My CISCO Journal

Cisco IOS devices support a number of banners that are presented to users when they use the console line or when they connect remotely using telnet or SSH. They are often used to inform users about their legal rights. It might be a good idea to present a banner to users who are trying to connect to your device, here are some items you might want to think about:

here’s a good example on the website of the California Technology Agency that gives you more information about what a good banner should contain and some sample texts. Before you implement any banners, make sure to check your legal council first. Having said that, let’s look at the different banners…

Different Banners

Cisco IOS routers support a number of banners, here they are:

We’ll take a look at how to configure these different banners now.

We’ll start with the message of the day banner that will be presented to anyone accessing the router:

R1(config)#banner motd #
Enter TEXT message.  End with the character '#'.
Authorized users only, violaters will be shot on sight! #

The # symbol is a start and stop character. You can use any other character if you want. This is what the MOTD banner looks like:

R1#exit

R1 con0 is now available

Press RETURN to get started.

Authorized users only, violaters will be shot on sight!

A nice and welcome banner that everyone will see…let’s move on to the login banner now.

The login banner is presented to users that access the router remotely using telnet or SSH:

R1(config)#banner login $ Authenticate yourself! $

Let’s try it out:

R1#telnet 1.1.1.1
Trying 1.1.1.1 ... Open

Authorized users only, violaters will be shot on sight!  Authenticate yourself!

Above you see that the login banner is displayed after the MOTD banner. It would have been better if I added some empty lines so that the login banner would show up below the MOTD banner.

The exec banner is shown just before the exec prompt:

R1(config)#banner exec #
Enter TEXT message.  End with the character '#'.
You are connected to line $(line) at router $(hostname)
#

This time I added an extra line in the banner and I also used some operators like $(line) and $(hostname). Let’s see what that looks like:

R1#exit

R1 con0 is now available

Press RETURN to get started.

Authorized users only, violaters will be shot on sight!
You are connected to line 0 at router R1

As you can see it shows to which line I am connected (line 0 is the console) and the hostname of my router (R1). One more banner to go!

The last banner is used for reverse telnet connections. Reverse telnet can be used to access the console of another device by connecting the AUX port of the router to the console port of another router. This allows you to ‘telnet’ into the console port of another router.

R1(config)#banner incoming $
Enter TEXT message.  End with the character '$'.
This is a banner for Reverse Telnet
$

We’ll have to configure the AUX port in order to test it:

R1(config)#line aux 0
R1(config-line)#transport input telnet

We will enable telnet on the aux port, now we’ll have to check what line our AUX port uses:

R1#show line 
*Mar  1 01:48:09.495: %SYS-5-CONFIG_I: Configured from console by console
R1#show line 
   Tty Typ     Tx/Rx    A Modem  Roty AccO AccI   Uses   Noise  Overruns   Int
*     0 CTY              -    -      -    -    -      2       1     0/0       -
     97 AUX   9600/9600  -    -      -    -    -      0       0     0/0       -
     98 VTY              -    -      -    -    -      2       0     0/0       -
     99 VTY              -    -      -    -    -      0       0     0/0       -
    100 VTY              -    -      -    -    -      0       0     0/0       -
    101 VTY              -    -      -    -    -      0       0     0/0       -
    102 VTY              -    -      -    -    -      0       0     0/0       -

Now we can reverse telnet to the AUX port like this:

R1#telnet 1.1.1.1 6097
Trying 1.1.1.1, 6097 ... Open

Authorized users only, violaters will be shot on sight! 
This is a banner for Reverse Telnet

As you can see it presents us the “incoming banner”. I hope this has been helpful to you to understand the banners!

This great, post has been taken from Rene Molenaar website. Please visit and do support his awesome and brilliant website: http://networklessons.com/network-management/how-to-configure-cisco-ios-banners/

Today i am posting an awesome post link from www.routerfreak.com it related to Understanding Ethernet Jumbo Frames. Here is the link to the article: http://www.routerfreak.com/understanding-ethernet-jumbo-frames/

Some of the things discussed in this article are:

Standard Ethernet Framce

Jumbo Frames

Why do we need Jumbo Frames

Problems with Jumbo Frames

How to use Jumbro Frames

Advantages of Jumbo Frames

• To reduce the global routing table size
• To preserve the IP address space

• Inside Local: the host address inside the network that we want to translate
• Outside Local: translated address of the outside hosts, as seen inside their network
• Inside Global: the addresses used to translate the inside addresses
• Outside Global: addresses of outside hosts as seen on the outside

!
ip subnet-zero
!

!--- These are the IKE policies.

crypto isakmp policy 1

!--- Defines an Internet Key Exchange (IKE) policy.
!--- Use the crypto isakmp policy command
!--- in global configuration mode.
!--- IKE policies define a set of parameters to be used
!--- during the IKE phase I negotiation.

 hash md5
authentication pre-share

!--- Specifies pre-shared keys as the authentication method.

crypto isakmp key Chris123 address 165.228.212.83

!--- Configures a pre-shared authentication key,
!--- used in global configuration mode.

