What are two purposes of using IPv4 and VPNv4 address-family configurations in a Layer 3 MPLS VPN? (Choose two.)
What are two purposes of using IPv4 and VPNv4 address-family configurations in a Layer 3 MPLS VPN? (Choose two.)
IPv4 and VPNv4 address-family configurations in a Layer 3 MPLS VPN serve distinct purposes that ensure the efficient routing and management of customer traffic. First, the Route Distinguisher (RD) is prepended to the IPv4 route to make each customer's IP prefixes unique, thus avoiding conflicts when the same IPv4 addresses are used by different customers. This creates a unique VPNv4 address, which helps in the segregation of routing information. Secondly, MP-BGP (Multiprotocol BGP) is utilized to support overlapping IPv4 addresses between different customers. This capability is crucial as it allows the MPLS VPN to distinguish between identical IP addresses used in different customer networks. MP-BGP achieves this by differentiating routes with the aid of RDs, thereby ensuring that the correct route information is propagated and utilized within the network.
A: -64-bit RD prepended to IPv4 prefix to make customer routes unique = VPNv4 address https://community.cisco.com/t5/switching/i-am-not-clear-on-the-difference-between-ipv4-and-vpnv4-address/td-p/2463679 E: The VPN label is advertised to all other PE routers in an MP-BGP update. https://www.ccexpert.us/mpls/vpn-label-propagation.html
https://www.ciscolive.com/c/dam/r/ciscolive/us/docs/2019/pdf/5eU6DfQV/TECMPL-3201.pdf -vpnv4 AFI for PE to PE (label information) -All vpnv4 routes get an assigned label -vpnv4 routes are exchanged between vpnv4 peers (PEs) https://community.cisco.com/t5/mpls/mpls-vpn-inner-label/td-p/2356956 For every prefix in every VRF routing table, we make a corresponding vpnv4 prefix (RD is added to the IPv4 prefix). BGP on the egress PE then assigns a label to that vpnv4 prefix. The PE router then pushes this entry into the LFIB, with that label as incoming label (and also the label operation and next-hop). BGP advertises the vpnv4 prefix + MPLS label to all other PE routers. https://www.rfc-editor.org/rfc/rfc3107 When BGP is used to distribute a particular route, it can be also be used to distribute a Multiprotocol Label Switching (MPLS) label which is mapped to that route.
E == The VPNv4 address is used to advertise the MPLS VPN label. The VPNv4 address does NOT include ANY VPN label, also the VPNv4 address is just a name for an 48bit RD and a 32 bit prefix. The actual MP-BGP advertisement will just include the following: 1. RD (Route Distinguisher) 2. IPv4 prefix 3. Next Hop 4. VPN Label Instead of E, i personally think B is the better answer. B is still partly wrong as B states the word "prepended"==WRONG the IPv4 prefix is actually "appended" NOT "prepended". Anyway, another question of bad quality. ref: https://networklessons.com/cisco/ccnp-enarsi-300-410/mpls-layer-3-vpn-explained#RD_Route_Distinguisher
Option B can NOT be the answer because RD is 48 bit. In summary route-distinguisher: Specifies an RD, a string of 3 to 21 characters. An RD can be in one of the following formats: 16-bit AS number:32-bit user-defined number. For example, 101:3. 32-bit IP address:16-bit user-defined number. For example, 192.168.122.15:1. 32-bit AS number:16-bit user-defined number, where the AS number must be equal to or greater than 65536. For example, 65536:1.
PLEASE IGNORE THIS COMMENT, AB are correct my mistake.
You indicate the RD==48 bits. The RD is clearly 64 bits, making B the correct answer. See https://networklessons.com/cisco/ccnp-enarsi-300-410/mpls-layer-3-vpn-explained#RD_Route_Distinguisher
Read HungarianDish posted links.
OCG pag. 741-742 MPLS Layer 3 VPNv4 Address Let’s now go back to overlapping IPv4 address spaces. If all customer routes are being redistributed into MP-BGP, how does BGP handle identical network prefixes that belong to different customers? It uses a route distinguisher (RD) to expand the customer’s IP prefix so that it includes a unique value that distinguishes it from the other identical prefixes. The RD is generated and used by the PE routers on a per-customer VRF instance basis, and to keep things simple, the RD is used regardless of whether there are overlapping address spaces. So, the RD is used all the time. The unique 64-bit RD is prepended to the 32-bit customer prefix (IPv4 route) to create a 96-bit unique prefix called a VPNv4 address, as shown in Figure 18-14. This VPNv4 address is exchanged by the MP-IBGP neighboring routers.
VPNv4 is known as an RD. They are not used to advertise the MPLS VPN Label
Page 742 300-410 Official Cert Guide; RD (8-bytes) & IPv4 Address (4-Bytes) creates a 96-bit unique prefix called VPNv4 address.
Why C is wrong?
I think because it is VRF not MPLS allowing overlapping
Yeah, like in the context of what we know mpls l3vpn to be, C is right, but its not in the context of the question. I had to re read C a couple times to see that.
A and B.
A n B the give answer is correct, plese check anwser Rob_CCNP000 . I have the book. Its true
A & B are correct
I go for A and B to, answer E for sure is not true, the protocol used in MPLS for propagating the labels in mpls is the LDP protocol, every label then is attached to an vpnv4 prefix so that the router will use the LFIB to send traffic to the correct destination.
A. Is clear true because the RD is prepended. B. On the first view it seems to be true, BUT the wording is tricky. A VPNv4 prefix consits of the 64-bit RD and the 32-bit IPv4 prefix making it a 96-bit prefix. C. It is true. D. non-sense E. non-sense
Sry my fault. Ingore it.
Something has changed in the order of answers? For example HungarianDish explained why BE the right choice, while voted AE. B: The VPNv4 address consists of a 64-bit route distinguisher that is prepended to the IPv4 prefix E: The VPNv4 address is used to advertise the MPLS VPN label.
Answer A wrong, because RD is prepended to the IPv4 prefix, not to the IPv4 route.
AB E is wrong because MP-BGP (not VPNv4) is used to advertise MPLS VPN labels
2 answers saying the same thing, no make sense.
https://community.cisco.com/t5/switching/i-am-not-clear-on-the-difference-between-ipv4-and-vpnv4-address/td-p/2463679 The VPNv4 address family is used to advertise VPNv4 NLRI. VPNv4 address consists of 64-bit Route Distinguisher (RD) prepended to IPv4 prefix. This is to make routes unique that are in different VRFs.
So the answers are A & E?
The given answer is correct