The employee who returned from the business trip resumed work, and then the network stopped suddenly
"Don't do it" introduced this time is an example of taking a laptop computer used outside the company in a suspended state and connected to the network.This act makes many PCs accessible to the Internet.Why did that happen?
FW経由でインターネットに接続
Companies with multiple bases have accessed the Internet via the headquarters firewall (FW).Each base and headquarters were connected using the VPN service, and the headquarters was operating a shared server.
One day, the employee of the headquarters contacted the system administrator, "I can't connect to the Internet."It is accessible to the in -house shared server, but cannot access the Internet.As a way, when I asked an employee working at a base other than the headquarters, I was able to confirm the same symptoms.
インターネットに接続できないトラブルが発生インターネットに接続できないパソコンが本社内で複数台見つかった。続いてVPN接続した拠点からもインターネットに接続できなくなった。[画像のクリックで拡大表示]The administrator thought that there was a cause on the Internet, L2 switches, and routers.First, I checked the FW log.The log recorded an error in which the FW and the IP address of another device competed.
ファイアウオールのIPアドレスと重複していたファイアウオールのログを調べたところ、ファイアウオールとIPアドレスが重複している機器があることが分かった。認証ログのMACアドレスからユーザー名を特定。該当する従業員はノートパソコンを出張先のホテルで使用し、サスペンド状態で持って帰っていた。[画像のクリックで拡大表示]From the FW log, we were able to confirm the MAC address of competing devices.In this company, the devices connected by wireless LAN are authenticated at access points, and the authentication log has a MAC address and user name.So, I checked the authentication log of access points.Then the corresponding MAC address was found from the authentication log.I checked the username and found that it was an employee at the head office.
Examining the laptops used by the employee revealed that the FW IP address was set.When the administrator restarted the computer, the trouble was resolved.
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