!

!--- These are the IPSec policies.

crypto ipsec transform-set rtpset esp-des esp-md5-hmac

!--- A transform set is an acceptable combination
!--- of security protocols and algorithms.
!--- This command defines a transform set
!--- that has to be matched on the peer router.

!
crypto map rtp 1 ipsec-isakmp

!--- Creates a crypto map and indicates that IKE will be used
!--- to establish the IPSec SAs for protecting
!--- the traffic specified by this crypto map entry.


set peer 165.228.212.83

!--- Use the set peer command to specify an IPSec peer in a crypto map entry.

set transform-set rtpset

!--- Configure IPSec to use the transform set "rtpset"
!--- that was defined previously.

 match address 115
 exit

!--- Include the private-network-to-private-network traffic
!--- in the encryption process.

interface Ethernet 0
 description --- Ethernet LAN ---
 ip address 192.168.0.254 255.255.255.0

 ip virtual-reassembly
 ip tcp adjust-mss 1420

!
!
ip dhcp excluded-address 192.168.0.251 192.168.0.254
!
ip dhcp pool lan
network 192.168.0.0 255.255.255.0
default-router 192.168.0.254
dns-server 192.168.0.254
lease infinite

interface ATM0
 description --- Telsra ADSL ---
 no ip address
 no shutdown
 no atm ilmi-keepalive
 pvc 8/35
  tx-ring-limit 3
  encapsulation aal5snap
  pppoe-client dial-pool-number 1


interface Dialer0
 description --- Telsra ADSL ---
 ip address negotiated
 ip mtu 1460
 ip nat outside
 ip virtual-reassembly
 encapsulation ppp
 ip tcp adjust-mss 1420
 dialer pool 1
 dialer-group 1
 ppp chap hostname tareet0@direct.telsra.net
 ppp chap password 233981
 crypto map rtp

ip nat inside source list NAT interface Dialer0 overload

ip nat inside source route-map nonat interface Dialer0 overload

Step # 1 Download Secure CRT from : http://thepiratebay.se/torrent/7438817/VanDyke.SecureCRT.v7.0.0.326-ZWT(x86)
Install the software according to its default directory setting.

Step # 2 Open your GNS3 Edit --- > Preference Box menu , from here go to General --- > Terminal Settings


Step # 3 Select the Secure CRT according to your OS from Preconfigurated terminal commands drop down box


In my case , as i am using 64-bit OS, i have selected SecureCRT(Windows 64-bit), once selected, click the Use button and you are good to use CRT! Great..

As a demonstration, i have opened my all routers in a single sweet looking window of Secure CRT :


I hope this post was helpful for you. Please let me know your feedback, your questions are welcomed in the comments box below.

Router>	User EXEC mode
Router#	Privileged EXEC mode
Router(config)#	Configuration mode
Router(config-if)#	Interface level (within configuration mode)
Router(config-router)#	Routing engine level (within configuration mode)
Router(config-line)#	Line level (vty, tty, async) within configuration mode

Software Version	- IOS software version (stored in flash)
Bootstrap Version	- Bootstrap version (stored in Boot ROM)
System up-time	- Time since last reboot
System restart info	- Method of restart (e.g. power cycle, crash)
Software image name	- IOS filename stored in flash
Router Type and Processor type	- Model number and processor type
Memory type and allocation (Shared/Main)	- Main Processor RAM - Shared Packet I/O buffering
Software Features	- Supported protocols / feature sets
Hardware Interfaces	- Interfaces available on router
Configuration Register	- Bootup specifications, console speed setting, etc.

some other interesting commands worth knowing on a CISCO IOS are :


R1#show file systems
File Systems:

     Size(b)     Free(b)      Type  Flags  Prefixes
           -           -    opaque     rw   archive:
           -           -    opaque     rw   system:
       57336       57051     nvram     rw   nvram:
           -           -    opaque     rw   null:
           -           -   network     rw   tftp:
*   16777212    16777212     flash     rw   flash:
           -           -     flash     rw   slot0:
           -           -    opaque     wo   syslog:
           -           -    opaque     rw   xmodem:
           -           -    opaque     rw   ymodem:
           -           -   network     rw   rcp:
           -           -   network     rw   pram:
           -           -   network     rw   ftp:
           -           -   network     rw   http:
           -           -   network     rw   scp:
           -           -   network     rw   https:
           -           -    opaque     ro   cns:


R1#show inventory
NAME: "2691 chassis", DESCR: "2691 chassis"
PID:                   , VID: 0.1, SN: XXXXXXXXXXX


