Squid (Debian GNU/Linux 3.4.8-6+deb8u4) 経由で www.ieee.org にアクセスすると，以下のようなエラーが表示されるようになった．
Bad Request
Bad Request
An error occurred. Please contact your System Administrator.
Copyright 2017 © IEEE . All rights reserved. Use of this Web site signifies your agreement to the IEEE Terms and Conditions.A not-for-profit organization, IEEE is the world's largest professional association for the advancement of technology.squid.conf で forwarded_for off としているのだが，off だと X-Forwarded-For: unknown というヘッダ情報を送るらしい．X-Forwarded-For を付けない設定とするには delete とする必要があるらしい．以下 squid.conf より．
- on (default): X-Forwarded-For: 192.1.2.3
- off: X-Forwarded-For: unknown
- transparent: Squid will not alter the X-Forwarded-For header in any way.
- delete: Squid will delete the entire X-Forwarded-For header.
- truncate: Squid will remove all existing X-Forwarded-For entries, and place the client IP as the sole entry.