A service provider wants to start using all of their LSPs for internal traffic and not just their MPLS VPNs. Any
solution must ensure that existing VPNs and routing policies will continue to function properly.
Which MPLS traffic engineering parameter would accomplish this task?
A.
bgp
B.
bgp-igp-both-ribs
C.
bgp-igp
D.
mpls-forwarding
Explanation:
Using LSPs for Forwarding in Virtual Private Networks
VPNs require that routes remain in the inet.3 routing table to function properly. For VPNs, configure the bgpigp-both-ribs option of the traffic-engineering statement to cause BGP and the IGPs to use LSPs for forwarding
traffic destined for egress routers.
Incorrect Answers:
C: You can configure BGP and the IGPs to use LSPs for forwarding traffic destined for egress routers by
including the bgp-igp option for the traffic-engineering statement.
https://www.juniper.net/documentation/en_US/junos15.1/topics/usage-guidelines/mpls-configuring-traffic-engineering-for-lsps.html
i would say D
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The answers is D, the question say “. Any
solution must ensure that existing VPNs and routing policies will continue to function properly.
“
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B must be the correct answer,
Traffic Engineering bgp-igp-both-ribs
This option addresses some of the limitations of traffic-engineering bgp-igp. As the names implies, with this setting the MPLS routes and egress points are installed in both the inet.0 and the inet.3 table. This allows MPLS to be used for internal forwarding, while preserving the possibility of configuring MPLS services and applications which make use of the inet.3 table.
Traffic Engineering mpls-forwarding
This mode of operation completely changes the way a router operates. From a practical point of view, this configuration will work in a way that is similar to bgp-igp-both-ribs.
However, there is a very important difference. The router will keep two set of routes: a set of routes to be used for forwarding only, which will include MPLS egress points, and a set of ordinary routes which will be computed by routing protocols, e.g. BGP, IGP, static routes and so on. As soon as the command is configured, all CLI commands that display routing information will start to display the two different route types.
This mode of operation has been designed to work around a problem encountered when configuring bgp-igp-both-ribs: the better protocol preference of MPLS-related protocols can cause MPLS routes to “overshadow” IGP and BGP routes, affecting policies and the redistribution between protocols.
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Ans is D. bgp-igp-both-ribs may cause problem for if protocol (host-bound) traffic
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When you use the bgp-igp-both-ribs statement, the routes from the inet.3 table get copied into the inet.0 table. The copied routes are LDP-signaled or RSVP-signaled, and are likely to have a lower preference than other routes in inet.0. Routes with a lower preference are more likely to be chosen as the active routes. This can be a problem because routing policies only act upon active routes. To prevent this problem, use the mpls-forwarding option instead.
https://www.juniper.net/documentation/en_US/junos/topics/usage-guidelines/mpls-configuring-traffic-engineering-for-lsps.html
mpls-forwarding—On both BGP and IGP destinations. Use ingress routes for forwarding only, not for routing.
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van29 – you say option B must be the correct answer but in your technical explanation, the “overshadowing” mean this option cannot be used.
D is the correct answer.
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D is the final asnswer.
Both option B and D serves the purpose, however, When you use the bgp-igp-both-ribs statement, the routes from the inet.3 table get copied into the inet.0 table. The copied routes are LDP-signaled or RSVP-signaled, and are likely to have a lower preference than other routes in inet.0. Routes with a lower preference are more likely to be chosen as the active routes. This can be a problem because routing policies only act upon active routes. To prevent this problem, use the mpls-forwarding option instead.
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