350-401 · Question #257
Refer to the exhibit. interface Ethernet 0/0 ip policy routemap PBR routemap PBR match ip address 144 set ip nexthop 172.16.12.5 set ip nexthop recursive 192.168.3.2 Which statement describes how a ro
The correct answer is A. It routes the packet using the default routing table.. When Policy-Based Routing (PBR) next-hops become unreachable, the router reverts to its normal forwarding behavior, using the standard IP routing table to route the packet.
Question
Options
- AIt routes the packet using the default routing table.
- BIt routes the packet into a loop and drops it when the TTL reaches zero.
- CIt drops the packet immediately.
- DIt sends an ICMP source quench message.
How the community answered
(36 responses)- A64% (23)
- B8% (3)
- C6% (2)
- D22% (8)
Why each option
When Policy-Based Routing (PBR) next-hops become unreachable, the router reverts to its normal forwarding behavior, using the standard IP routing table to route the packet.
Cisco PBR configuration includes a fallback mechanism for `set ip nexthop`. If all specified next-hops in the PBR policy are unreachable or cease to be valid, the router defaults to processing the packet based on its destination IP address using the regular IP routing table, ensuring continued connectivity.
PBR failing to find a next-hop does not inherently lead to routing loops or dropping packets due to TTL expiry; it means the PBR rule is not applied, and normal routing takes over.
The router does not immediately drop the packet if PBR next-hops are unreachable; instead, it attempts to route the packet using the standard routing table.
ICMP source quench messages are used for congestion control, not as a response when PBR next-hops become unreachable.
Concept tested: Policy-Based Routing (PBR) fallback
Source: https://www.cisco.com/c/en/us/td/docs/ios/12_2/qos/configuration/guide/qcfipbr.html
Topics
Community Discussion
No community discussion yet for this question.