Analyzing the Exhibit

The diagram represents BGP peering between:

AS 65512 (Enterprise Network)

AS 65511 (ISP-A)

R3 and R4 are peering with ISP-A using EBGP .

R1, R2, R3, and R4 are peering within AS 65512 using IBGP .

Understanding BGP Route Behavior

Option A: " By default, the next-hop value for these routes is not changed by ISP-A before being sent to R3. " ❌

Incorrect!

EBGP behavior: When a BGP route is advertised via EBGP , the next-hop IP is changed to the router ' s own IP by default .

Since ISP-A is advertising routes via EBGP to R3, the next-hop is changed to ISP-A’s IP .

Thus, this statement is incorrect.

Option B: " The BGP local-preference value that is used by ISP-A is not advertised to R3. " ✅

Correct!

BGP Local Preference (LOCAL_PREF) is an IBGP-only attribute .

Local Preference is NOT shared over EBGP because it is used within an AS to influence route selection.

ISP-A will not send LOCAL_PREF to R3 , as R3 is in a different AS.

Thus, this statement is correct.

Option C: " All BGP attribute values must be removed before receiving the routes. " ❌

Incorrect!

BGP does not remove all attributes when advertising routes. Some attributes are modified (e.g., next-hop, AS-PATH), but others (like MED, community) may be preserved.

Thus, this statement is incorrect.

Option D: " The next-hop value for these routes is changed by ISP-A before being sent to R3. " ✅

Correct!

As per default EBGP behavior , the next-hop is changed when a route is advertised to an EBGP peer.

This means ISP-A changes the next-hop to its own IP before sending it to R3.

Thus, this statement is correct.

Final Answer:

✅ B. The BGP local-preference value that is used by ISP-A is not advertised to R3.

✅ D. The next-hop value for these routes is changed by ISP-A before being sent to R3.

Verification from Juniper Documentation:

Juniper BGP Configuration Guide confirms that LOCAL_PREF is not advertised over EBGP .

RFC 4271 (BGP-4) specifies that next-hop is changed by default when advertising routes via EBGP .

Understanding the Exhibit and the Problem Statement

The diagram shows a Layer 3 VPN (L3VPN) setup where multiple customers ( Customer A, B, and C ) are connected across a service provider network using PE (Provider Edge) routers .

PE1 and PE2 exchange VPN routes for all customers using BGP/MPLS Layer 3 VPN (L3VPN) routing .

The question asks how to verify if PE2 is receiving VPN routes for Customer C .

Evaluating the Answer Choices

✅ B. show route table bgp.l3vpn.0 (Correct Answer)

Why?

This command shows all VPN routes stored in the BGP Layer 3 VPN table (bgp.l3vpn.0) .

Since PE routers exchange VPN routes using MP-BGP , this table contains the VPN-IPv4 or VPN-IPv6 routes for all customers.

If PE2 is receiving routes from PE1 for Customer C , they will appear in bgp.l3vpn.0.

❌ A. show route table inet.0 (Incorrect)

Why?

The inet.0 table contains global unicast routes for the service provider ' s network.

VPN routes do not appear here because they are stored in VRF-specific tables.

This command won’t help verify VPN route exchange between PE1 and PE2.

❌ C. show route table customer-c.inet.0 (Incorrect)

Why?

The table customer-c.inet.0 represents the VRF routing table for Customer C on the local PE .

It only shows locally installed routes for Customer C but does not confirm if PE2 is receiving routes from PE1 .

This command is useful to check local VPN routing but not BGP route propagation .

❌ D. show route summary (Incorrect)

Why?

This command only provides a summary of route counts per protocol (BGP, OSPF, etc.).

It does not display specific VPN routes .

It is useful for general troubleshooting but doesn’t confirm VPN route receipt .

Final Answer: ✅ show route table bgp.l3vpn.0 (Option B)

Official Juniper Documentation Reference

Junos MPLS VPNs Configuration Guide ???? Juniper Documentation

" The show route table bgp.l3vpn.0 command displays all VPN-IPv4 routes learned via MP-BGP for Layer 3 VPNs. "

The customer interface in an LDP-signaled pseudowire is the interface on the PE router that connects to the CE device. An LDP-signaled pseudowire is a type of Layer 2 circuit that uses LDP to establish a point-to-point connection between two PE routers over an MPLS network. The customer interface can have different encapsulation types depending on the type of traffic that is carried over the pseudowire. The encapsulation types are ethernet-ccc, vlan-ccc, extended-vlan-ccc, atm-ccc, frame-relay-ccc, ppp-ccc, cisco-hdlc-ccc, and tcc-ccc. Depending on the encapsulation type, the customer interface can accept or reject tagged or untagged frames in the data plane, and include or exclude VLAN tags in the control plane LDP advertisement. The following table summarizes the behavior of different encapsulation types:

To create a summary route for IS-IS, you need to configure a policy statement that matches the prefixes to be summarized and sets the next-hop to discard. You also need to configure a summary-address statement under the IS-IS protocol hierarchy that references the policy statement. In this case, the policy statement leak-v6 is trying to match the prefix 2001:db9:a:fa00::/61 exactly, but this prefix is not advertised by any router in the network. Therefore, no summary route is created. To fix this, you need to delete the longer keyword from the route-filter term and change the prefix length to /61 exact. This will match any prefix that falls within the /61 range. You also need to delete the export statement under protocols isis, because this will export all routes that match the policy statement to other IS-IS routers, which is not desired for a summary route.

Intermediate System to Intermediate System ( IS-IS ) is a link-state routing protocol that supports Level 1 (L1), Level 2 (L2), or both (L1/L2) operations . The way IS-IS sends Hello (IIH) packets depends on whether the interface is point-to-point (P2P) or broadcast (LAN) .

Evaluating the Answer Choices

✅ Option A: " If a point-to-point interface is in both L1 and L2, separate hello messages are sent for each level. "

Incorrect!

On point-to-point (P2P) interfaces , only one combined Hello message is sent for both L1 and L2.

IS-IS P2P Hellos include both Level 1 and Level 2 TLVs in the same message .

VPLS is a technology that provides Layer 2 VPN services over an MPLS network. VPLS uses BGP as its control protocol to exchange VPN membership information between PE routers. The route target is a BGP extended community attribute that identifies which VPN a route belongs to. The route target must match on PE routers that participate in the same VPLS instance, otherwise they will not accept or advertise routes for that VPLS.

A sham link is a logical link between two PE routers that belong to the same OSPF area but are connected through an L3VPN. A sham link makes the PE routers appear as if they are directly connected, and prevents OSPF from preferring an intra-area back door link over the VPN backbone.  To create a sham link, you need to configure the local and remote addresses of the PE routers under the [edit protocols ospf area area-id] hierarchy level 1 .

https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/topic-map/configuring-ospfv2-sham-links.html