mpls vpn query

marcusaureliusbrutusmarcusaureliusbrutus MemberMember Posts: 73 ■■□□□□□□□□
Hi guys,

I need help.

I have been studying MPLS but still find several concepts confusing.

I tried setup a lab work for this but the result failed.

I have several question which i hope you could clarify.

1. For MPLS/VPN to work, meaning that when i do a 'show ip vrf', should the same route appear in the bgp table when i do a show ip bgp or show ip route? The reason i am asking is because of the command example below.

address-family ipv4 vrf siteA
neighbor 1.1.1.2 remote-as 200
neighbor 1.1.1.2 activate
redistribute connected

Redistribution occurs on the ipv4 vrf. So whenever i check the routing table, no entries are advertised there.

2. Whenever i apply 'ip vrf forwarding' to an interface, that interface becomes unpingable even after i have given it an IP address. Is this normal?
3. Is ISIS necessary for MPLS/VPN? Can't i just use bgp all through out?
4. Config examples show mpls applied to a loopback interface;

int l1
ip vrf forwarding siteA
ip add 2.2.2.2 255.255.255.0

However, cisco docs say that mpls has to be applied on the interface connected to another mpls router. Which is correct?

Thanks in advance for your help.

Comments

  • wireratwirerat Senior Member Member Posts: 251
    2. Whenever i apply 'ip vrf forwarding' to an interface, that interface becomes unpingable even after i have given it an IP address. Is this normal?
    3. Is ISIS necessary for MPLS/VPN? Can't i just use bgp all through out?

    2. Are you doing a 'ping vrf <vrf name> <interface ip address> ?
    3. BGP can be run throughout. ISIS is not necessary.

    I wish I could answer your other questions but I only know a little about MPLS VPNs because of work.
  • networker050184networker050184 Went to the dark side.... Mod Posts: 11,962 Mod
    No offense, but I think you need to go back and reread the book (again if you already have). It doesn't seem like you are understanding this at all. I don't think anyone is going to write a novel here to explain it from the ground up.
    An expert is a man who has made all the mistakes which can be made.
  • ColbyGColbyG Senior Member Member Posts: 1,264
    1. For MPLS/VPN to work, meaning that when i do a 'show ip vrf', should the same route appear in the bgp table when i do a show ip bgp or show ip route? The reason i am asking is because of the command example below.

    2. Whenever i apply 'ip vrf forwarding' to an interface, that interface becomes unpingable even after i have given it an IP address. Is this normal?
    3. Is ISIS necessary for MPLS/VPN? Can't i just use bgp all through out?
    4. Config examples show mpls applied to a loopback interface;

    int l1
    ip vrf forwarding siteA
    ip add 2.2.2.2 255.255.255.0

    1. No, you should not have the same routes in your VRF and global table by default.
    2. Yes it's normal, you have multiple routing tables now, which are all separate from each other. You can use the ping vrf <vrf> command.
    3. IS-IS is not necessary for MPLS VPNs.
    4. That loopback is part of VRF siteA. I don't understand the question.

    Like networker said, go back and read or watch videos. You need to grasp the fundamentals better. MPLS is a very deep topic.
  • yuriz43yuriz43 Senior Member Member Posts: 121
    You can use any IGP to exchange routes with a CE router.
    It looks like you want to use BGP with your CE.

    If you want a running example, take a look at this. ( I'm using OSPF for exchanging internal routes, and for exchanging routes with CE devices. )

    Picture of Topology
    GNS3 Project File
    Router configuration files
  • abhustlerabhustler Member Member Posts: 49 ■■□□□□□□□□
    I agree with wirerat. You need to specify the vrf when you ping an internal vrf. If you do a sh ip route vrf siteA you will see that the connected routes listed are only the interfaces with the vrf forwarding command on them. In contrast if you do just a sh ip route you will no longer see the vrf interface listed as connected so it wont know how to reach that ip address.
    A master at anything was once a beginner
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