From Teknologisk videncenter
3 VLANs
3.1 Introducing VLANs
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3.1.2 Types of VLANs
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| Kaldes datavlan for at fremhæve der ikke skal være fx voice eller mgmt trafik på det. Er beregnet til brugerdata
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| Som default er alle porte medlem af et VLAN, på en ny switch er det VLAN 1. VLAN1 kan ikke omdøbes eller slettes. CDP og STP kører som default på default VLAN.
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| Nativ VLAN bruges i IEEE802.1Q trunks til untagged pakker. Best-practice er at bruge andet end VLAN 1 til nativ vlan.
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| Management VLAN bruges til at kontrollere switchen, så der skal sættes en IP adr. på vlan'et.
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- Signaling traffic
- Voice traffic
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3.1.3 Switch Port Membership Modes
VLAN Membership Policy Server
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3.1.4 Controlling Broadcast Domains with VLANs
 Broadcast domain with no VLAN segmentation |
 Controlling broadcast domains with VLANs and Routers |
| Fortæl lidt om hvordan en pakke bliver sendt på tværs af vlans. Med ARP og det hele.
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 Controlling broadcast domains with L3 Switches |
3.2 VLAN Trunking
3.2.1 VLAN Trunks
| Definition of a trunk: A trunk is a point-to-point link between two network devices that carries more than one VLAN.
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3 bits of user priority - Used by the 802.1p standard, which specifies how to provide expedited transmission of Layer 2 frames.
1 bit of Canonical Format Identifier (CFI) - Enables Token Ring frames to be carried across Ethernet links easily.
12 bits of VLAN ID (VID) - VLAN identification numbers; supports up to 4096 VLAN IDs.
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3.2.3 Trunking Modes
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- On Sender DTP frames og bliver i trunk mode
- Dynamic Auto Sender DTP frames, men foreslår ikke trunking
- Dynamic desirable Sender DTP frames, og vil gerne trunke
- Off Sender ikke DTP frames, bruges mod ikke-Cisco udstyr
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3.3 Configuring VLANs and Trunks
3.3.1 Configura VLANs and Trunks Overview
 Configura VLANs and Trunks Overview |
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3.3.3 Manging VLANs
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 Show interface swithcport |
 no switchport access vlan |
| Delete vlan with no vlan vlan-id or delete flash:vlan.dat
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3.3.4 Configure a trunk
 Configura an 802.1Q Trunk - Topology |
 Configura an 802.1Q Trunk - Commands |
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3.4 Troubleshooting VLANs and Trunks
3.4.1 Common Problems with Trunks
 Common problems with trunks |
 Nativ VLAN mismatch - Nativ vlan on S3 = 100 |
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 Incorrect VLAN list - VLAN 20 is not allowed on F0/3 on S1 |
 Incorrect VLAN and Subnet |
3.5 Chapter Summary
3.6.1 Chapter Summary
Links
VLAN Security White Paper
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