What is a VLAN and how does it relate to a RHEL system.

1. VLANs in
Red Hat Enterprise Linux
Raghu Udiyar
Technical support engineer
Red Hat
1 VLANs & you | Raghu Udiyar

2. First, LAN?
● Local Area Network
● Uses Ethernet for Layer 2 communication
● using MAC addresses
● ARP is used for IP -> MAC
● ARP uses broadcast
● LAN = 1 Broadcast domain
● A short refresher on how this works
2 VLANs & you | Raghu Udiyar

3. Port 1 A : f3:a3:34:
Port 2 B : f2:de:34:
This mac is D
Port 3 C : f1:d1:23
On port 4
Port 4 D : f3:a4:56
Who is 192.x.x.x Hey, that's me
Mac is f3:a4:x:x:x
3 VLANs & you | Raghu Udiyar

4. To recap
● A–B–C–D
● A -> D
● ARP broadcast, D is IP 192.x.x.x what is MAC?
● D replies with MAC
● A sends to switch
● Switch looks up the address in the MAC table
● Switch sends to D
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5. Any questions?
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6. VLANs
● Splits a LAN into multiple LANs
● Into multiple broadcast domains
● Splits single switch into multiple switches
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7. Port 1 A : f3:a3:34:
Port 2 B : f2:de:34:
Port 3 C : f1:d1:23
Port 4 D : f3:a4:56
B
Trunk
B
B
B B
7 VLANs & you | Raghu Udiyar

8. VLAN - Advantages
● Flexibility - No physical restrictions
● Security – layer 2 separation
● Cost effective
● Reduce size of broadcast domains
8 VLANs & you | Raghu Udiyar

9. How does this work?
● 802.1q protocol
● VLAN “Tags”
VLAN ID Ethernet Frame
● VLAN 50, 100, etc (1 – 4094)
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10. Type of Ports
● Access port
SW Ethernet
PC1
Vid Ethernet
Vlan id is stripped
Ethernet
PC2
Vid Ethernet
SW
10 VLANs & you | Raghu Udiyar

11. Type of Ports
● Trunk Ports
v Et
SW SW
v Et
v Et
Trunk Ports
Carries all VLAN's
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12. Native Vlan
v Et
SW Et SW
v Et
v Et v Et
Native Vlan
Ethernet frame with no Vlan id get's the native VLAN
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13. Any questions?
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14. Vlans in RHEL
● Access
● Trunk
● Vlan interface :
RHEL
eth0.40
eth0.100 eth0.40 eth0.100 eth0.8
eth0.8
eth0 native vlan
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15. Use case 1 :
SW1
Httpd
Payroll
eth0.40
eth0
SW2
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16. Use Case 2 :
Hypervisor with two guests
VM1 VM2
VLAN10 VLAN20
eth0
Trunk
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17. Demo - Assigning a Vlan ID
● # vconfig add eth0 7
● # ip addr add dev eth0.7 192.168.0.1/24 brd +
● # ip link set dev eth0.7 up
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18. Troubleshooting
● Misconfiguration
● Check switch
● Misunderstanding of concepts
● Access/Trunk
● Native Vlan
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19. Any questions?
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20. Thank You