因此，我偶然 ping 了一下 abc.com，发现了以下有趣的事情：
$ ping abc.com
PING abc.com (199.181.132.250) 56(84) bytes of data.
64 bytes from m.abc.com (199.181.132.250): icmp_req=1 ttl=237 time=90.3 ms
64 bytes from tdl.disneyuniversity.com (199.181.132.250): icmp_req=2 ttl=237 time=89.8 ms
64 bytes from preschooltime.go.com (199.181.132.250): icmp_req=3 ttl=237 time=95.1 ms
64 bytes from futbolpicante.espnfc.com (199.181.132.250): icmp_req=4 ttl=237 time=98.6 ms
64 bytes from www.worldofcars.go.com (199.181.132.250): icmp_req=5 ttl=237 time=86.9 ms
64 bytes from www.verizon.bravesweepstakes.com (199.181.132.250): icmp_req=6 ttl=237 time=87.9 ms
64 bytes from www.directv.bravesweepstakes.com (199.181.132.250): icmp_req=7 ttl=237 time=87.9 ms
64 bytes from manup.abc.com (199.181.132.250): icmp_req=8 ttl=237 time=88.8 ms
64 bytes from m.onemoredisneyday.com (199.181.132.250): icmp_req=9 ttl=237 time=87.5 ms
64 bytes from finance.abc30.com (199.181.132.250): icmp_req=10 ttl=237 time=87.9 ms
64 bytes from finance.abc13.com (199.181.132.250): icmp_req=11 ttl=237 time=88.0 ms
...
在某种程度上，它似乎与正向 DNS 中使用的负载平衡类似，但我不明白它有什么用处。
出现这种情况是否有任何实际原因，或者仅仅是因为这些网站都托管在同一个 IP 地址后面？
答案1
nslookup 199.181.132.250 显示了一堆针对不同域名的非权威答案。但我的 ping 不会像您的一样动态变化。
答案2
看起来确实有人在开玩笑，或者服务器配置错误之类的。实际上有那么多反向记录。
顺便说一句。我怀疑这个 IP 可能被用来分发垃圾邮件，而这些主机名是为了混淆过滤器。（但这只是一个猜测）
看：
$ dig 250.132.181.199.in-addr.arpa -t PTR
;; Truncated, retrying in TCP mode.
; <<>> DiG 9.7.3 <<>> 250.132.181.199.in-addr.arpa -t PTR
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 33536
;; flags: qr rd ra; QUERY: 1, ANSWER: 195, AUTHORITY: 4, ADDITIONAL: 2
;; QUESTION SECTION:
;250.132.181.199.in-addr.arpa. IN PTR
;; ANSWER SECTION:
250.132.181.199.in-addr.arpa. 180 IN PTR m.nightofjoy.com.
250.132.181.199.in-addr.arpa. 180 IN PTR m.disneyworld.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR m.mustdodisney.com.
250.132.181.199.in-addr.arpa. 180 IN PTR m.disneytheforce.com.
250.132.181.199.in-addr.arpa. 180 IN PTR m.onemoredisneyday.com.
250.132.181.199.in-addr.arpa. 180 IN PTR s.espnradio.com.
250.132.181.199.in-addr.arpa. 180 IN PTR fb.steelgetsreal.com.
250.132.181.199.in-addr.arpa. 180 IN PTR my.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR qa.watchdisneyxd.com.
250.132.181.199.in-addr.arpa. 180 IN PTR qa.watchabcfamily.com.
250.132.181.199.in-addr.arpa. 180 IN PTR qa.watchdisneyjunior.com.
250.132.181.199.in-addr.arpa. 180 IN PTR qa.watchdisneychannel.com.
250.132.181.199.in-addr.arpa. 180 IN PTR uk.disneycareers.com.
250.132.181.199.in-addr.arpa. 180 IN PTR abc.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR cdn.musiclounge.abc.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR fdj.espnfc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR fdj.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR gma.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR hdf.espnfc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR hub.disneyuniversity.com.
250.132.181.199.in-addr.arpa. 180 IN PTR itm.abc.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR lnb.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR sam.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR tdl.disneyuniversity.com.
250.132.181.199.in-addr.arpa. 180 IN PTR ugc.lionking.com.
250.132.181.199.in-addr.arpa. 180 IN PTR ugc.marypoppins.com.
250.132.181.199.in-addr.arpa. 180 IN PTR ugv.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR vpd.disneycruise.com.
