How to find it on Doc CD
Some one pls help me navigate it. The above link i found via google

Related Commands

Command	Description
max-lsp-lifetime (IS-IS)	Sets the maximum time that link-state packets (LSPs) can remain in a router's database without being refreshed.

max-lsp-lifetime (IS-IS)

To set the maximum time that link-state packets (LSPs) can remain in a router's database without being refreshed, use the max-lsp-lifetime command in router configuration mode. To restore the default lifetime, use the no form of this command.

max-lsp-lifetime seconds

no max-lsp-lifetime

Syntax Description

seconds

Lifetime of the LSP in seconds. The range is 1 to 65535 seconds; the default is 1200 seconds (20 minutes).

Defaults

1200 seconds (20 minutes)

Command Modes

Router configuration

Command History

Release	Modification
10.3	This command was introduced.

Usage Guidelines

If the lifetime is exceeded before a refresh LSP arrives, the LSP is dropped from the database.

You might need to adjust the maximum LSP lifetime if you change the LSP refresh interval with the lsp-refresh-interval (IP) command. LSPs must be periodically refreshed before their lifetimes expire. The value set for the lsp-refresh-interval command should be less than the value set for the max-lsp-lifetime command; otherwise, LSPs will time out before they are refreshed. If you misconfigure the LSP lifetime to be too low compared to the LSP refresh interval, the software will reduce the LSP refresh interval to prevent the LSPs from timing out.

You might prefer higher values for each command in order to reduce control traffic, at the expense of holding stale LSPs from a crashed or unreachable router in the database longer (thus wasting memory) or increasing the risk of undetected bad LSPs staying active (very rare).

Examples

The following example configures an LSP lifetime of 40 minutes:

router isis

 max-lsp-lifetime 2400

Related Commands

Command	Description
lsp-refresh-interval (IS-IS)	Sets the link-state packet (LSP) refresh interval.

lsp-refresh-interval (IS-IS)

To set the link-state packet (LSP) refresh interval, use the lsp-refresh-interval command in router configuration mode. To restore the default refresh interval, use the no form of this command.

lsp-refresh-interval seconds

no lsp-refresh-interval

Syntax Description

seconds

Interval (in seconds) at which LSPs are refreshed.The range is 1 to 65535 seconds. The default value is 900 seconds (15 minutes).

Defaults

900 seconds (15 minutes)

Command Modes

Router configuration

Command History

Release	Modification
10.3	This command was introduced.

Usage Guidelines

The refresh interval determines the rate at which Cisco IOS software periodically transmits in LSPs the route topology information that it originates. This is done to keep the database information from becoming too old.

LSPs must be periodically refreshed before their lifetimes expire. The value set for the lsp-refresh-interval command should be less than the value set for the max-lsp-lifetime command; otherwise, LSPs will time out before they are refreshed. If you misconfigure the LSP lifetime to be too low compared to the LSP refresh interval, the software will reduce the LSP refresh interval to prevent the LSPs from timing out.

Reducing the refresh interval reduces the amount of time that undetected link state database corruption can persist at the cost of increased link utilization. (This is an extremely unlikely event, however, because there are other safeguards against corruption.) Increasing the interval reduces the link utilization caused by the flooding of refreshed packets (although this utilization is very small).

Examples

The following example configures the IS-IS LSP refresh interval to be 1080 seconds (18 minutes):

router isis

 lsp-refresh-interval 1080

Related Commands

Command	Description
max-lsp-lifetime (IS-IS)	Sets the maximum time that link-state packets (LSPs) can remain in a router's database without being refreshed.

max-lsp-lifetime (IS-IS)

To set the maximum time that link-state packets (LSPs) can remain in a router's database without being refreshed, use the max-lsp-lifetime command in router configuration mode. To restore the default lifetime, use the no form of this command.

max-lsp-lifetime seconds

no max-lsp-lifetime

Syntax Description

seconds

Lifetime of the LSP in seconds. The range is 1 to 65535 seconds; the default is 1200 seconds (20 minutes).

Defaults

1200 seconds (20 minutes)

Command Modes

Router configuration

Command History

Release	Modification
10.3	This command was introduced.

Usage Guidelines

If the lifetime is exceeded before a refresh LSP arrives, the LSP is dropped from the database.

You might need to adjust the maximum LSP lifetime if you change the LSP refresh interval with the lsp-refresh-interval (IP) command. LSPs must be periodically refreshed before their lifetimes expire. The value set for the lsp-refresh-interval command should be less than the value set for the max-lsp-lifetime command; otherwise, LSPs will time out before they are refreshed. If you misconfigure the LSP lifetime to be too low compared to the LSP refresh interval, the software will reduce the LSP refresh interval to prevent the LSPs from timing out.

