IOS Packaging

Starting with version 12.3, Cisco introduced a new IOS packaging system for routers and switches.

Here are some links from cisco for detailed explanation:
Cisco IOS Packaging Product Bulletin
IOS Packaging, main page
Cisco IOS Packaging Customer Q&A

Troubleshooting High CPU Utilization

Cisco 7500 Series Routers, Troubleshooting TechNotes

* High CPU Utilization in Exec and Virtual Exec Processes

* The show processes Command

* Troubleshooting High CPU Utilization Due to Interrupts

* Troubleshooting High CPU Utilization due to Processes

* Troubleshooting High CPU Utilization in IP Input Process

* Troubleshooting High CPU Utilization on Cisco Routers

* Understanding VIP CPU Running at 99% and Rx-Side Buffering

* What Causes %SYS-3-CPUHOG Messages?

IOS Syslog facilities

Logging and debugging messages are the cornerstone of troubleshooting.

There are 4 possible destinations for Logging:
1.Console
2.Monitor
3.Buffer
4.Host
+plus SNMP

R1(config)#do sh logging
Syslog logging: enabled (9 messages dropped, 1 messages rate-limited, 0 flushes, 0 overruns, xml disabled)
Console logging: level debugging, 33 messages logged, xml disabled
Monitor logging: level debugging, 0 messages logged, xml disabled
Buffer logging: disabled, xml disabled
Logging Exception size (8192 bytes)
Count and timestamp logging messages: disabled
Trap logging: level informational, 38 message lines logged

Descriptions for the fields in the output above.

When troubleshooting in High CPU utilization situations, and you have to use debugging, make sure to disable or "level-limit" the console and monitor logging facilities. Instead use the buffered logging facility to record the debug output and view it with "show logging". This will allow the CPU to process the log messages in a high utilization environment.

To use a syslog server and set the log-level:

R1(config)# logging host
R1(config)# logging trap ?
<0-7> Logging severity level
alerts Immediate action needed (severity=1)
critical Critical conditions (severity=2)
debugging Debugging messages (severity=7)
emergencies System is unusable (severity=0)
errors Error conditions (severity=3)
informational Informational messages (severity=6)
notifications Normal but significant conditions (severity=5)
warnings Warning conditions (severity=4)

Reference:
Troubleshooting and Fault Management Commands @ Cisco
Troubleshooting High CPU Utilization on Cisco Routers @ Cisco

Cisco Router boot configuration

File Systems:
system: (RAM, where running-config is kept)
nvram: (NVRAM, where startup-config is saved)
bootflash: (Internal Flash memory)
slot0: (First PCMCIA slot)
slot1: (Second PCMCIA slot)

Copying:
#copy ftp: system:running-config
#copy ncp: system:running-config
#copy tftp: system:running-config

#copy ftp: nvram:startup-config
#copy rcp: nvram:startup-config
#copy tftp: nvram:startup-config

#copy system:running-config nvram:startup-config

Booting:

#show bootvar (verify the contents of the CONFIG_FILE environment variable.)
#boot config dest-flash-url (Set the CONFIG_FILE environment variable.)

#boot network ftp:[[[//[username[:password]@]location]/directory]
/filename]
#boot network rcp:[[[//[username@]location]/directory]/filename]
#boot network tftp:[[[//location]/directory]/filename]
#service config (Enable the router to download config-files at startup)

#boot system

Other Useful commands:
#service compress-config
#boot buffersize bytes (The buffer that holds the configuration file is usually the size of NVRAM. Larger configurations need larger buffers. )
(config)#config-register value
#dir [flash-filesystem:]

Examples
#copy system:running-config tftp://172.16.1.130/istanbul-config
#copy system:running-config ftp://netadmin1:mypass@172.16.101.101/Ankara-config
#copy rcp://netadmin1@172.16.101.101/host1-confg system:running-config
#copy slot0:4:ios-upgrade-1 nvram:startup-config


Ref: Rebooting and Reloading - Configuring Image Loading Characteristics @ Cisco
Cisco IOS Conf. Fundamentals Command Reference Boot Commands

BGP Attributes

Well-known Mandatory
Origin
AS-Path
Next-Hop

Well-Known Discretionary
Local-Preference
Atomic aggregate

Optional Transitive
Community
Aggregator

Optional Nontransitive
MED (Multiexit Discriminator)

BGP Case Studies @ Cisco

DHCP serving/relaying

Anatomy of getting an address from DHCP

1. Client broadcasts DHCP DISCOVER message
2. Server replies with DHCP OFFER
3. Client asks formally for the offered address with DHCP REQUEST
4. Server acknowledges with DHCP ACK
5. Client sends out a gratuitous ARP to check if the IP address is used, if not starts using it.

