Containerization-and-DevOps

Docker Networking

Theory: Docker Networking

When you run a Docker container, it runs in an isolated environment — like an apartment in a building. Each container has:

Its own IP address (like an apartment number)
Ways to communicate with other containers (hallways)
Ways to access the internet (external mail)
Ports to receive incoming traffic (doors)

Docker Networking solves four core problems:

Problem	Solution
Container ↔ Container	Shared Docker networks with DNS
Container ↔ Host Machine	Port publishing (`-p`) or host network
Container ↔ Internet	NAT via the bridge gateway
Containers on different servers	Overlay networks (multi-host)

Docker Network Drivers

Docker provides several network drivers for different use cases:

Driver	Simple Analogy	When to Use
`bridge`	Apartment building with shared hallway	Default for single host, most common
`host`	Living in same room as host	Need max performance, no isolation needed
`overlay`	Underground tunnel connecting buildings	Multiple servers need to talk
`macvlan`	Separate house with own mailbox	Need real network IP per container
`none`	Isolated room with no doors	Complete isolation needed

we use bridge (the most common type) and host.

3. Practical

List Default Networks

docker network ls

Output:

NETWORK ID     NAME      DRIVER    SCOPE
31616f46d165   bridge    bridge    local
a949c49a1f96   host      host      local
cea44970056d   none      null      local

Explanation:
When Docker is installed, it automatically creates three networks: bridge (the default), host (shares the host’s network), and none (fully isolated, no networking).

Inspect the Default Bridge Network

docker network inspect bridge

Output (key fields):

{
    "Name": "bridge",
    "Driver": "bridge",
    "IPAM": {
        "Config": [
            {
                "Subnet": "172.17.0.0/16",
                "Gateway": "172.17.0.1"
            }
        ]
    },
    "Options": {
        "com.docker.network.bridge.name": "docker0",
        "com.docker.network.bridge.enable_ip_masquerade": "true",
        "com.docker.network.driver.mtu": "1500"
    }
}

Explanation:
The default bridge network uses the 172.17.0.0/16 subnet and routes traffic through gateway 172.17.0.1. The underlying virtual interface is named docker0. The enable_ip_masquerade: true option means containers can reach the internet via NAT.

Important: The default bridge network does NOT support DNS resolution by name. Containers can only reach each other by IP, not by container name. This is why we create a custom bridge.

Create a Custom Bridge Network

docker network create my_bridge

Output:

edabda8e9816e73a6e48c82732cfb23f3bef5dfb53c25f27434121f310821baa

Explanation:
This creates a new user-defined bridge network called my_bridge. Docker returns the full network ID upon creation.

docker network inspect my_bridge

Key output:

{
    "Name": "my_bridge",
    "Driver": "bridge",
    "IPAM": {
        "Config": [
            {
                "Subnet": "172.18.0.0/16",
                "Gateway": "172.18.0.1"
            }
        ]
    }
}

Explanation:
Docker automatically assigned my_bridge the next available subnet — 172.18.0.0/16 (since 172.17.0.0/16 was taken by the default bridge). The key advantage of a custom bridge is automatic DNS — containers can find each other by name, not just IP.

Run Containers on the Custom Network

Run container1 (nginx web server):

docker run -dit --name container1 --network my_bridge nginx

Output:

33073f88712c85a53336a0f61d3d4de085d7ea76445654e6081535fd51d4db64

Run container2 (busybox utility):

docker run -dit --name container2 --network my_bridge busybox

Output (first-time image pull):

Unable to find image 'busybox:latest' locally
latest: Pulling from library/busybox
61dfb50712f5: Pull complete
Digest: sha256:b3255e7dfbcd10cb367af0d409747d511aeb66dfac98cf30e97e87e4207dd76f
Status: Downloaded newer image for busybox:latest
d525cc4a02bbee90c344acd1992c5ef81d6f005ff4c82d76600659792b486862

Explanation of flags:

Flag	Meaning
`-d`	Detached mode — run container in background
`-i`	Interactive — keep STDIN open
`-t`	Allocate a pseudo-TTY (terminal)
`--name`	Assign a human-readable name to the container
`--network`	Connect the container to the specified network

Note: The first time an image is used, Docker pulls it from Docker Hub. Subsequent runs use the local cached image.

