不是被墙，是 Amazon 的 DNS 分区解析配错导致没有 A 记录。
使用 TCP 解析或者用冷门 DNS（如
https://anonymous-proxy-servers.net/wiki/index.php/Censorship-free_DNS_servers 所列）可以得到正确的 A 记录。
$ dig '@91.239.100.100'
www.ted.com; <<>> DiG 9.9.5-W1 <<>> @
91.239.100.100
www.ted.com ; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6201
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 4, ADDITIONAL: 3
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;
www.ted.com. IN A
;; ANSWER SECTION:
www.ted.com. 76335 IN CNAME
stacked.route53.ted.com.
stacked.route53.ted.com. 30 IN A 54.217.205.210
;; AUTHORITY SECTION:
route53.ted.com. 67019 IN NS
ns-821.awsdns-38.net.
route53.ted.com. 67019 IN NS
ns-49.awsdns-06.com.
route53.ted.com. 67019 IN NS
ns-2025.awsdns-61.co.uk.
route53.ted.com. 67019 IN NS
ns-1201.awsdns-22.org.
;; ADDITIONAL SECTION:
ns-49.awsdns-06.com. 149932 IN A 205.251.192.49
ns-821.awsdns-38.net. 150195 IN A 205.251.195.53
;; Query time: 354 msec
;; SERVER: 91.239.100.100#53(91.239.100.100)
;; WHEN: Thu Mar 05 18:38:15 中国标准时间 2015
;; MSG SIZE rcvd: 254