Hello, > while mucking around with reverse DNS for a /29 public netblock i use, i noticed > that my ISP, SBC, had only aliased 6 of the 8 IPs in the /29 block for use with > rDNS. after seeing this, i did a bit of homework and found graham toal's > explanation of the "missing" IPs ( http://www.gtoal.com/subnet.html ) which > presents this issue quite clearly. this did leave me with some additional > questions though.
it's very important to understand how ip subnetting and routing is working. Many people didn't understand (like dns). That's why even companies like microsoft have problems in there networks / dns. Read it carefully and think about. Having a deeper look into the RFCs is also a got idea. > i have been hosting websites on these reserved boundary IPs in the /29 block > with no trouble using binat. should i not be doing this since these are reserved > IPs for broadcast? i have moved one domain from the boundary already since it > needed rDNS setup. how regularly are these reserved broadcast addresses at the > beginning and end of the netblock used and for what sorts of services? These reserved ip-addresses are needed so it's very regular. Using binat is a way to avoid loosing ip-addresses but it's unusual. There is no problem in using them (like you did) but it's also normal that you cannot set rdns entries for those. Normaly you route a net and do not binat them, therefore the two reversed ip-adresses are needed. Talk to you isp and ask him if he can set your rdns entries manually. > cheers, > jake Regards Hagen Volpers