250.132.181.199.in-addr.arpa. 180 IN PTR w88.m.fwfest.waltdisneyworld.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.abc.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.att.bravesweepstakes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.cox.bravesweepstakes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.ttdl.disneyuniversity.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.enter.bravesweepstakes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.espnfc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.charter.bravesweepstakes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.directv.bravesweepstakes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.verizon.bravesweepstakes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.mediacom.bravesweepstakes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.adventure.bravesweepstakes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneyhome.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.worldofcars.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneycasting.net.
250.132.181.199.in-addr.arpa. 180 IN PTR www.donovandecker.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneyroommate.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneycampusrep.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneycollateral.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneyinternsinfo.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.missiontimekeeper.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneycastingscout.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneyimaginations.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneyprogramsblog.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.wdwcollegeprogramecard.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.wdwcollegeprogramecard2.com.
250.132.181.199.in-addr.arpa. 180 IN PTR www.disneyinternationalepresentation.com.
250.132.181.199.in-addr.arpa. 180 IN PTR 1ext.doit.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR 25th.disneystore.com.
250.132.181.199.in-addr.arpa. 180 IN PTR beta.xgames.com.
250.132.181.199.in-addr.arpa. 180 IN PTR blog.disneyxd.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR bmoc.abc7chicago.com.
250.132.181.199.in-addr.arpa. 180 IN PTR doit.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR live.dadt.com.
250.132.181.199.in-addr.arpa. 180 IN PTR live.espnfc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR play.toontown.com.
250.132.181.199.in-addr.arpa. 180 IN PTR prod.waltdisneystudios.com.
250.132.181.199.in-addr.arpa. 180 IN PTR ugv2.abc.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR blogs.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR cards.babyzone.com.
250.132.181.199.in-addr.arpa. 180 IN PTR email.doit.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR email.disneymovieclub.com.
250.132.181.199.in-addr.arpa. 180 IN PTR espn3.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR games.soapnet.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR manup.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR panam.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR castle.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR comedy.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR espnrf.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR hdfmas.espnfc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR health.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR mobile.abcfamily.com.
250.132.181.199.in-addr.arpa. 180 IN PTR oscars.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR photos.kaboose.com.
250.132.181.199.in-addr.arpa. 180 IN PTR photos.babyzone.com.
250.132.181.199.in-addr.arpa. 180 IN PTR search.abc.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR search.video.movies.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR temail.disneymovieclub.com.
250.132.181.199.in-addr.arpa. 180 IN PTR tienda.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR topics.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR velti2.disneylandsummer.com.
250.132.181.199.in-addr.arpa. 180 IN PTR workit.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR 999test.abcnews.com.
250.132.181.199.in-addr.arpa. 180 IN PTR account.toontown.com.
250.132.181.199.in-addr.arpa. 180 IN PTR casting.disneyparks.jobs.
250.132.181.199.in-addr.arpa. 180 IN PTR catalog.disneyuniversity.com.
250.132.181.199.in-addr.arpa. 180 IN PTR clarity.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR culture.disneyuniversity.com.
250.132.181.199.in-addr.arpa. 180 IN PTR finance.6abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR finance.abc7.com.
250.132.181.199.in-addr.arpa. 180 IN PTR finance.abc11.com.
250.132.181.199.in-addr.arpa. 180 IN PTR finance.abc13.com.
250.132.181.199.in-addr.arpa. 180 IN PTR finance.abc30.com.
250.132.181.199.in-addr.arpa. 180 IN PTR finance.7online.com.
250.132.181.199.in-addr.arpa. 180 IN PTR finance.abc7news.com.
250.132.181.199.in-addr.arpa. 180 IN PTR finance.abc7chicago.com.
250.132.181.199.in-addr.arpa. 180 IN PTR hotseat.abc.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR missing.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR playdom.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR preview.mydisneyphotopass.com.
250.132.181.199.in-addr.arpa. 180 IN PTR revenge.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR scandal.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR scrumtv.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR search2.spanish.disneylandsummer.com.
250.132.181.199.in-addr.arpa. 180 IN PTR theview.abc.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR topics2.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR uplayit.abc7chicago.com.
250.132.181.199.in-addr.arpa. 180 IN PTR developu.disneyuniversity.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneyhd.tv.
250.132.181.199.in-addr.arpa. 180 IN PTR polo2011.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR theriver.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR whereami.doit.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR abccomedy.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR helpoffer.com.
250.132.181.199.in-addr.arpa. 180 IN PTR rugby2011.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR shelterme.6abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR stagepass.abc.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR tenis2011.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR themiddle.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR trongames.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR cougartown.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR devicedata.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneytime.disneyparks.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneyvisa.com.
