VTP, Portfast, Spanning Tree and all the other switch related stuff.
3 posts • Page 1 of 1
Hi everbody. I was doing ping with parameter -a, when i encountered something strange. here is what i did. ping help.com I got the ip address from above command as 188.8.131.52 Then i used the command :ping -a 184.108.40.206 My understanding was ping will also give me host name because we are using parameter - a, it did give me host name as: c13-ss-help-www-lb.cnet.com.I performed ip look up using http://ip-lookup.net/?220.127.116.11 I found entry as: 18.104.22.168--------- c13-ss-help-www-lb.cnet.com Here is my question, when i clicked this link i was able to get to www.help.com ,thereby proving the ip address 22.214.171.124 is indeed mapped to www help.com. But when i moved the cursor over cnet.com" right after the period between lb and cnet in the link, i was directed to www.cnet.com.They are two complete host name mapped to 126.96.36.199. How is it possible? Also when i pinged www.cnet.com i get the ip address as 188.8.131.52 . But as mentioned above www.cnet.com is mapped to 184.108.40.206 May be i am not reading the mapping " 220.127.116.11--- c13-ss-help-www-lb.cnet.com" properly thanks and have a good weekend.
Sarah These are the DNS lookups for the entries you are asking about - 18.104.22.168.in-addr.arpa. PTR 300 c13-ss-help-www-lb.cnet.com. www.help.com. CNAME 300 c13-ss-help-www-lb.cnet.com. 22.214.171.124.in-addr.arpa. PTR 300 c13-sha-stack2-netscaler2.cnet.com. Note the second entry for www.help.com is a CNAME and not a PTR like the other 2. A CNAME or Canonical Name record is simply a way to map one DNS name to another so if you enter "www.help.com" then a DNS lookup is done and the response is c13-ss-help-www-lb.cnet.com. This response will then be looked up again to get an IP address ie. the first entry above will provide this. So its simply a way of having multiple "names" mapped to a DNS names eg. www.help.com, ftp.help.com, smtp.help.com could if you wanted all be mapped to c13-ss-help-www-lb.cnet.com. And that is why you are seeing multiple names mapped to the same IP. Jon