Refer to the exhibit. Router-WAN1 has a new connection via Gi0/0 to the ISP. Users running the web applications indicate that connectivity is unstable to the internet. What is causing the interface issue?
A.
The receive buffer is full due to a broadcast storm.
B.
Frames are discarded due to a half-duplex negotiation.
C.
Broadcast packets are rejected because ARP timeout is enabled.
D.
Small frames less than 64 bytes are rejected due to size.
The collisions are worth looking at. It implies a duplex mismatch. Although the router is full-duplex, the other side might be manually configured for a half-duplex. This causes high number of collisions.
Just FYI, broadcast storm is when when we see broadcast packet numbers above 3000. There is a 30% formula but I can't recall it.
Answer is B, but don't take my word for it, go learn something
Collisions are a strong indicator of half-duplex environment or duplex mismatch
Collisions will cause CRC errors and data corruption - another symptom of physical problem (such as duplex mismatch)
Frame errors - also a physical layer (duplex mismatch) symptom
Input errors - ALSO a physical issue indicator. correlates with duplex mismatch
We can deduce that C is not the answer because:
The ARP timeout controls how long an ARP entry remains in the ARP cache of a router or switch before it is removed or refreshed. - this has nothing to do with rejecting broadcasts
the timer is set to 4 hours
D cannot be the answer because the counter "runts" is not incremented at all.
Finally, the crowd favorite, A
110 broadcasts is pretty normal for a router, if this had been going on long enough for users to report issues, then the count would be in the tens of thousands - no indication of broadcast storm
the counter "no buffer" will increment when the number of packets dropped due to receive buffer being full. this output shows 0.
But the output shows "full duplex"! so how could it be B?
The router is set to auto negotiate the link, and if the other side is manually set to half-duplex, this can cause the router to incorrectly auto-negotiate full duplex on its side (the router is telling the other end to use full duplex, and expects it to obey, but it does not)
this would explain all of the issues caused here.
i agree that this is a difficult and tricky question, but i learned a lot digging into it, and i hope you do the same!
The correct answer is A. The receive buffer is full due to a broadcast storm.
Here's why:
In the output of the show interface command, we see 100 input errors and 260 input packets, which indicates that there may be an issue related to receiving data on the interface.
Additionally, there are 110 broadcasts and 100 collisions, which suggests that there is likely a broadcast storm or excessive broadcast traffic, overwhelming the receive buffer.
Explanation of incorrect options:
B (Half-duplex): The interface is operating in Full Duplex, so half-duplex negotiation is not the issue.
C (ARP timeout): ARP type and timeout configuration would not reject broadcast packets.
D (Small frames): There is no indication that small frames are being rejected based on size.
After looking again I realize answer is A -
B) wrong, Interface is in full duplex not half
C) wrong, arp timeout is normal
D) wrong, if this were true we'd see an increase in the 'runts' value which is 0 in this output
After looking at it again lol, I believe the answer is indeed B
I learned that between a full and hald duplex config, most of the errors will actually be present on the half duplex side of the interface, according to our output on the full duplex side we see input errors,crc,frame, and some broadcasts...this number of broadcasts is the key to indicate if we are in a broadcast storm and if we are we will receive thousands of broadcasts not a few hundred, this leads me to believe that it is indeed a duplex mismatch
there's 1 lost carrier which is mean there's an problem with physical connection i think it's B
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