Exam 350-501 topic 1 question 348 discussion

Answer: BD -1) R2 is sending hello with "1699 bytes," whereas the maximum MTU is "1500 bytes.". The following link is explained very well. -2) If we change the MTU to "1500 bytes" on the R2 interface, then it will send hello with "1499 bytes," and it will build the neighborship if the link is not over MPLS. -3) With Hello padding disabled on the interface Serial 2/0, the size of the Hello packet to the minimum. -4) Thus, if you only disable the IS-IS Hello padding, it is not enough to bring up the IS-IS adjacency. The MTU must be low enough so that the MTU-sized IS-IS Hello packets are sent and received properly by the routers on either side of the link.

Sorry guys but it seems like answer is B, D Adjust MTU Disable Hello padding so that ISIS does not detect MTU mismatches, as there wont be any need to

I will go for A and E https://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system-to-intermediate-system-is-is/119399-technote-isis-00.html#:~:text=Note%3A%20Cisco%20recommends%20that%20you%20do%20not%20disable%20the%20IS%2DIS%20Hello%20padding%20in%20order%20to%20ensure%20that%20two%20routers%20form%20an%20IS%2DIS%20adjacency%20on%20a%20link%20that%20has%20mismatched%20MTU%20values%20on%20either%20side.

https://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system-to-intermediate-system-is-is/119399-technote-isis-00.html The MTU on the serial interfaces for the routers R1 and R2 are the default 1,500 bytes. The IS-IS adjacency fails because the IS-IS Hello packets are 1,499 bytes in size. The MPLS network only allows 1,500-byte packets, minus eight bytes (two MPLS labels for the MPLS service), which equals 1,492 bytes (the packet size that is allowed to pass through). For transport of L2 over MPLS, the size of the L2 header must be subtracted from the 1,492 bytes that result as well.