R1#show diag
2691 Backplane EEPROM:
        PCB Serial Number        : XXXXXXXXXXX
        Processor type           : 66
        Top Assy. Part Number    : 800-09616-02
        Board Revision           : F0
        Fab Part Number          : 28-4226-06
        Deviation Number         : 65535-65535
        Manufacturing Test Data  : FF FF FF FF FF FF FF FF
        RMA Number               : 255-255-255-255
        RMA Test History         : FF
        RMA History              : FF
        Chassis Serial Number    : XXXXXXXXXXX
        Chassis MAC Address      : c000.1310.0000
        MAC Address block size   : 32
        Field Diagnostics Data   : FF FF FF FF FF FF FF FF
        Hardware Revision        : 0.1
        Number of Slots          : 1
        EEPROM format version 4
        EEPROM contents (hex):
          0x00: 04 FF C1 8B 58 58 58 58 58 58 58 58 58 58 58 09
          0x10: 66 40 02 58 C0 46 03 20 00 25 90 02 42 46 30 85
          0x20: 1C 10 82 06 80 FF FF FF FF C4 08 FF FF FF FF FF
          0x30: FF FF FF 81 FF FF FF FF 03 FF 04 FF C2 8B 58 58
          0x40: 58 58 58 58 58 58 58 58 58 C3 06 C0 00 13 10 00
          0x50: 00 43 00 20 C5 08 FF FF FF FF FF FF FF FF 41 00
          0x60: 01 01 01 FF FF FF FF FF FF FF FF FF FF FF FF FF
          0x70: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
Slot 0:
        C2691 Mother board 2FE(TX)-3W Port adapter, 2 ports
        Port adapter is analyzed
        Port adapter insertion time unknown
        EEPROM contents at hardware discovery:
        PCB Serial Number        : XXXXXXXXXXX
        Processor type           : 66
        Top Assy. Part Number    : 800-09616-02
        Board Revision           : F0
        Fab Part Number          : 28-4226-06
        Deviation Number         : 65535-65535
        Manufacturing Test Data  : FF FF FF FF FF FF FF FF
        RMA Number               : 255-255-255-255
        RMA Test History         : FF
        RMA History              : FF
        Chassis Serial Number    : XXXXXXXXXXX
        Chassis MAC Address      : c000.1310.0000
        MAC Address block size   : 32
        Field Diagnostics Data   : FF FF FF FF FF FF FF FF
        Hardware Revision        : 0.1
        Number of Slots          : 1
        Product (FRU) Number     : C2691-2FE
        EEPROM format version 4
        EEPROM contents (hex):
          0x00: 04 FF C1 8B 58 58 58 58 58 58 58 58 58 58 58 09
          0x10: 66 40 02 58 C0 46 03 20 00 25 90 02 42 46 30 85
          0x20: 1C 10 82 06 80 FF FF FF FF C4 08 FF FF FF FF FF
          0x30: FF FF FF 81 FF FF FF FF 03 FF 04 FF C2 8B 58 58
          0x40: 58 58 58 58 58 58 58 58 58 C3 06 C0 00 13 10 00
          0x50: 00 43 00 20 C5 08 FF FF FF FF FF FF FF FF 41 00
          0x60: 01 01 01 FF FF FF FF FF FF FF FF FF FF FF FF FF
          0x70: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

...
cisco RSP4 (R5000) processor with 65536K/2072K bytes of memory
...
16384K bytes of processor board System flash (Read ONLY)

Example 1: Separate DRAM and Packet Memory

... 
cisco RSP4 (R5000) processor with 65536K/2072K bytes of memory
...

Example 2: Combined DRAM and Packet Memory

... 
cisco 2611 (MPC860) processor (revision 0x202) with 29696K/3072K bytes of memory 
...

Example 3: Available Flash Memory

...
cisco RSP4 (R5000) processor with 65536K/2072K bytes of memory
...
16384K bytes of processor board System flash (Read ONLY)

Router#show flash 

System flash directory: 
File   Length   Name/status 
  1    8407884  c2600-io3s56i-mz.121-6 
[8407948 bytes used, 8369268 available, 16777216 total] 
16384K bytes of processor board System flash (Read/Write)

I was working on an assignment involving GLBP implementation for Network Redundancy. I was totally un aware of this Protocol. Although i had some exposure to HSRP but was not aware of GLBP! This was totally an alien concept for me. Thankful to Mr Keith Barker! Who has made an outstanding video on Youtube, covering all the basics of GLBP and giving a detailed overview of its configurations. In this video Keith has covered almost all of the major components related to GLBP. A must watch video for a Network Engineer.







Quick Facts:

• GLBP uses 224.0.0.102 UDP/3222
• GLBP default Hello interval is 3 seconds
• GLBP has virtual MAC 0007.b4xx.xxyy with xx being group number and yy being forwarder number
• GLBP allows up to 4 virtual MAC address per group
• Elected Active Virtual Gateway (AVG) assigns/revokes virtual MAC to/from group members
• Each gateway is an Active Virtual Forwarder (AVF) and answers own ARP request