Setup a DHCP Server
# ip dhcp pool {pool_name}
# network { network } { mask | prefix }
# default-router { hostname | ip }
# dns-server { hostname | ip }
# domain-name { name }
# lease { days, hours... }
etc..

* Exclude addresses from pools with # ip dhcp exclude-address {low_address} {high_address}
** Addresses are always assigned on the interface that has an IP address in the same subnet as the pool.

Acting as DHCP Relay
Use following interface configuration command to forward certain broadcasts.

R1 (config-if) # ip help-address {destination server}

Troubleshooting
# sh ip dhcp binding
# clear ip dhcp binding
# sh ip dhcp pool
# sh ip dhcp server statistics

IS-IS Authentication

1-) Clear text:

# router isis
# isis password MyPaSS

2-) Area password:

# router isis
# area-password YesAnAreaPass

3-) Domain password:

# router isis
# domain-password ThisWouldBeEasy

4-) MD5 Authentication:

Use it either under an interface or the whole router process; first create your key-chain. (Eg: keyISIS)

# interface s1/0
# isis authentication key-chain keyISIS
# isis authentication mode md5

or under router process

# router isis
# isis authentication key-chain keyISIS
# isis authentication mode md5

you can also limit it to level-1 or level-2 and send-only

# isis authentication mode md5 { level-1 | level-2 }
# isis authentication send-only { level-1 | level-2 }

IS-IS Pseudonode and DIS (Designated IS)

In IS-IS a broadcast link itself is modeled as a pseudo-node that connects all attached routers to a star topology.
The pseudo-node is represented by the DIS (Designated router)



On broadcast type links a DIS is elected for both Level-1 and Level-2, if they exist.
A router with highest priority or highest SNPA (MAC,DLCI,..) address is selected as DIS.
Default priority is 64. (can be between 0-127)
DIS election can be preempted, any priority change will take effect immediately.

There is no backup DIS (unlike OSPF) and all routers in a LAN establish adjacencies with each other and the DIS.

The DIS creates and maintains the pseudo-node LSP.
This LSP contains the adjacent ISs, just like the network lsa in OSPF.

EIGRP Stub Router

Stub routers in EIGRP will only send limited information to their ONLY neighbor, a core (EIGRP) router.
This way the router will minimize memory and processor utilization.
Also helps speeding up convergence because a stub router answers to queries as inaccessible, thus limiting the query range and preventing SIA situations.

Syntax:
eigrp stub [receive-only | connected | redistributed | static | summary]

Distance command

Filter and change AD of routes before they enter the RIB.

1-) Protocol independent "distance" command:
distance AD advertising_router_ip wildcard access-list

You can have multiple distance commands.
Also a default distance that will apply to any routes not defined in another "distance" command.

2-) Protocol dependent:

With this you can change the AD of an external/internal route for EIGRP, external/inter-area/intra-area route for OSPF and so on.

Eg:
distance ospf external 125 (sets all the external OSPF routes that are learned with and AD of 125)

OSPF Network Types

OSPF Communication:
Multicast 224.0.0.5: All OSPF Neighbors listen
224.0.0.6: Only DR and BDR listen

OSPF Network Types:

RIP Lab advises from a CCIE

These quick-and-dirty notes are not from me, I came across a post on a blog, and thought it could be useful..

So, taking note for future reference..

Opening Move:
————-
conf t
router rip
ver 2
no auto
pass def

do sh ip int br
network
no pass

!Broadcast v2 update:
———————
(config-if)#ip rip v2-broadcast

!Unicast updates:
—————–
1- send unicast updates
(config-router)#neighbor A.B.C.D “Neighbor address”
2- stop broadcast/multicast updates
passiv

Differet subnets:
—————–
(config-router)#NO validate-update-source

!check split horizon

Show commds:
————
Sh ip protocols
Routing Information Sources:
Gateway Distance Last Update

Killing the Route:
——————
1- Distribute list
2- offset list (poison the metric)
3- admin distance (poison the distance)

Reference