CCIE RS – Written – L2 – Implement and Troubleshoot VLANs
VLAN – Virtual LAN
- Administratively defined subset of switch ports that are in the same broadcast domain
- Broadcast domain – devices that can receive broadcast sent by another device
- Best Practice – 1 to 1 relationship between IP subnet and VLAN
Configuration
- Vlan [id]
- Under interface > switchport access vlan [id]
- Modify VLAN operational state (L2 only)
- Can be suspended globaly for entire VTP or to local switch
- Vlan [id] > state suspend (global) | shutdown (local)
Access Ports
Belongs and carries traffic for only 1 VLAN
Configuration
interface > switchport access vlan [#]
VLAN Database
- Vlan 0 – Reserved, not available for use
- Vlan 1 – Default vlan for all access ports
- Cannot be deleted or pruned
- Vlan 4095 – Reserved, not available for use
Switch#sh vlan
VLAN Name Status Ports
—- ——————————– ——— ——————————-
1 default active Gi0/0, Gi0/1, Gi0/2
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
—- —– ———- —– —— —— ——– —- ——– —— ——
1 enet 100001 1500 – – – – – 0 0
1002 fddi 101002 1500 – – – – – 0 0
1003 tr 101003 1500 – – – – – 0 0
1004 fdnet 101004 1500 – – – ieee – 0 0
1005 trnet 101005 1500 – – – ibm – 0 0
Primary Secondary Type Ports
——- ——— —————– ——————————————
Switch#
Normal VLAN
1 – 1001
- Can be advertised with VTPv1 and 2
- Configured in vlan database, global config
- Details stored in vlan.dat
- Can be pruned
1002 – 1005 Special uses
- Cannot be pruned
- 1002 fddi-default
- 1003 token-ring-default
- 1004 fddinet-default
- 1005 trnet-default
Extended VLAN
1006 – 4094
VTPv1 and 2 must be in transparent mode
Voice VLAN
Enables access ports to carry traffic from an IP Phone
- Portfast is automatically enabled when voice vlan is configured
- Not disabled if voice vlan is removed
Configure how the Cisco IP Phone carries voice traffic:
- vlan-id —Configure the phone to forward all voice traffic through the specified VLAN. By default, the Cisco IP Phone forwards the voice traffic with an IEEE 802.1Q priority of 5. Valid VLAN IDs are 1 to 4094.
- dot1p —Configure the phone to use IEEE802.1p priority tagging for voice traffic and to use the default native VLAN (VLAN 0) to carry all traffic. By default, the Cisco IP Phone forwards the voice traffic with an IEEE 802.1p priority of 5.
- none —Allow the phone to use its own configuration to send untagged voice traffic.
- untagged —Configure the phone to send untagged voice traffic.