Test Container-to-Container Communication (by Name)

docker exec -it container2 ping container1

Output:

PING container1 (172.18.0.2): 56 data bytes
64 bytes from 172.18.0.2: seq=0 ttl=64 time=0.397 ms
64 bytes from 172.18.0.2: seq=1 ttl=64 time=0.145 ms
64 bytes from 172.18.0.2: seq=2 ttl=64 time=0.098 ms
...
44 packets transmitted, 44 packets received, 0% packet loss
round-trip min/avg/max = 0.070/0.112/0.397 ms

Explanation:
docker exec -it container2 ping container1 runs the ping command inside container2, targeting container1 by name. Docker’s embedded DNS server (running at 127.0.0.11 inside each container) resolved container1 → 172.18.0.2 automatically.

0% packet loss confirms the two containers are communicating successfully on the same custom bridge network.
Round-trip time ~0.112ms — very low latency since both containers are on the same host.

Magic moment: This only works because both containers are on the same user-defined bridge. The default bridge network does NOT support this name-based DNS.

Inspect container1 for Network Details

docker inspect container1

Key sections from the output:

State:

"State": {
    "Status": "running",
    "Running": true,
    "Pid": 11359
}

Network Settings:

"NetworkSettings": {
    "Networks": {
        "my_bridge": {
            "Gateway": "172.18.0.1",
            "IPAddress": "172.18.0.2",
            "MacAddress": "de:12:4c:c1:8f:3c",
            "DNSNames": ["container1", "33073f88712c"]
        }
    }
}

Explanation:
docker inspect returns full JSON metadata about the container. Important fields:

Field	Value	Meaning
`Status`	`running`	Container is actively running
`Pid`	`11359`	Host process ID of the container’s main process
`IPAddress`	`172.18.0.2`	Container’s IP on `my_bridge`
`MacAddress`	`de:12:4c:c1:8f:3c`	Virtual MAC address assigned by Docker
`Gateway`	`172.18.0.1`	Traffic to outside the network routes through this
`DNSNames`	`container1`, `33073f88712c`	Names usable for DNS resolution

Extract IP Address

docker inspect container1 | grep IP

Output:

"IPAMConfig": null,
"IPAddress": "172.18.0.2",
"IPPrefixLen": 16,
"IPv6Gateway": "",
"GlobalIPv6Address": "",
"GlobalIPv6PrefixLen": 0,

Explanation:
This is a quick way to grep just the IP-related fields without reading the full JSON. container1 has been assigned 172.18.0.2 on the my_bridge network with a /16 prefix (subnet mask 255.255.0.0).

Better alternative (from theory):
docker inspect -f '' container1
This returns just the IP address cleanly.

Test Cross-Network Isolation

docker exec -it container2 ping 172.17.0.2

Output:

PING 172.17.0.2 (172.17.0.2): 56 data bytes
--- 172.17.0.2 ping statistics ---
13 packets transmitted, 0 packets received, 100% packet loss

Explanation:
172.17.0.2 is an IP in the default bridge network (172.17.0.0/16). container2 lives in my_bridge (172.18.0.0/16). Since these are two separate networks, Docker’s isolation rules prevent communication — 100% packet loss is the expected, correct result.

This proves network isolation works: Containers on different Docker networks cannot talk to each other unless explicitly connected.

Host Network Mode

docker run -d --network host nginx

Output:

2a2b1405645cab1c4085613d4863b7826526058f45b7212ee0272201f3104b83

Verify nginx is listening on the host:

ss -tulnp | grep 80

Output:

tcp   LISTEN 0   100       0.0.0.0:6080     0.0.0.0:*    users:(("nova-novncproxy",...))
tcp   LISTEN 0   511             *:80             *:*
tcp   LISTEN 0   4096            *:2380           *:*

Explanation:
--network host removes all network isolation between the container and the host. Nginx inside the container now binds directly to port 80 on the host machine — no -p port mapping needed.

The ss -tulnp command lists all listening TCP/UDP sockets:

Column	Meaning
`tcp LISTEN`	A listening TCP socket
`*:80`	Listening on all interfaces on port 80
`0.0.0.0:6080`	Another process on port 6080

When NOT to use host network:

When you need isolation (containers may conflict with host services)
On Docker Desktop for Mac/Windows (limited support)
When running multiple containers needing the same ports

Key Observations

Observation	What It Proves
`container2` pings `container1` by name successfully	Custom bridge networks have built-in DNS
`172.17.0.0/16` for default bridge, `172.18.0.0/16` for `my_bridge`	Docker auto-assigns non-overlapping subnets
100% packet loss when pinging across networks	Network isolation works correctly
`*:80` appears in `ss` output after `--network host`	Host network shares the host’s port space directly
busybox image pulled automatically	Docker Hub is the default image registry

