How to get thourgh the economic slow down? You can spend more time to learn!

Open wide and full (DSCN0634),
originally uploaded by Li-Ji.

I believe many people, no matter in what business, or suffering in any condition, would absolutely have more and more "free time"!

From the brighter side of view, it is a great chance for you to "learn"! I would like to give your some advices:

1. You can spend more time on the Cisco Learning Network. It is a Cisco Official site and so many peoplpe are gathering around discussing and sharing information there about learning and certification.
2. You may invest yourself, or find sponsorship from your company, to enroll some good training courses. For example, try to type "ccnp course" in the "Google Custom Search" box above every post in my blog to find some good CCNP-related training courses.
3. Subscribe to my blog by Email, and let me know what contents you want to read! I will devote myself more to write as many useful post as I can!

To encourage more and more visitors become readers, I prepare some "secret gifts" for you if you do subscribe to my blog by Email successfully (see the top right Email subscription box), before the end of year 2009! Of course, existing readers will also have it!

It only takes 3 simple steps to subscribe to my blog by Email: (1) fill you Email address in the top right box and click submit, then (2) you will receive a confirmation Email, and finally (3) you open that Email and click the confirmation link in it. Done!

Your every readership and feedback mean a lot to me! You can share this information to your friends and colleagues, as much as possible!

Enable VTP to distribute VLAN information, and provide two Virtual LAN (VLAN), using 3 connected switches (CNA-03-004)

CCNA Exploration 4.0, Semester 3, "Enable VTP to distribute VLAN information, and provide two Virtual LAN (VLAN), using 3 connected switches" Packet Tracer 5.0 practice file (CNA-03-004).

• CNA-03-004.pkt, (Backup Link)
• CNA-03-004-sol.pkt, (Backup Link)

The diagram is in fact the same as the previous example. You must have noticed that it is really bothering to add VLANs on switches one after one. In this case, we are going to make use of a special automatic method by IOS itself: the VTP protocol.

VTP stands for VLAN Trunking Protocol. It is a proprietary protocols among Cisco switches to distribute VLAN information.

Although it is not difficult for you to "peep" at "CoreSwitch"'s configuration in this Packet Tracer file, I wish you do not try it. What I want you to feel is to enable VTP only and then observe "Switch1" and "Switch2" getting VLAN information automatically!

In this case, "Switch1" and "Switch2" can play the VTP role as "Client". That is, it listens VLAN information advertised from the VTP "Server" role switches.

Client Configs:

Switch1(config)#vtp mode client
Switch1(config)#vtp domain ccna
Switch1(config)#

Server Configs:

CoreSwitch(config)#vtp mode server
CoreSwitch(config)#vtp domain ccna
CoreSwitch(config)#

Just like the VLAN information, we cannot see them in the running configuration. We can issue "show vtp status" command to check VTP status.

Switch1:

Switch1#show vtp status
VTP Version                     : 2
Configuration Revision          : 4
Maximum VLANs supported locally : 255
Number of existing VLANs        : 7
VTP Operating Mode              : Client
VTP Domain Name                 : ccna
VTP Pruning Mode                : Disabled
VTP V2 Mode                     : Disabled
VTP Traps Generation            : Disabled
MD5 digest                      : 0x9E 0x49 0xD8 0xC7 0xED 0x7C 0xB2 0x01 
Configuration last modified by 20.1.1.101 at 3-1-93 00:01:58
Switch1#

CoreSwitch:

CoreSwitch#show vtp status
VTP Version                     : 2
Configuration Revision          : 4
Maximum VLANs supported locally : 255
Number of existing VLANs        : 7
VTP Operating Mode              : Server
VTP Domain Name                 : ccna
VTP Pruning Mode                : Disabled
VTP V2 Mode                     : Disabled
VTP Traps Generation            : Disabled
MD5 digest                      : 0x9E 0x49 0xD8 0xC7 0xED 0x7C 0xB2 0x01 
Configuration last modified by 20.1.1.101 at 3-1-93 00:01:58
Local updater ID is 20.1.1.101 on interface Vl1 (lowest numbered VLAN interface found)
CoreSwitch#

Providing two Virtual LAN (VLAN), using 3 connected switches (CNA-03-003)

CCNA Exploration 4.0, Semester 3, "Providing two Virtual LAN (VLAN), using 3 connected switches" Packet Tracer 5.0 practice file (CNA-03-003).

