300-510 Question #258: Real Exam Question with Answer & Explanation

Question

SIMULATION Guidelines This is a lab item in which tasks will be performed on virtual devices. - Refer to the Tasks tab to view the tasks for this lab item. - Refer to the Topology tab to access the device console(s) and perform the tasks. - Console access is available for all required devices by clicking the device icon or using the tab(s) above the console window. - All necessary preconfigurations have been applied. - Do not change the enable password or hostname for any device. - Save your configurations to NVRAM before moving to the next item. - Click Next at the bottom of the screen to submit this lab and move to the next question. - When Next is clicked, the lab closes and cannot be reopened. Topology Tasks Troubleshoot and configure BGP according to the topology to achieve these goals: 1. R1 and R3 establishes IBGP connectivity using Loopback addresses. The updates should come from Loopback0. 2. R3 should be able to ping loopback0 interface of R2. These changes must be accomplished through BGP. 3. R1 advertises only the summary route of 172.16.100.0/22 to R2 and R3. Answer: Step 1: R1 and R3 IBGP Connectivity Using Loopback0 To establish IBGP between R1 and R3 using their Loopback0 interfaces and ensure updates originate from Loopback0, configure the following: On R1: router bgp 100 neighbor 10.3.3.3 remote-as 100 neighbor 10.3.3.3 update-source Loopback0 On R3: router bgp 100 neighbor 10.1.1.1 remote-as 100 neighbor 10.1.1.1 update-source Loopback0 ensures that the BGP updates are sourced from neighbor update-source Loopback0 Loopback0. Verify the BGP peering: show ip bgp summary Step 2: R3 Can Ping R2 Loopback0 (10.2.2.2/32) To allow R3 to reach R2's Loopback0, configure R1 to redistribute the route from EBGP to IBGP. Ensure next-hop resolution works correctly: On R1: router bgp 100 neighbor 10.3.3.3 next-hop-self next-hop-self: This changes the next-hop IP to R1's IP when advertising routes to R3. This ensures R3 can resolve the next-hop for R2's loopback. Step 3: R1 Advertises Only Summary Route (172.16.100.0/22) To advertise only the summary route 172.16.100.0/22 to both R2 and R3: On R1: router bgp 100 network 172.16.100.0 mask 255.255.252.0 aggregate-address 172.16.100.0 255.255.252.0 summary-only aggregate-address 172.16.100.0 255.255.252.0 summary-only advertises the summary route and suppresses more specific routes. Verification Commands: Verify IBGP Peering: show ip bgp summary Verify BGP Advertisements: show ip bgp Verify R3 Reachability to R2's Loopback: ping 10.2.2.2 source Loopback0 Verify the Summary Route Advertisement on R2 and R3: show ip bgp IBGP Peering: Use Loopback0 and configure update-source. Next-Hop Resolution: ensures reachability for EBGP routes. next-hop-self Summary Route: Use aggregate-address with summary-only to advertise a summary route.

Options

• AIt reflects the route reflector cluster ID within the confederation.
• BIt carries the AS number within the confederation's local autonomous system.
• CIt advertises routes outside of the confederation's autonomous system.
• DIt identifies the autonomous system that belongs to the confederation.