
question into routing in ccnp r&s to mr/keith bogart
in CCNP General
hello my sir
iam into your lecture :-
33 - Basic Switch Configuration & Verification Part 3
as you say into this example that R2 will send broadcast arp msg to r1
to know his own mac address
but into brodcast it`s FFFF.FFFF.FFFF
NOW AS YOU SEE INTO THIS EXAMPLE WHY R2 SEND 0000.0000.0000
(AS YOU SEE INTO RED
MARK) NOT SEND IT FFFF.FFFF.FFFF? WHY HE`S DOING THAT?
ALSO INTO GRATITUOUS ARP PROTOCOL , YOU SAY THAT
R2 SEND REPLY BROADCAST
MESSAG WITHOUT ANY REQ ? WHY R2 DO THAT?
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answer from mr/keith bogart
Hi Mohammed,
Your question is a great example of why I always recommend that people obtain actual packet captures (Sniffer traces) to really understand how protocols work.
In the output of “debug arp” that you’ve provided, I can understand how you’d mistakenly assume that the 0000.0000.0000 represents the destination MAC address of the ARP Request…but it does not. That part of the output is actually showing you a field within the ARP packet called the, “Target MAC Address” field.
See below from an ARP Request packet capture:

Comments
This is the second time I see a post that already has an answer from Keith Bogart, haha.
Hope this helps!
Timothy Q. Manito
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this message to man or woman that`s called rriker
i never send any private emails to anyone except for ttwo persons
mr / brian mcgahan
mr / keith bogart
and only one who reply for me is mr / keith bogart
why you lying to me and say what did not happen
be obvious don`t be Liar