Mac Yosemite 无法 ping IPv6 地址？

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能打开网页，上网正常。
所有IPv6地址正常，Google不翻墙即可访问，YouTube可以直接https打开。
各高校的IPv6 PT站点也都正常，但就是无法ping任何一个IPv6地址。
直接ping，无法解析域名。

MBA:~ Delbert$ ping pt.zhixing.edu.cn
ping: cannot resolve pt.zhixing.edu.cn: Unknown host
MBA:~ Delbert$ ping ipv6.google.com
ping: cannot resolve ipv6.google.com: Unknown host

dig没有任何问题：

MBA:~ Delbert$ dig ipv6.google.com

; <<>> DiG 9.8.3-P1 <<>> ipv6.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49481
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;ipv6.google.com.       IN  A

;; ANSWER SECTION:
ipv6.google.com.    552142  IN  CNAME   ipv6.l.google.com.

;; AUTHORITY SECTION:
l.google.com.       60  IN  SOA ns4.google.com. dns-admin.google.com. 1578974 900 900 1800 60

;; Query time: 257 msec
;; SERVER: 2001:470:20::2#53(2001:470:20::2)
;; WHEN: Mon Jan 12 23:37:36 2015
;; MSG SIZE  rcvd: 104

MBA:~ Delbert$ dig pt.zhixing.bjtu.edu.cn

; <<>> DiG 9.8.3-P1 <<>> pt.zhixing.bjtu.edu.cn
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17663
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;pt.zhixing.bjtu.edu.cn.        IN  A

;; AUTHORITY SECTION:
zhixing.bjtu.edu.cn.    6   IN  SOA dns.zhixing.bjtu.edu.cn. zhixing.bjtu.edu.cn. 2013103001 900 900 1800 900

;; Query time: 666 msec
;; SERVER: 2001:470:20::2#53(2001:470:20::2)
;; WHEN: Mon Jan 12 23:40:07 2015
;; MSG SIZE  rcvd: 80