This is possibly one of those situations with just a poorly worded question. Now, to nit-pick at the wording.. "The following IP *ADDRESSES*" -- Addresses, not networks, but ADDRESSES.. Now, is this VLSM summarization, in which case "no bits in the 3rd octet" without doing 2 summaries (50% savings on the routing table traffic, but why when you could 172.16/16 for 75% savings). The other possibility, is (I do this occassionally on firewall rules setups) summarizing for an access list. In other words, "What is an IP/mask combination that will match those 4 addresses." The answer would be : 172.16.0.0 = 172.16.00000000.0 172.16.64.0 = 172.16.01000000.0 172.16.128.0 = 172.16.10000000.0 172.16.192.0 = 172.16.11000000.0 Remember that the mask in an access-list etc, does NOT need to be contiguous bits.. therefor : 172.16.0.0 0.0.192.255 (172.16.xx000000.x) works fine for those specific addresses (and added feature, doesn't include anything else). Just another point of view to look at this question from. Remember that while writing a Cisco exam, or out in the real world, ASSUME NOTHING. If it does not mention VLSM, don't assume they are talking about VLSM. If possible, check on what the exam says is the "correct" answer, and try to reverse-engineer their thinking to see what topic they are covering. Also, check the erratta for the exam to make sure you are looking at a "correct" answer. Regards, Trevor Corness, CCNA MCSE MCP+I Network Systems Engineer, DataCom BMS Communications Ltd. http://www.bmscom.com "John lay" <[EMAIL PROTECTED]> wrote in message > Guys, > > While studying for the CCDA, I found the following question in one of the > exam preparation sites. > > The following IP addresses can be summaried by which bit of the 3rd octet > 172.16.0.0, 172.16.64.0, 172.16.128.0, 172.16.192.0 ---> 1st bit, first 2 > bit, first 4 bit, last 6 bit > > I don't think that the following addresses could be summarized on any bit of > the 3rd octet. > If you have a look to the 3rd octet > 172.16.0.0 ---> 172.16.00000000.0 > 172.16.64.0 ---> 172.16.01000000.0 > 172.16.128.0---> 172.16.10000000.0 > 172.16.192.0---> 172.16.11000000.0 > > Could someone verify this with me guys ? > Thanks a lot
BEGIN:VCARD VERSION:2.1 N:Corness;Trevor FN:Trevor Corness ORG:BMS Communications;DataCom TITLE:Network Systems Engineer TEL;PAGER;VOICE:604-631-7867 ADR;WORK:;;2880 Production Way;Burnaby;BC;V5A4T6;Canada LABEL;WORK;ENCODING=QUOTED-PRINTABLE:2880 Production Way=0D=0ABurnaby, BC V5A4T6=0D=0ACanada URL: URL:http://www.bmscom.com EMAIL;PREF;INTERNET:[EMAIL PROTECTED] REV:20000921T155409Z END:VCARD