MACVLAN VS IPVLAN

Quick Reference Cheatsheet

Network Management

Command	Description
`docker network ls`	List all networks
`docker network create mynet`	Create a new bridge network
`docker network inspect mynet`	Show detailed network info
`docker network rm mynet`	Delete a network
`docker network prune`	Remove all unused networks
`docker network connect mynet container`	Add a running container to a network
`docker network disconnect mynet container`	Remove container from network

Running Containers with Networks

Command	Description
`docker run --network mynet ...`	Start container in specific network
`docker run -p 8080:80 ...`	Map host port 8080 to container port 80
`docker run -p 127.0.0.1:8080:80 ...`	Bind only to localhost
`docker run -P ...`	Auto-assign random host ports
`docker run --network host ...`	Use host’s network directly

WSL Command

aniket@Aniket:~$ docker network ls
NETWORK ID     NAME      DRIVER    SCOPE
31616f46d165   bridge    bridge    local
a949c49a1f96   host      host      local
cea44970056d   none      null      local
aniket@Aniket:~$ docker network inspect bridge
[
    {
        "Name": "bridge",
        "Id": "31616f46d165049ee9c62fd82cea0536491313c7a4bd9b63858b1849a333b663",
        "Created": "2026-02-18T14:38:09.64660814+05:30",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv4": true,
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "172.17.0.0/16",
                    "IPRange": "",
                    "Gateway": "172.17.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Options": {
            "com.docker.network.bridge.default_bridge": "true",
            "com.docker.network.bridge.enable_icc": "true",
            "com.docker.network.bridge.enable_ip_masquerade": "true",
            "com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
            "com.docker.network.bridge.name": "docker0",
            "com.docker.network.driver.mtu": "1500"
        },
        "Labels": {},
        "Containers": {},
        "Status": {
            "IPAM": {
                "Subnets": {
                    "172.17.0.0/16": {
                        "IPsInUse": 3,
                        "DynamicIPsAvailable": 65533
                    }
                }
            }
        }
    }
]
aniket@Aniket:~$ docker network create my_bridge
edabda8e9816e73a6e48c82732cfb23f3bef5dfb53c25f27434121f310821baa
aniket@Aniket:~$ docker network inspect my_bridge
[
    {
        "Name": "my_bridge",
        "Id": "edabda8e9816e73a6e48c82732cfb23f3bef5dfb53c25f27434121f310821baa",
        "Created": "2026-02-18T14:42:19.71029279+05:30",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv4": true,
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "172.18.0.0/16",
                    "IPRange": "",
                    "Gateway": "172.18.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Options": {},
        "Labels": {},
        "Containers": {},
        "Status": {
            "IPAM": {
                "Subnets": {
                    "172.18.0.0/16": {
                        "IPsInUse": 3,
                        "DynamicIPsAvailable": 65533
                    }
                }
            }
        }
    }
]
aniket@Aniket:~$ docker run -dit --name container1 --network my_bridge nginx
33073f88712c85a53336a0f61d3d4de085d7ea76445654e6081535fd51d4db64
aniket@Aniket:~$ docker run -dit --name container2 --network my_bridge busybox
Unable to find image 'busybox:latest' locally
latest: Pulling from library/busybox
61dfb50712f5: Pull complete
96cfb76e59bd: Download complete
Digest: sha256:b3255e7dfbcd10cb367af0d409747d511aeb66dfac98cf30e97e87e4207dd76f
Status: Downloaded newer image for busybox:latest
d525cc4a02bbee90c344acd1992c5ef81d6f005ff4c82d76600659792b486862
aniket@Aniket:~$ docker exec -it container2 ping container1
PING container1 (172.18.0.2): 56 data bytes
64 bytes from 172.18.0.2: seq=0 ttl=64 time=0.397 ms
64 bytes from 172.18.0.2: seq=1 ttl=64 time=0.145 ms
64 bytes from 172.18.0.2: seq=2 ttl=64 time=0.098 ms
64 bytes from 172.18.0.2: seq=3 ttl=64 time=0.105 ms
64 bytes from 172.18.0.2: seq=4 ttl=64 time=0.103 ms
64 bytes from 172.18.0.2: seq=5 ttl=64 time=0.117 ms
