400-007 · Question #380
Your company utilizes many different types of network transports and you want to increase the efficiency of the network. Which solution can be used to improve network efficiency over PPPoE IPsec…
The correct answer is A. PMTUD. PMTUD allows hosts to dynamically discover the maximum packet size supported along a path, preventing fragmentation caused by the overhead added by PPPoE, IPsec, and GRE encapsulation.
Question
Your company utilizes many different types of network transports and you want to increase the efficiency of the network. Which solution can be used to improve network efficiency over PPPoE IPsec, and GRE networks?
Options
- APMTUD
- BOATM
- CIRDP
- DHost Discovery Protocol
How the community answered
(53 responses)- A91% (48)
- B6% (3)
- C2% (1)
- D2% (1)
Why each option
PMTUD allows hosts to dynamically discover the maximum packet size supported along a path, preventing fragmentation caused by the overhead added by PPPoE, IPsec, and GRE encapsulation.
Path MTU Discovery (PMTUD) works by sending packets with the DF (Don't Fragment) bit set and processing ICMP 'Fragmentation Needed' messages to reduce packet size. Because PPPoE, GRE, and IPsec each add encapsulation headers that lower the effective MTU, PMTUD prevents the repeated fragmentation and reassembly that degrades throughput and increases CPU load across all three transport types.
OATM is not a recognized standard networking protocol for improving efficiency over tunneled or encapsulated transports.
IRDP (ICMP Router Discovery Protocol) allows hosts to find default gateways and has no function related to MTU optimization or tunnel efficiency.
Host Discovery Protocol is not a standard protocol for improving network efficiency over PPPoE, IPsec, or GRE networks.
Concept tested: Path MTU Discovery for tunnel encapsulation efficiency
Source: https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/25885-pmtud-ipfrag.html
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