• CNA-03-003.pkt, (Backup Link)
• CNA-03-003-sol.pkt, (Backup Link)

This practice is continued from previous Practice 1 and Practice 2. Essentially, we must configure the two "Inter-switch Links" manually as "Trunk Link".

But that's not enough. One thing I have to point out is we also have to declare VLAN 10 and VLAN 20 in the middle switch: "CoreSwitch". We often forget about this when we implement LAN switching.

Why should we do this? This is because of the design of a hardware switch. It cannot "guess" how many VLANs could be there. Switches only separate and forward frames tagged as certain VLANs when it knows those VLANs exist. If we forget to declare them, then the "CoreSwitch" will not recognize frames tagged as VLAN 10 and VLAN 20, and thus drops all frames of them. We lose connectivity for both VLAN 10 and VLAN 20 in the end.

Then why we do not have to "declare" VLAN 10 and VLAN 20 in previous examples? This is because when we configure some switch port as access link of "VLAN 10", Cisco IOS add "VLAN 10" automatically for us. The same thing happens for VLAN 20, too. However, because we do not configure any switch ports in "CoreSwitch" as neither VLAN 10 nor VLAN 20, we have to declare them by ourselves.

CoreSwitch(config)#vlan 10
CoreSwitch(config-vlan)#exit
CoreSwitch(config)#vlan 20
CoreSwitch(config-vlan)#exit
CoreSwitch(config)#

We cannot know from "running-config" about which VLANs are added. We have to issue "show vlan" command to display the VLANs we successfully declared.


Before we add VLANs:

CoreSwitch#show vlan

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa0/1, Fa0/2, Fa0/3, Fa0/4
                                                Fa0/5, Fa0/6, Fa0/7, Fa0/8
                                                Fa0/9, Fa0/10, Fa0/11, Fa0/12
                                                Fa0/13, Fa0/14, Fa0/15, Fa0/16
                                                Fa0/17, Fa0/18, Fa0/19, Fa0/20
                                                Fa0/21, Fa0/22, Fa0/23, Fa0/24
                                                Gig1/1, Gig1/2
1002 fddi-default                     active    
1003 token-ring-default               active    
1004 fddinet-default                  active    
1005 trnet-default                    active    

VLAN Type  SAID       MTU   Parent RingNo BridgeNo Stp  BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1    enet  100001     1500  -      -      -        -    -        0      0
1002 enet  101002     1500  -      -      -        -    -        0      0
1003 enet  101003     1500  -      -      -        -    -        0      0
1004 enet  101004     1500  -      -      -        -    -        0      0
1005 enet  101005     1500  -      -      -        -    -        0      0

CoreSwitch#

After we declared VLANs, we will see the differences:

CoreSwitch#show vlan

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa0/1, Fa0/2, Fa0/3, Fa0/4
                                                Fa0/5, Fa0/6, Fa0/7, Fa0/8
                                                Fa0/9, Fa0/10, Fa0/13, Fa0/14
                                                Fa0/15, Fa0/16, Fa0/17, Fa0/18
                                                Fa0/19, Fa0/20, Fa0/21, Fa0/22
                                                Fa0/23, Fa0/24, Gig1/1, Gig1/2
10   VLAN0010                         active    
20   VLAN0020                         active    
1002 fddi-default                     active    
1003 token-ring-default               active    
1004 fddinet-default                  active    
1005 trnet-default                    active    

VLAN Type  SAID       MTU   Parent RingNo BridgeNo Stp  BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1    enet  100001     1500  -      -      -        -    -        0      0
10   enet  100010     1500  -      -      -        -    -        0      0
20   enet  100020     1500  -      -      -        -    -        0      0
1002 enet  101002     1500  -      -      -        -    -        0      0
1003 enet  101003     1500  -      -      -        -    -        0      0
1004 enet  101004     1500  -      -      -        -    -        0      0
1005 enet  101005     1500  -      -      -        -    -        0      0

CoreSwitch#

Providing two Virtual LAN (VLAN), using 2 connected switches (CNA-03-002)

CCNA Exploration 4.0, Semester 3, "Providing two Virtual LAN (VLAN), using 2 connected switches" Packet Tracer 5.0 practice file (CNA-03-002).