64 bytes from 172.18.0.2: seq=6 ttl=64 time=0.101 ms
64 bytes from 172.18.0.2: seq=7 ttl=64 time=0.087 ms
64 bytes from 172.18.0.2: seq=8 ttl=64 time=0.116 ms
64 bytes from 172.18.0.2: seq=9 ttl=64 time=0.096 ms
64 bytes from 172.18.0.2: seq=10 ttl=64 time=0.075 ms
64 bytes from 172.18.0.2: seq=11 ttl=64 time=0.096 ms
64 bytes from 172.18.0.2: seq=12 ttl=64 time=0.129 ms
64 bytes from 172.18.0.2: seq=13 ttl=64 time=0.120 ms
64 bytes from 172.18.0.2: seq=14 ttl=64 time=0.089 ms
64 bytes from 172.18.0.2: seq=15 ttl=64 time=0.100 ms
64 bytes from 172.18.0.2: seq=16 ttl=64 time=0.107 ms
64 bytes from 172.18.0.2: seq=17 ttl=64 time=0.126 ms
64 bytes from 172.18.0.2: seq=18 ttl=64 time=0.075 ms
64 bytes from 172.18.0.2: seq=19 ttl=64 time=0.095 ms
64 bytes from 172.18.0.2: seq=20 ttl=64 time=0.076 ms
64 bytes from 172.18.0.2: seq=21 ttl=64 time=0.116 ms
64 bytes from 172.18.0.2: seq=22 ttl=64 time=0.090 ms
64 bytes from 172.18.0.2: seq=23 ttl=64 time=0.096 ms
64 bytes from 172.18.0.2: seq=24 ttl=64 time=0.142 ms
64 bytes from 172.18.0.2: seq=25 ttl=64 time=0.116 ms
64 bytes from 172.18.0.2: seq=26 ttl=64 time=0.081 ms
64 bytes from 172.18.0.2: seq=27 ttl=64 time=0.078 ms
64 bytes from 172.18.0.2: seq=28 ttl=64 time=0.075 ms
64 bytes from 172.18.0.2: seq=29 ttl=64 time=0.079 ms
64 bytes from 172.18.0.2: seq=30 ttl=64 time=0.082 ms
^C
--- container1 ping statistics ---
44 packets transmitted, 44 packets received, 0% packet loss
round-trip min/avg/max = 0.070/0.112/0.397 ms
aniket@Aniket:~$ docker inspect container1
[
    {
        "Id": "33073f88712c85a53336a0f61d3d4de085d7ea76445654e6081535fd51d4db64",
        "Created": "2026-02-18T09:14:28.505803359Z",
        "Path": "/docker-entrypoint.sh",
        "Args": [
            "nginx",
            "-g",
            "daemon off;"
        ],
        "State": {
            "Status": "running",
            "Running": true,
            "Paused": false,
            "Restarting": false,
            "OOMKilled": false,
            "Dead": false,
            "Pid": 11359,
            "ExitCode": 0,
            "Error": "",
            "StartedAt": "2026-02-18T09:14:28.758838469Z",
            "FinishedAt": "0001-01-01T00:00:00Z"
        },
        "Image": "sha256:9dd288848f4495869f76676e419ae2d767ca99fece2ec37ec0261f9fdaab5204",
        "ResolvConfPath": "/var/lib/docker/containers/33073f88712c85a53336a0f61d3d4de085d7ea76445654e6081535fd51d4db64/resolv.conf",
        "HostnamePath": "/var/lib/docker/containers/33073f88712c85a53336a0f61d3d4de085d7ea76445654e6081535fd51d4db64/hostname",
        "HostsPath": "/var/lib/docker/containers/33073f88712c85a53336a0f61d3d4de085d7ea76445654e6081535fd51d4db64/hosts",
        "LogPath": "/var/lib/docker/containers/33073f88712c85a53336a0f61d3d4de085d7ea76445654e6081535fd51d4db64/33073f88712c85a53336a0f61d3d4de085d7ea76445654e6081535fd51d4db64-json.log",
        "Name": "/container1",
        "RestartCount": 0,
        "Driver": "overlayfs",
        "Platform": "linux",
        "MountLabel": "",
        "ProcessLabel": "",
        "AppArmorProfile": "",
        "ExecIDs": null,
        "HostConfig": {
            "Binds": null,
            "ContainerIDFile": "",
            "LogConfig": {
                "Type": "json-file",
                "Config": {}
            },
            "NetworkMode": "my_bridge",
            "PortBindings": {},
            "RestartPolicy": {
                "Name": "no",
                "MaximumRetryCount": 0
            },
            "AutoRemove": false,
            "VolumeDriver": "",
            "VolumesFrom": null,
            "ConsoleSize": [
                43,
                76
            ],
            "CapAdd": null,
            "CapDrop": null,
            "CgroupnsMode": "private",
            "Dns": null,
            "DnsOptions": [],
            "DnsSearch": [],
            "ExtraHosts": null,
            "GroupAdd": null,
            "IpcMode": "private",
            "Cgroup": "",
            "Links": null,
            "OomScoreAdj": 0,
            "PidMode": "",
            "Privileged": false,
            "PublishAllPorts": false,
            "ReadonlyRootfs": false,
            "SecurityOpt": null,
