A company plans to use BFD between its routers to detect a connectivity problem inside the switched network. An IPS is transparently installed between the switches. Which packets should the IPS forward for BFD to work under all circumstances?
A.
Fragmented packet with the do-not-fragment bit set
B.
IP packets with broadcast IP source addresses
C.
IP packets with the multicast IP source address
D.
IP packet with the multicast IP destination address
E.
IP packets with identical source and destination IP addresses
F.
IP packets with the destination IP address 0.0.0.0.
BFD (Bidirectional Forwarding Detection) operates by exchanging control packets between peers, typically using UDP encapsulation. In single-hop deployments, BFD sessions are often established using:
Source IP = destination IP = local interface IP (identical source and destination addresses), especially in certain implementations like Cisco single-hop BFD.
This allows rapid fault detection without routing dependency.
The IPS must permit these packets to avoid disrupting BFD functionality.
Why other options are incorrect:
A: Fragmentation is irrelevant to BFD.
B, C, D, F: BFD does not use broadcast, multicast, or 0.0.0.0 addresses.
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