You might prefer higher values for each command in order to reduce control traffic, at the expense of holding stale LSPs from a crashed or unreachable router in the database longer (thus wasting memory) or increasing the risk of undetected bad LSPs staying active (very rare).

Examples

The following example configures an LSP lifetime of 40 minutes:

router isis

 max-lsp-lifetime 2400

ISIS: Jumbo Frames enabling causes high CPU Load !

Back in this post we mentioned how changing mtu causes ISIS neighborship to go down.
This was remedied by have the same clns mtu on both peers.

However this might cause another problem.
Every 10secs hello are sent out to neighbors with frames of size of the clns mtu.
This is done by padding data onto the frames.
This is called hello padding.

To optimize CPU cycles we can disable Hello Padding.

Either using router level cmd or Interface level cmd
router isis
no hello padding multi-point

OR

int s2/0.1 multipoint
no isis hello padding

Also configure the peer

int s2/0
no isis hello padding

ISIS: avoid DIS election and CSNP transmission

int f0/0
isis network point-to-point

Trackback

ISIS: Redstribution between L1 and L2

router isis
redistribute isis ip level-2 into level-1 distribute-list 100

ip access-list extended 100
permit ip any any

The above must be done at ABR, This will allow all L2 routes to be seen in L1 as ia

ISIS: ip mtu different ! neighborship not formed !

If we have different mtu between two neighbors ISIS neighborship doesnt come up.
More here on CCO support forum.

However, while I was reading up for CCIE, I found a workaround.

if we leave the ip mtu to be different but change the clns mtu to match up, the ISIS neighborship comes up.

R1 s2/0 -- R2 s2/0

R1

int s2/0

mtu 17001

clns mtu 9216

R2

int s2/0

mtu 17008

clns mtu 9216

Back-to-Back FR

PE1
frame-relay switching
int s2/0
encap frame-relay
no frame-relay inverse-arp
no keepalive
ip add 1.1.1.1 255.255.255.0
frame-relay map ip 1.1.1.2 100 broadcast
no shut

ASBR1
frame-relay switching
int s2/2
encap frame-relay
no frame-relay inverse-arp
no keepalive
ip add 1.1.1.2 255.255.255.0
frame-relay map ip 1.1.1.1100 broadcast
no shut

The Point is for back to back FR
1) we must disable keepalives , else PVC shows DELETED
2) we must use same DLCI ( in our e.g 100) , else it doesnt work.

ISIS: Router level config takes precedence over Interface level config

Lets say i have this setup
ASBR1 s2/2 --> PE1 s2/0

I want to run ISIS on this interface at Level-2 only.

This wont work
ASBR1
router isis
is-type level-2

int s2/2
ip router isis

PE1
router isis
is-type level-1

int s2/0
ip router isis
isis circuit-type level-2

It seems that on PE1 the Router ISIS (is-type ) cmd takes precedence over int s2/0 ( isis circuit-type) cmd

Strange isn't it , but that ISIS for you.

Once I modified the is-type to level-1-2 ( the default) on PE1, the neighborship came up.

Conclusion: Router ISIS (is-type ) cmd takes precedence over int s2/0 ( isis circuit-type) cmd

OSPF : RFC 2328 / RFC 1583

The default for calculating summary route's cost is RFC 1583.
RFC 2328 uses a different method .
Cisco conforms to both but RFC 1583 is default.

So to use RFC 2328 instead

specify following
router ospf 1
no compatible rfc1583

Reduce OSPF LSA Flooding v/s Prevent OSPF LSA Flooding.

Earlier I mentioned how to prevent LSA flooding using interface level cmd ip ospf database-filter all out.

Now supposedly, you want to reduce flooding instead of preventing it :-) (Symantecs of Stupid English)

you would apply this cmd
ip ospf flood-reduction

Jumbo Frames and MTU and OSPF neighbor ship

The moment one changes mtu on ONLY one end of the link to support Jumbo Frames ( > 9000 bytes) , when OSPF is restarted it will fail to form adjacency since MTU mismatch will occur.

To ignore MTU mismatch, specify ip ospf mtu-ignore on both ends of the link.

OSPF gotchas

Trackback

Lots of gotchas for OSPF.
Must read !

More here (based on Narbik's WB, But I wouldnt care)

Prevent Flooding of OSPF LSA Broadcasts

Trackback

int s0/0.100
ip ospf database-filter all out

Will allow receiving Hello and LSA from peer
But wont sent out our LSA to them. Our Hellos are still sent out.

