3.6.a Describe packet types

wanted to make room for hello’s, dbd’s, lsr, lsu, lsa (acknowledgment



arrow rightospf hello

arrow up

notice the bottom part of wireshark that’s highlighted. if you can interpret hex you’ll see the fields in the body correspond to the raw data below, ie, the mask field is and is represented in hex by ff ff ff 00. the hello interval is ten seconds, or 0a, etc.


ospf dbdospf ws dbd

note mtu is highlighted.

remember with hex

multiples of 16 place|the 16’s place|units place

since there are 3 places you have left to right (the fourth on the left = 0):

05 dc

0 + 5* 256 +  d=13 *16 + c = 12

total 1500

each corresponding place holder is multiplied by 16.

so the fourth place holder is 4096 or 16 times 256


more than that, get a calculator…


lsr internet diaospf lsr

note here that three lsa types are represented, 1) router 3) summary and 4) asbr summary


this is a response to an LSR. it may contain multiple LSA’s as in the output.


LSA (acknowledgment)

multiple lsa’s may be acknowledged witjh a single ack

ospf lsa ack