CCIE Pursuit Blog

January 6, 2008

Internetwork Expert Volume III: Lab 1 – Section 2

2 Bridging and Switching

2.1 VLAN Assignments

This is a pretty easy task.  You need to set up sw1 as a VTP server and the remaining switches as VTP clients.  You are then given a list of named VLANs to configure as well as a list of ports with VLAN assignments.

IE refers to the VLANs by VLAN name (i.e. VLAN_B) instead of the VLAN number.  You need to use the number when assigning a port to a VLAN:

sw1(config-if)#swit acc vla ?
  <1-4094>  VLAN ID of the VLAN when this port is in access mode
  dynamic   When in access mode, this interfaces VLAN is controlled by VMPS

sw1(config-if)#swit acc vla VLAN_B
                                                ^
% Invalid input detected at ‘^’ marker.

The initial configurations have shut down most of the ports so there are no trunks negotiated by default, so if you do these tasks in order, be sure to come back and verify VTP and access ports after your trunks are up and VTP has propagated the VLANs.

The IE solution guide shows that they are using “switchport mode access” under the ports.  I don’t see anything in the task that requires this.

My solution:

interface FastEthernet0/1
 switchport access vlan 14

sw1#sh int fa0/1 switch
Name: Fa0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 14 (VLAN_A)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
—output truncated—

IE answer:

interface FastEthernet0/1
 switchport access vlan 14
 switchport mode access

sw1(config-if)#do sh int fa0/1 swit
Name: Fa0/1
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 14 (VLAN_A)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
—output truncated—

2.3 Etherchannel

Simple Etherchannel task.  This subtask is a red herring:

“Use the default native VLAN for this connection.”

Dot1q trunking uses VLAN 1 as the native VLAN by default, so no additional configuration is necessary:

sw1(config)#do sh int po1 trunk

Port        Mode         Encapsulation  Status        Native vlan
Po1         on               802.1q                   trunking      1

Since no channel-group protocol or number was specified in the task,  I used “on” and “1” respectively:

interface FastEthernet0/13
 switchport trunk encapsulation dot1q
 switchport mode trunk
 channel-group 1 mode on

2.3 Trunking

Be careful on this task.  They are asking for two distinct, non-contiguous dot1q trunks.  You can still use “interface range” to shave a little time off of this task though:

sw2(config)#int rang fa0/19,fa0/21
sw2(config-if-range)#swit tru en dot
sw2(config-if-range)#swit mod tru
sw2(config-if-range)#no shut

2.4 Etherchannel

Mind the order of operations for Layer 3 Etherchannels during this task.  The IE solution guide has a nice example of the correct order of operations.  Also, this task asks you to “use all remaining directly connected inter-switch links” between sw2 and sw3 as well as sw2 and sw4.  This gets a little difficult due to the initial configurations setting some of the connected ports in shutdown.  Unless you are given a layer 2 map with all of the inter-switch connections listed in the actual lab, this would be a pain in the ass as you would need to do a “no shut” ports on sw2, sw3, and sw4 to see the connections via “show cdp neighbor”.  Also note that both Layer 3 Etherchannels use a /25 (255.255.255.128) mask.  You’ll discover one of the two initial configuration errors during this task.

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