==> WE form adjacency with peer. WE get their LSA and install in our routing table
==>Peer forms adjacency with us. peer doesnt get our LSA and hence doesnt see our routes.
==> One way Traffic Flow.... Can be useful in Redundant links / FR Hub n Spoke Topology

The Biggest difference between passive-interface and database-filter is with passive-interface, even hellos are not sent out. So no adjacency and no one way communication.

ignore lsa mospf ==> Do not generate syslog for Type 6 (MOSPF) packets

trackback

And also on CCO

Cisco routers do not support LSA Type 6 MOSPF packets, and they generate syslog messages if they receive such packets. If the router is receiving many MOSPF packets, you might want to configure the router to ignore the packets and thus prevent a large number of syslog messages.

Remember Type 6 LSA = MOSPF LSA

Quickest Convergence without using any L3 (OSPF) features

Trackback

carrier-delay msec 0

the default is 2sec for a link to signal failure.
With carrier-delay msec 0 , the change is signaled immediately for Routing protocols to take their course of action.

ip ospf retransmit-interval

From CCO link

Q. What is the link-state retransmit interval, and what is the command to set it?

A. OSPF must send acknowledgment of each newly received link-state advertisement (LSA). It does this by sending LSA packets. LSAs are retransmitted until they are acknowledged. The link-state retransmit interval defines the time between retransmissions. You can use the command ip ospf retransmit-interval to set the retransmit interval. The default value is 5 seconds.

sh ip ospf int s2/2
Serial2/2 is up, line protocol is up
Internet Address 172.16.111.2/24, Area 13
Process ID 1, Router ID 10.1.1.100, Network Type POINT_TO_POINT, Cost: 64
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

(config-if)#ip ospf retransmit-interval 60

sh ip ospf int s2/2 | in Retransmit
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 60

OSPF LSA flooding pacing

The CCO link explains

ASBR1(config-router)#timers pacing ?
flood OSPF flood pacing timer
lsa-group OSPF LSA group pacing timer
retransmission OSPF retransmission pacing timer

Feature Overview

In rare situations, you might need to change Open Shortest Path First (OSPF) packet-pacing default timers to mitigate CPU or buffer utilization issues associated with flooding very large numbers of link-state advertisements (LSAs). The OSPF Update Packet-Pacing Configurable Timers feature allows you to configure the rate at which OSPF LSA flood pacing, retransmission pacing, and group pacing updates occur.

Configuring OSPF flood pacing timers allows you to control interpacket spacing between consecutive link-state update packets in the OSPF transmission queue. Configuring OSPF retransmission pacing timers allows you to control interpacket spacing between consecutive link-state update packets in the OSPF retransmission queue. Cisco IOS software groups the periodic refresh of LSAs to improve the LSA packing density for the refreshes in large topologies. The group timer controls the interval used for group LSA refreshment; however, this timer does not change the frequency that individual LSAs are refreshed (the default refresh occurs every 30 minutes).

The default are

LSA group pacing timer 240 secs ==> timers pacing lsa-group
Interface flood pacing timer 33 msecs ==> timers pacing flood
Retransmission pacing timer 66 msecs ==> timers pacing retransmission

OSPF : Configure with Highest Level Security !

=> Must use md5 authentication instead of the three types available ( null, normal,md5)
i.e
router ospf 1
area 0 authentication message-digest

int f0/0
ip ospf message-digest 1 md5 CISCO

OR

int f0/0
ip ospf authentication message-digest
ip ospf message-digest 1 md5 CISCO

OSPF Stub Host

router ospf 1
area 2 stub no-summary

BGP Features

Rack1R3#sh run | b r bgp
router bgp 500
neighbor 192.10.1.254 maximum-prefix 7500 100 restart 15
!

Rack1R3#sh ip bgp neighbor 192.10.1.254 | in (Max|Thres)
Maximum prefixes allowed 7500
Threshold for warning message 100%, restart interval 15 min
Rack1R3#

ISIS: TE

router isis
metric-style wide
mpls traffic-eng tunnel level-2
mpls traffic-eng tunnel router-id lo0

==> Side Effects
If there is a router somewhere else that you missed out configuring "metric-style wide" , ISIS adj will go down,

Ref: INE Workbook VOl2 V1.0 Lab 7 Task 5.4 ( Traffic Engineering)

############Alternative ####################################
configure the R3 router with foll
router isis
metric-style transition

Here is why

metric-style transition

To configure a router to generate and accept both old-style and new-style TLVs (TLV stands for type, length, and value object), use the metric-style transition command in router configuration mode.

metric-style transition {level-1 | level-2 | level-1-2}

Syntax Description

level-1	Enables this command on routing level 1.
level-2	Enables this command on routing level 2.
level-1-2	Enables this command on routing levels 1 and 2.

Defaults

IS-IS traffic engineering extensions include new-style TLVs with wider metric fields than old-style TLVs. By default, the MPLS traffic engineering image generates old-style TLVs only. To do MPLS traffic engineering, a router needs to generate new-style TLVs.