Spanning Tree Protocol (STP) Convergance

Two great articles that I highly recommend you read to get a deeper understanding of STP. I have been so busy with work and personal things, that It has taken time away from me being able to update this blog.  Hence why I am posting links to other sites. Never stop learning. I am studying for my switch Exam and would like to take the Exam sometime in late December.

1. Understanding STP Convergence, Part I - INE
2. Understanding STP Convergence, Part II - INE

Cisco Nexus 2000 and 5000: Configuration and Troubleshooting

Great Video on Cisco Nexus 2000 and 5000 switches. The video is geared towards configuration and troubleshooting. Please note that the video is two years old and config sync along with the L3 daughter cards have been release by Cisco.

http://www.youtube.com/watch?v=T6ty_38bJpc

Nexus - Config Sync

When you have two Nexus devices connected to each other via a VPC lpeer link, I have found it useful to have Config Sync enabled.  If you don't have config sync enabled, you will need to update each 5k separately and that is a pain at times. Additionally, if you make a change to one 5k and not the other, it will drop the connection. For example, you update the vlan associated with a switchport on Nexus5596_01, and not Nexus5596_02, it will down the port until Nexus5596_02 is updated. For this lab we are going to use Figure 1. Unfortunatley you cant simulate a switch in GNS3 so you will need to get your hands on some Nexus gear. 

Figure 1 - Nexus Lab

We will use the VPC Keep alive interface for this which is really cat6 cable connected between the switches on the mgmt interface on the back side.

Configurations:

Nexus5596_02# config t

Nexus5596_02(config)# configure sync
Nexus5596_02(config-sync)# switch-profile 5596 (This is what name you want to assigned to the profile)
Nexus5596_02(config-sync-sp)# sync-peers destination 192.168.1.1 (Peer device IP address)

Nexus5596_01# config t
Nexus5596_01(config)# configure sync
Nexus5596_01(config-sync)# switch-profile 5596
Nexus5596_01(config-sync-sp)# sync-peers destination 192.168.1.2

 Verifications:

 Nexus5596_02# show cfs peers

Physical Fabric
-------------------------------------------------------------------------
 Switch WWN              IP Address
-------------------------------------------------------------------------
 20:00:54:7f:ee:28:c3:00 192.168.1.2                             [Local]
                         Nexus5596_02
 20:00:54:7f:ee:25:08:80 192.168.1.1

Total number of entries = 2

Nexus5596_02#

Using the new feature: 

Nexus5596_02# config t

Enter configuration commands, one per line.  End with CNTL/Z.
Nexus5596_02(config)# configure sync
Nexus5596_02(config-sync)# switch-profile 5596
Switch-Profile started, Profile ID is 1
Nexus5596_02(config-sync-sp)# interface eth 101/1/12
Nexus5596_02(config-sync-sp-if)# switchport access vlan 100
Nexus5596_02(config-sync-sp-if)# verify (Optional)
Verification Successful
Nexus5596_02(config-sync-sp)# commit (Committing your changes to this device and the peer device)
Verification successful...
Proceeding to apply configuration. This might take a while depending on amount of configuration in buffer.
Please avoid other configuration changes during this time.
Commit Successful
Nexus5596_02(config-sync)# end
Nexus5596_02#

Nexus5596_01# show run int eth 101/1/12

!Command: show running-config interface Ethernet101/1/12
!Time: Fri Oct 19 04:30:13 2012

version 5.1(3)N1(1a)

interface Ethernet101/1/12
  switchport access vlan 100

Nexus5596_01#

Additional views:

If you don't want to commit your changes, they are stored on the switch untill you commit and you can view them.

Nexus5596_02(config)# config t

Nexus5596_02(config)# configure sync
Nexus5596_02(config-sync)# switch-profile 5596
Switch-Profile started, Profile ID is 1
Nexus5596_02(config-sync-sp)# interface ethernet 101/1/13
Nexus5596_02(config-sync-sp-if)# description example_of_not_commiting
Nexus5596_02(config-sync-sp-if)# end

Nexus5596_02# show switch-profile buffer

switch-profile  : 5596
----------------------------------------------------------
Seq-no  Command
----------------------------------------------------------
1       interface Ethernet101/1/13
1.1       description example_of_not_commiting

Further Reading:

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/system_management/502_n1_1/Cisco_n5k_system_mgmt_cg_rel_502_n1_1_chapter3.html

FCOE vs. iSCSI

Good Video

http://www.youtube.com/watch?v=Z14G-hc45Qw&feature=related

A Day in the Life in a Cisco Connected Classroom

Great Video for those interested in what Cisco is doing beyond the router and switch world. Cisco is just great..

http://www.youtube.com/watch?v=XowBo7tGJbI&feature=channel&list=UL

Passed CCNP-Route 642-902

Got my first exam done... 895 out of 1000. Now starting on the Switch exam. Hopefully take that test sometime in late December...

OSPF Packet Format

Packet Format: Taken from,

http://docwiki.cisco.com/wiki/Open_Shortest_Path_First 

This is useful when you are looking at a packet capture of an OSPF packet. Same can be said for any packet format visualization of any protocol. I am reviewing some OSPF reading material and figured I would post this.

All OSPF packets begin with a 24-byte header, as illustrated in Figure: OSPF Packets Consist of Nine Fields.

Figure: OSPF Packets Consist of Nine Fields

The following descriptions summarize the header fields:

• Version number - Identifies the OSPF version used.
• Type - Identifies the OSPF packet type as one of the following:
  • Hello - Establishes and maintains neighbor relationships.
  • Database description - Describes the contents of the topological database. These messages are exchanged when an adjacency is initialized.
  • Link-state request - Requests pieces of the topological database from neighbor routers. These messages are exchanged after a router discovers (by examining database-description packets) that parts of its topological database are outdated.
  • Link-state update - Responds to a link-state request packet. These messages also are used for the regular dispersal of LSAs. Several LSAs can be included within a single link-state update packet.
  • Link-state acknowledgment - Acknowledges link-state update packets.
• Packet length - Specifies the packet length, including the OSPF header, in bytes.
• Router ID - Identifies the source of the packet.
• Area ID - Identifies the area to which the packet belongs. All OSPF packets are associated with a single area.
• Checksum - Checks the entire packet contents for any damage suffered in transit.
• Authentication type - Contains the authentication type. All OSPF protocol exchanges are authenticated. The authentication type is configurable on per-area basis.
• Authentication - Contains authentication information.
• Data - Contains encapsulated upper-layer information.