{"action":"closed","issue":{"url":"https://api.github.com/repos/docker/for-mac/issues/2345","repository_url":"https://api.github.com/repos/docker/for-mac","labels_url":"https://api.github.com/repos/docker/for-mac/issues/2345/labels{/name}","comments_url":"https://api.github.com/repos/docker/for-mac/issues/2345/comments","events_url":"https://api.github.com/repos/docker/for-mac/issues/2345/events","html_url":"https://github.com/docker/for-mac/issues/2345","id":283832684,"node_id":"MDU6SXNzdWUyODM4MzI2ODQ=","number":2345,"title":"Can't ping specific subnet from within a Docker container On macOS","user":{"login":"MatanRubin","id":4488227,"node_id":"MDQ6VXNlcjQ0ODgyMjc=","avatar_url":"https://avatars0.githubusercontent.com/u/4488227?v=4","gravatar_id":"","url":"https://api.github.com/users/MatanRubin","html_url":"https://github.com/MatanRubin","followers_url":"https://api.github.com/users/MatanRubin/followers","following_url":"https://api.github.com/users/MatanRubin/following{/other_user}","gists_url":"https://api.github.com/users/MatanRubin/gists{/gist_id}","starred_url":"https://api.github.com/users/MatanRubin/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/MatanRubin/subscriptions","organizations_url":"https://api.github.com/users/MatanRubin/orgs","repos_url":"https://api.github.com/users/MatanRubin/repos","events_url":"https://api.github.com/users/MatanRubin/events{/privacy}","received_events_url":"https://api.github.com/users/MatanRubin/received_events","type":"User","site_admin":false},"labels":[{"id":868280521,"node_id":"MDU6TGFiZWw4NjgyODA1MjE=","url":"https://api.github.com/repos/docker/for-mac/labels/lifecycle/stale","name":"lifecycle/stale","color":"8B4513","default":false},{"id":438330583,"node_id":"MDU6TGFiZWw0MzgzMzA1ODM=","url":"https://api.github.com/repos/docker/for-mac/labels/status/0-triage","name":"status/0-triage","color":"bfd4f2","default":false}],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":7,"created_at":"2017-12-21T10:10:23Z","updated_at":"2018-09-18T09:45:32Z","closed_at":"2018-09-18T09:45:32Z","author_association":"NONE","body":"### Expected behavior\r\nI should be able to ping from within a container whatever server the host can ping.\r\n\r\n### Actual behavior\r\nAlmost all servers I tried to ping work as expected, but servers starting with 172.20.\\*.\\* are unreachable (while the host can reach them without an issue).\r\n\r\n### Information\r\n\r\nDiagnostic ID: 72CEAFC7-61B3-4FE5-9E92-D3568802EDFF\r\nAfter creating a container (doesn't really matter which one) I enter the container using:\r\n\r\n`docker exec -it <container_name> /bin/bash`\r\n\r\nFrom with the container I can ping google.com, as well as almost every server on my workplace network. However, for some reason I cannot ping servers with IP starting with 172.20.\\*.\\*.\r\n\r\nFor example, I tried multiple servers with IPs such as 10.0.\\*.\\*, 10.50.\\*.\\* and everything worked fine. Servers starting with 172.20 are unreachable. From the Mac host I can ping all these servers without an issue. I tried the same thing on a Linux machine and a Windows machine and could not reproduce the issue.\r\n\r\nI'm assuming it's something to do with the way Docker routes the connection through the host. It might have something to do with the fact that the docker network is usually on 172.18.\\*.\\*. However, I could not figure it out.\r\n\r\nHere's the routing table from within the container:\r\n\r\n```\r\n$ route\r\nKernel IP routing table\r\nDestination     Gateway         Genmask         Flags Metric Ref    Use Iface\r\ndefault         172.18.0.1      0.0.0.0         UG    0      0        0 eth0\r\n172.18.0.0      *               255.255.0.0     U     0      0        0 eth0\r\n```\r\n\r\nRunning macOS High Sierra with Docker CE 17.09.1-ce-mac42 (21090).\r\n\r\nAny idea what's going on?"}}
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