VRF Cheat Sheet (Skill 39 / WorldSkills)

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CORE IDEA

* VRF = separate routing tables
* full Layer 3 isolation
* overlapping IPs allowed
* no inter-VRF communication by default

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CREATE VRF

ip vrf 
rd ASN:ID

Example:
ip vrf A
rd 1:1

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ASSIGN INTERFACE

interface g0/0
ip vrf forwarding 
ip address  

Important:

* IP gets removed → reconfigure after VRF assignment
* interface can belong to only one VRF

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STATIC ROUTING

ip route vrf    

Example:
ip route vrf A 0.0.0.0 0.0.0.0 10.0.0.254

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VERIFY ROUTING

show ip route vrf 
show ip vrf

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PING / TESTING

ping vrf  

Example:
ping vrf A 8.8.8.8

Critical:

* without VRF → uses global routing table

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OSPF IN VRF

router ospf  vrf 
network   area 

Each VRF = separate OSPF process

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INTER-VRF COMMUNICATION

Default:

* NOT possible

Options:

* route leaking
* firewall (ASA between VRFs)
* external routing path

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VRF LITE (YOU NEED THIS)

* no MPLS
* local router/switch only
* used in labs / competitions

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COMMON MISTAKES

* interface not in VRF
* forgot to reassign IP after VRF
* missing “vrf” in route command
* ping without VRF
* no default route in VRF
* OSPF configured globally instead of VRF
* wrong interface tested

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QUICK DEBUG

show ip vrf
show ip route vrf 
show run interface g0/0
ping vrf  

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MINIMAL TEMPLATE

ip vrf A
rd 1:1

interface g0/0
ip vrf forwarding A
ip address 10.0.0.1 255.255.255.0

ip route vrf A 0.0.0.0 0.0.0.0 10.0.0.254

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EXAM PATTERN

* multiple customers with same subnet
* isolation required
* routing per VRF
* combine with OSPF or firewall

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MENTAL MODEL

Each VRF = separate router inside one device
→ own interfaces
→ own routing table
→ own default route