DIAG

HSRP:
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Cause: CE1
Resolution: increase CE1's hsrp priority
Wireshark: Select the first HSRP negotiation packet

CE1 is HSRP Standby with nd-preference High
CE2 is HRSP Active with nd-preference Low


MCAST:
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#1 root-cause of the issue?
 "no route to reach RP from R3"

 #2 what is the info needed from L1 engineeer to confirm the root-cause?
 "why is '10.1.4.1' not found in RIB table in R3"

 #3 quick Fix
 "ip route 10.1.4.1 255.255.255.255 10.0.0.17"


Port-Security:
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Part - 1.1 : Which switch has the problem?
Answer : Select device SW3
Part - 1.2 : Which command to use for identifying the problem?
Answer : Show ip int brief

Part 2.1 : Which Device has the problem?
Answers : Select device Host-1
Part 2.2 : Which command to use for identifying the problem?
Answers : MAC address of interface Ex/x

VTP:
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Part - 1.1 : Which switch has the problem?
Answer : Select device SW3
Part - 1.2 : Which command to use for identifying the problem?
Answer : Show vtp status

Part 2.1 : Which Device has the problem?
Answers : Select device Sw3
Part 2.2 : Which command to use for identifying the problem?
Answers : Show vtp password(ask for vtp password)

DMVPN-1:
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*In Logs you can see " Midchain parent maintenance for IP Midchain out of Tunnel0, addr X.X.X.X - looped chain attempting to stack" (X.X.X.X address is R15's NBMA address)

Part 3.1 : Which Device we will select?
R15

Part 3.2 : Which command to use for identifying the problem?
Device: Redistribute connected
Command Line: exclude (e0/0) nbma from eigrp

DMVPN-2:
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On Site A, the R16 interface E1/0 is configured with /29 network. It should be configured with /30 mask

Part 3.1 : Which Device has the problem?
Select Device: R16

Part 3.2 : Which command to use for identifying the problem & What is the resolution?
Device: Show ip int brief
Command Line: Increase the subnet mask length to /30

URPF:
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When a packet is received at the interface where Unicast RPF and ACLs have been configured, the following actions occur:

Step 1 Input ACLs configured on the inbound interface are checked.

Step 2 Unicast RPF checks to see if the packet has arrived on the best return path to the source, which it does by doing a reverse lookup in the FIB table.

Step 3 CEF table (FIB) lookup is carried out for packet forwarding.

Step 4 Output ACLs are checked on the outbound interface.

Step 5 The packet is forwarded.