Question about Vrf-Lite

With VRF lite, are Route distinguishers necessary? I see them in a lot of peoples labs, and just don't see the point to it. I thought they are only required for MP-BGP / MPLS VPNs, since VPN-IPv4 addresses are a type of BGP address.

Comments

  • dtlokeedtlokee Posts: 2,381Member
    Are they really needed, probably not because the don't need to carry tags between routers only internally but some unique ID is required. I don't think I have seen a configuration example that does not have the RD set. I use them whenever I configure VRF Lite. It's possible that it will work but it may also cause unpredictable results.
    The only easy day was yesterday!
  • yuriz43yuriz43 Posts: 121Member
    Well, I had to lab this up! As expected, RD is not required for VRF-Lite.


    Picture of lab
    GNS3 Project File
    Router configs

    R0#show ip vrf
    Name Default RD Interfaces
    test1 <not set> Lo1
    Fa0/0.1
    test2 <not set> Lo2
    Fa0/0.2
    test3 <not set> Lo3
    Fa0/0.3

    R0#show ip int brief
    Interface IP-Address OK? Method Status Protocol
    FastEthernet0/0 unassigned YES unset up up
    FastEthernet0/0.1 172.16.1.1 YES manual up up
    FastEthernet0/0.2 172.16.1.1 YES manual up up
    FastEthernet0/0.3 172.16.1.1 YES manual up up
    Loopback1 10.0.0.1 YES manual up up
    Loopback2 10.0.0.2 YES manual up up
    Loopback3 10.0.0.3 YES manual up up




    R0 is advertising each loopback via multiple OSPF instances (vrf test1, test2, and test3). Lets see how the routing looks on R1 now:



    R1#show ip route vrf test1

    172.16.0.0/24 is subnetted, 1 subnets
    C 172.16.1.0 is directly connected, FastEthernet0/0.1
    10.0.0.0/32 is subnetted, 1 subnets
    O 10.0.0.1 [110/2] via 172.16.1.1, 00:11:33, FastEthernet0/0.1

    R1#show ip route vrf test2

    172.16.0.0/24 is subnetted, 1 subnets
    C 172.16.1.0 is directly connected, FastEthernet0/0.2
    10.0.0.0/32 is subnetted, 1 subnets
    O 10.0.0.2 [110/2] via 172.16.1.1, 00:05:37, FastEthernet0/0.2

    R1#show ip route vrf test3

    172.16.0.0/24 is subnetted, 1 subnets
    C 172.16.1.0 is directly connected, FastEthernet0/0.3
    10.0.0.0/32 is subnetted, 1 subnets
    O 10.0.0.3 [110/2] via 172.16.1.1, 00:05:26, FastEthernet0/0.3




    I wouldn't be able to sleep without getting to the bottom of this. Any ways, I need to get back to the ISCW, I am getting side tracked again!! ( happens a lot with me because there are just so mainly details with each bit of technology you study )
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