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
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
In my opinion I think that E is not right because who advertises the VPN label is the NLRI sended by BGP that contains RD, IPv4 prefix, Next-hop and VPN label.
A and B is more accurate.
answer is A and E I explain why now:
A. RD is prepended to the IPv4 route to make it unique. (yes this is a PURPOSE)
B. The VPNv4 address consists of a 64-bit route distinguisher that is prepended to the IPv4 prefix. (This is true but not a PURPOSE of VPNv4)
C. MP-BGP is used to allow overlapping IPv4 addresses between customers to advertise through the network. (No this is VRF's)
D. The IPv4 address is needed to tag the MPLS label.
E. The VPNv4 address is used to advertise the MPLS VPN label. (The label this is referring to is the inner VPN label, not the MPLS label - VPNv4 is a multiprotocol BGP addition, that includes extended family functionality. When under 'address-family vpn4' configuration in BGP, we send-community extended. This propagates VPNv4 reachability through the VPN label. This is the purpose of VPNv4. Answer is A and E.
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.
A. RD is prepended to the IPv4 route to make it unique.
The Route Distinguisher (RD) is used to make IPv4 routes unique across different VPNs by prepending it to the IPv4 prefix.
C. MP-BGP is used to allow overlapping IPv4 addresses between customers to advertise through the network.
Multiprotocol BGP (MP-BGP) allows the advertisement of overlapping IPv4 addresses between different customers by using VPNv4 addresses, which include the RD.
The correct answers are:
B. The VPNv4 address consists of a 64-bit route distinguisher that is prepended to the IPv4 prefix.
C. MP-BGP is used to allow overlapping IPv4 addresses between customers to advertise through the network.
Here's a breakdown of why:
VPNv4 Address: In a Layer 3 MPLS VPN, the VPNv4 address is a combination of a 64-bit route distinguisher (RD) and the IPv4 prefix. The RD uniquely identifies the VPN, allowing multiple customers to use overlapping IPv4 addresses within the network.
MP-BGP: Multiprotocol BGP (MP-BGP) is used to advertise both IPv4 and VPNv4 routes within the MPLS VPN.
This allows different customers to use overlapping IPv4 addresses without causing routing conflicts
My vote goes towards A and B, but honestly, it might be A and E, or B and E. All I am sure of is that C and D are incorrect.
You know a question is poorly written when people can't even agree on the answer while having access to Google and all the time in the world to figure it out...
answer is A and E I explain why now:
A. RD is prepended to the IPv4 route to make it unique. (yes this is a PURPOSE)
B. The VPNv4 address consists of a 64-bit route distinguisher that is prepended to the IPv4 prefix. (This is true but not a PURPOSE of VPNv4)
C. MP-BGP is used to allow overlapping IPv4 addresses between customers to advertise through the network. (No this is VRF's)
D. The IPv4 address is needed to tag the MPLS label.
E. The VPNv4 address is used to advertise the MPLS VPN label. (The label this is referring to is the inner VPN label, not the MPLS label - VPNv4 is a multiprotocol BGP addition, that includes extended family functionality. When under 'address-family vpn4' configuration in BGP, we send-community extended. This propagates VPNv4 reachability through the VPN label. This is the purpose of VPNv4. Answer is A and E.
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
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.
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
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.
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.
A voting comment increases the vote count for the chosen answer by one.
Upvoting a comment with a selected answer will also increase the vote count towards that answer by one.
So if you see a comment that you already agree with, you can upvote it instead of posting a new comment.
HungarianDish_111
Highly Voted 1 year, 7 months agoPietjeplukgeluk
1 year, 1 month agoVanrolo
4 weeks agobk989
5 months, 1 week agoHungarianDish_111
1 year, 7 months agoDenskyDen
Highly Voted 1 year, 7 months agotubirubs
Most Recent 3 months, 3 weeks agotubirubs
3 months, 3 weeks agogalimuna
3 months, 4 weeks agobf10690
5 months, 1 week agobk989
5 months, 1 week ago[Removed]
6 months ago[Removed]
6 months ago[Removed]
6 months agoXBfoundX
7 months, 1 week agoTedmus
1 year, 1 month agoTedmus
1 year, 1 month agolouisvuitton12
1 year, 2 months agolouisvuitton12
1 year, 2 months agoPietjeplukgeluk
1 year, 1 month agojansan55
1 year, 4 months agojansan55
1 year, 4 months agoColmenarez
1 year, 4 months agoguy276465281819372
1 year, 5 months agoJieW
1 year, 5 months agointeldarvid
1 year, 5 months ago