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--- icnd1:trunking_and_vlans [2024/04/26 22:41]
114.119.149.71 old revision restored (2023/11/01 13:41)
+++ icnd1:trunking_and_vlans [2024/05/14 20:56] (current)
114.119.158.167 old revision restored (2023/12/07 09:21)
@@ Line 1: / Line 1: @@
 ====== Trunking and VLANs ======
-VLANs create separate broadcast domains and isolates traffic to it's own VLAN. Switches will not forward traffic out ports that aren't in their VLAN. Basically, traffic from VLAN 10 cannot reach VLAN 20. Makes grouping traffic pretty easy. For example you may group ACCOUNTING and IT machines into different VLANs.
+VLANs create separate broadcast domains and isolates traffic to it's own VLAN. Switches will not forward traffic out ports that aren't in their VLAN. Basically, traffic from VLAN 10 cannot reach VLAN 20.
-Trunking is the act of carrying data from multiple VLANs over a medium. So a trunk port is a port capable of carrying traffic from specified/any VLANs. This is useful if in a multi-switch environment or inter-vlan routing.
+Trunking carries data from multiple VLANs over a medium. So a trunk port is a port capable of carrying traffic from specified/any VLANs. This is useful if in a multi-switch environment or inter-vlan routing / RoAS w/out a Layer3 Switch.
+===== Notes =====
+ISL is largely unsupported. 802.1Q is the IEEE standard and most adopted.
+<code>switchport trunk encapsulation isl|dot1q</code>
+.1Q:
+  * -Frames are tagged with a VLAN ID Field
+    * Both ISL and .1Q tag a 12bit VLAN Field
+  * -Untagged frames are sent to the NATIVE VLAN on the receiving port.
+  * -It's best practice to have the same NATIVE VLANs set on each side to avoid inconsistencies.
 ===== Configuration =====
@@ Line 87: / Line 96: @@
 </code>
+===== Command reference =====
+----
+<code>
+Switch(config-if)#switchport mode ?
+  access   Set trunking mode to ACCESS unconditionally
+  dynamic  Set trunking mode to dynamically negotiate access or trunk mode
+  trunk    Set trunking mode to TRUNK unconditionally
+Switch(config-if)#switchport mode dynamic ?
+  auto       Set trunking mode dynamic negotiation parameter to AUTO
+  desirable  Set trunking mode dynamic negotiation parameter to DESIRABLE
+Switch(config-if)#switchport trunk allowed vlan add 99
+Switch#show interfaces trunk
+Port        Mode         Encapsulation  Status        Native vlan
+Fa0/24      desirable    n-802.1q       trunking      1
+Gig0/1      on           802.1q         trunking      1
+Port        Vlans allowed on trunk
+Fa0/24      1-1005
+Gig0/1      1-1005
+Port        Vlans allowed and active in management domain
+Fa0/24      1,2,3,900,990
+Gig0/1      1,2,3,900,990
+Port        Vlans in spanning tree forwarding state and not pruned
+Fa0/24      1,2,3,900,990
+Gig0/1      1,2,3,900,990
+Switch#show vlan brief
+VLAN Name                             Status    Ports
+---- -------------------------------- --------- -------------------------------
+    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
+                                                Fa0/17, Fa0/18, Fa0/19, Fa0/20
+                                                Fa0/21, Fa0/22, Fa0/23, Gig0/2
+    VLAN0002                         active    Fa0/13, Fa0/14
+    VLAN0003                         active    Fa0/15, Fa0/16
+  ENG                              active
+  TEST                             active
+fddi-default                     active
+token-ring-default               active
+fddinet-default                  active
+trnet-default                    active    </code>

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