250.132.181.199.in-addr.arpa. 180 IN PTR experience.disneydestinations.com.
250.132.181.199.in-addr.arpa. 180 IN PTR happyrides.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR portfolios.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR storefront.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR bodyofproof.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR copavirtual.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR desafioeuro.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneyparks.jobs.
250.132.181.199.in-addr.arpa. 180 IN PTR familytools.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR glass-house.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR hipcricket2.spanish.disneylandsummer.com.
250.132.181.199.in-addr.arpa. 180 IN PTR klubpenguin.de.
250.132.181.199.in-addr.arpa. 180 IN PTR klubpinguin.de.
250.132.181.199.in-addr.arpa. 180 IN PTR musiclounge.abc.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR preolimpico.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR radiodisney.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR suburgatory.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR weatherblog.abc13.com.
250.132.181.199.in-addr.arpa. 180 IN PTR abcdotcomedy.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR euroquiniela.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR happyendings.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR modernfamily.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR sendtofriend.abcnews.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR desafiofutmex.espnfc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR dimgpressroom.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneypackage.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneystudios.com.
250.132.181.199.in-addr.arpa. 180 IN PTR futbolpicante.espnfc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR golesdeeuropa.espnfc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR onceuponatime.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR preschooltime.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR rincontecnico.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR yourcommunity.6abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR desafiopremier.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR phineasandferb.disneymags.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneyparksblog.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneyvisaperks.com.
250.132.181.199.in-addr.arpa. 180 IN PTR elmejorejemplar.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR lastmanstanding.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR monstroussummer.disneyparks.com.
250.132.181.199.in-addr.arpa. 180 IN PTR the-glass-house.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneyconnection.com.
250.132.181.199.in-addr.arpa. 180 IN PTR avalanchesoftware.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR celebritywifeswap.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneyhumanrights.org.
250.132.181.199.in-addr.arpa. 180 IN PTR disneysecondscreen.com.
250.132.181.199.in-addr.arpa. 180 IN PTR watchdisneychannel.com.
250.132.181.199.in-addr.arpa. 180 IN PTR hablemosdefutbolmas.espndeportes.com.
250.132.181.199.in-addr.arpa. 180 IN PTR mickeystrickortreat.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneylearningstudio.com.
250.132.181.199.in-addr.arpa. 180 IN PTR shanghaidisneyresort.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneystarbuckssurvey.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneyworldsvacations.com.
250.132.181.199.in-addr.arpa. 180 IN PTR wheelchairrentaldisney.com.
250.132.181.199.in-addr.arpa. 180 IN PTR hyperionbooksforchildren.com.
250.132.181.199.in-addr.arpa. 180 IN PTR disneyparksstarbuckssurvey.com.
250.132.181.199.in-addr.arpa. 180 IN PTR m.abc.com.
250.132.181.199.in-addr.arpa. 180 IN PTR m.test.doit.go.com.
250.132.181.199.in-addr.arpa. 180 IN PTR m.fwfest.waltdisneyworld.com.
250.132.181.199.in-addr.arpa. 180 IN PTR m.abcfamily.com.
250.132.181.199.in-addr.arpa. 180 IN PTR m.bostonmed.abcnews.go.com.
;; AUTHORITY SECTION:
132.181.199.in-addr.arpa. 180 IN NS sens01.dig.com.
132.181.199.in-addr.arpa. 180 IN NS orns01.dig.com.
132.181.199.in-addr.arpa. 180 IN NS sens02.dig.com.
132.181.199.in-addr.arpa. 180 IN NS orns02.dig.com.
;; ADDITIONAL SECTION:
orns01.dig.com. 257 IN A 68.71.223.14
sens02.dig.com. 242 IN A 199.181.135.199
;; Query time: 7 msec
;; SERVER: 192.168.0.1#53(192.168.0.1)
;; WHEN: Fri Apr 19 23:24:14 2013
;; MSG SIZE rcvd: 5471
答案3
这用于“正向确认的反向 DNS”。维基百科
FCrDNS 验证可以创建一种弱形式的身份验证，即域名所有者与已获得 IP 地址的网络所有者之间存在有效关系。虽然这种身份验证很弱，但它足够强大，可以用于白名单目的，因为垃圾邮件发送者和网络钓鱼者在使用僵尸计算机进行邮件欺骗时通常无法绕过此验证。也就是说，反向 DNS 可能会验证，但它通常是声明的域名以外的其他域的一部分。
但是，据我所知，没有哪个应用程序会查看超过 1 个 PTR RR。可能是迪士尼的某些服务会查看超过 1 个 PTR RR。