• CNA-03-002.pkt, (Backup Link)
• CNA-03-002-sol.pkt, (Backup Link)

Continuing from previous example, but we add one more switch to do the same thing.

Looking at the only link between the two switches in the diagram, we now have to "mix" frames in the two Virtual LANs (VLANs) going through that link. Of course, if we add up more VLANs, the same link would get more frames belonging to more different VLANs mixing in that link.

Then how can a switch tell which frame belongs to which VLAN? Yes, adding tags on each frame is a great solution! Cisco 2950s and Cisco 2960s support only one type of tagging: IEEE 802.1Q.

If a inter-switch link is mixing frames from different VLANs,  we call it a "Trunk Link". The ports of its both sides are called "Trunk Ports" Just like a real tree, while the "trunk" nourishes branches and leaves, a "trunk link" services several VLANs.

If a switch port is used for one PC or one server only, then we do not have to mix and add tags. These ports are just "normal" Ethernet switch ports without any tagging. We call them "Access Link". The switch ports of its both sides are called "Access Ports".

From the diagram and above discussion, we know we have to configure the only link as "Trunk Link". The simplest way to do so is to "manually" configure both sides of the link into mode "Trunk".

The example is like this:

interface FastEthernet0/11
 switchport mode trunk

The other configuration is just the same as the previous example. You can check the Packet Tracer files yourself!

What is a "Spanning Tree"? Learn it by her song!

The inventor of Spanning Tree algorithm, Dr. Radia Perlman, wrote this "Algorhyme", to explain the essence of "Spanning Tree algorithm" itself. It was published in her book: "Interconnections: Bridges, Routers, Switches, and Internetworking Protocols, 2nd Ed", on page 58.

In the video it also mentioned the "Piano" melody was also by her. Well, I am not sure about it!

Do you have clearer picture of what "Spanning Tree Protocols" is, now?

Algorhyme

I think that I shall never see
A graph more lovely than a tree.

A tree whose crucial property
Is loop-free connectivity.

A tree that must be sure to span
So packets can reach every LAN.

First the root must be selected.
By ID, it is elected.

Least-cost paths from root are traced.
In the tree, these paths are placed.

A mesh is made by folks like me,
Then bridges find a spanning tree.


- Radia Perlman

Go to the following URL of Google Books, then search with keyword "Algorhyme". Then you will get the source page! (On Page 58.)

http://books.google.com/books?id=AIRitf5C-QQC&pg=PA58&vq=spanning+tree&dq=book+interconnections+spanning+tree&source=gbs_search_s&cad=0

How to restore a Cisco IOS Switch back to factory defaults

River view at Tamsui, Taiwan.

Yes, you know what I am talking about! Restoring a switch back to factory defaults is a daily operation of a Cisco Partner's job!

Commands "write erase" or "erase startup-config" followed by a power-off is good enough for IOS routers to go back to factory default state. But this is not true for IOS switches.

Does Cisco's Packet Tracer software support BGP?

Tamshui View (DSC_0217),
originally uploaded by Li-Ji.

I was totally wrong on this post! Please go to this new page instead!

Show IP Protocols: BGP sample practice, in the new Packet Tracer 5.3

I tested. No!

Will BGP be added into it? I do not think so!

Cisco's Packet Tracer software is just for very entry level learners of Cisco and network technologies. It is designed for pre-CCNA or CCNA people's practicing only!

Then how to practice BGP? Maybe "Dynamips" is a good idea!