300-410 · Question #41
300-410 Question #41: Real Exam Question with Answer & Explanation
The correct answer is D: access-list 1 permit 192.168.130.0 0.0.0.255 ! interface Gi0/1 ip policy route-map test ! route-map test permit 10 match ip address 1 set ip next-hop 172.20.40.1. This configuration uses policy-based routing (PBR) to redirect traffic originating from the 192.168.130.0/24 network that enters R1 on interface Gi0/1, explicitly directing it to a next-hop IP address of 172.20.40.1 to achieve forwarding towards R2.
Question
Refer to the exhibit. The exhibit shows Router R1 connected to the 192.168.130.0/24 network. R1 has interfaces Gi0/1 (IP 172.20.40.3/30) and Gi0/2 (IP 172.20.20.3/30). R2 has interface Gi0/1 (IP 172.20.20.4/30) and is connected to R1's Gi0/2. R3 has interface Gi0/1 (IP 172.20.40.4/30) and is connected to R1's Gi0/1. Which configuration configures a policy on R1 to forward any traffic that is sourced from the 192.168.130.0/24 network to R2?
Options
- Aaccess-list 1 permit 192.168.130.0 0.0.0.255 ! interface Gi0/2 ip policy route-map test ! route-map test permit 10 match ip address 1 set ip next-hop 172.20.20.2
- Baccess-list 1 permit 192.168.130.0 0.0.0.255 ! interface Gi0/1 ip policy route-map test ! route-map test permit 10 match ip address 1 set ip next-hop 172.20.40.2
- Caccess-list 1 permit 192.168.130.0 0.0.0.255 ! interface Gi0/2 ip policy route-map test ! route-map test permit 10 match ip address 1 set ip next-hop 172.20.20.1
- Daccess-list 1 permit 192.168.130.0 0.0.0.255 ! interface Gi0/1 ip policy route-map test ! route-map test permit 10 match ip address 1 set ip next-hop 172.20.40.1
Explanation
This configuration uses policy-based routing (PBR) to redirect traffic originating from the 192.168.130.0/24 network that enters R1 on interface Gi0/1, explicitly directing it to a next-hop IP address of 172.20.40.1 to achieve forwarding towards R2.
Common mistakes.
- A. The
set ip next-hop 172.20.20.2is not the correct next-hop for R2's directly connected interface (172.20.20.4) and applying the policy on Gi0/2 assumes traffic from 192.168.130.0/24 enters R1 on that interface, which is less commonly implied for a 'LAN' source. - B. While applying the policy on Gi0/1 might be correct if 192.168.130.0/24 traffic enters there, the
set ip next-hop 172.20.40.2is an IP on the R1-R3 segment and not the stated R2 interface (172.20.20.4), thus it does not directly fulfill the requirement of forwarding to R2. - C. Applying the policy on Gi0/2 is likely incorrect for ingress traffic from the source network, and the
set ip next-hop 172.20.20.1is not the correct next-hop for R2's directly connected interface (172.20.20.4).
Concept tested. Policy-based routing configuration (PBR)
Reference. https://www.cisco.com/c/en/us/td/docs/ios/12_2/qos/configuration/guide/fqos_c/qcfpolbr.html
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