            "UTSMode": "",
            "UsernsMode": "",
            "ShmSize": 67108864,
            "Runtime": "runc",
            "Isolation": "",
            "CpuShares": 0,
            "Memory": 0,
            "NanoCpus": 0,
            "CgroupParent": "",
            "BlkioWeight": 0,
            "BlkioWeightDevice": [],
            "BlkioDeviceReadBps": [],
            "BlkioDeviceWriteBps": [],
            "BlkioDeviceReadIOps": [],
            "BlkioDeviceWriteIOps": [],
            "CpuPeriod": 0,
            "CpuQuota": 0,
            "CpuRealtimePeriod": 0,
            "CpuRealtimeRuntime": 0,
            "CpusetCpus": "",
            "CpusetMems": "",
            "Devices": [],
            "DeviceCgroupRules": null,
            "DeviceRequests": null,
            "MemoryReservation": 0,
            "MemorySwap": 0,
            "MemorySwappiness": null,
            "OomKillDisable": null,
            "PidsLimit": null,
            "Ulimits": [],
            "CpuCount": 0,
            "CpuPercent": 0,
            "IOMaximumIOps": 0,
            "IOMaximumBandwidth": 0,
            "MaskedPaths": [
                "/proc/acpi",
                "/proc/asound",
                "/proc/interrupts",
                "/proc/kcore",
                "/proc/keys",
                "/proc/latency_stats",
                "/proc/sched_debug",
                "/proc/scsi",
                "/proc/timer_list",
                "/proc/timer_stats",
                "/sys/devices/virtual/powercap",
                "/sys/firmware"
            ],
            "ReadonlyPaths": [
                "/proc/bus",
                "/proc/fs",
                "/proc/irq",
                "/proc/sys",
                "/proc/sysrq-trigger"
            ]
        },
        "Storage": {
            "RootFS": {
                "Snapshot": {
                    "Name": "overlayfs"
                }
            }
        },
        "Mounts": [],
        "Config": {
            "Hostname": "33073f88712c",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "ExposedPorts": {
                "80/tcp": {}
            },
            "Tty": true,
            "OpenStdin": true,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "NGINX_VERSION=1.29.4",
                "NJS_VERSION=0.9.4",
                "NJS_RELEASE=1~trixie",
                "ACME_VERSION=0.3.1",
                "PKG_RELEASE=1~trixie",
                "DYNPKG_RELEASE=1~trixie"
            ],
            "Cmd": [
                "nginx",
                "-g",
                "daemon off;"
            ],
            "Image": "nginx",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": [
                "/docker-entrypoint.sh"
            ],
            "Labels": {
                "maintainer": "NGINX Docker Maintainers <docker-maint@nginx.com>"
            },
            "StopSignal": "SIGQUIT"
        },
        "NetworkSettings": {
            "SandboxID": "50bacfd41a1239c6e9a8900b7dcdee43db55c1388b522a31f4e11b4f2542c019",
            "SandboxKey": "/var/run/docker/netns/50bacfd41a12",
            "Ports": {
                "80/tcp": null
            },
            "Networks": {
                "my_bridge": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": null,
                    "DriverOpts": null,
                    "GwPriority": 0,
                    "NetworkID": "edabda8e9816e73a6e48c82732cfb23f3bef5dfb53c25f27434121f310821baa",
                    "EndpointID": "0921c48710f5080e4f112533ea5bbea2f2b639c1beb0848c8f5cd50b64a08d0e",
                    "Gateway": "172.18.0.1",
                    "IPAddress": "172.18.0.2",
                    "MacAddress": "de:12:4c:c1:8f:3c",
                    "IPPrefixLen": 16,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "DNSNames": [
                        "container1",
                        "33073f88712c"
                    ]
                }
            }
        },
        "ImageManifestDescriptor": {
            "mediaType": "application/vnd.oci.image.manifest.v1+json",
            "digest": "sha256:7561cad9fdf9dd48792ffb11c91196b273dcac65938b43fe4d1659179f5d289d",
            "size": 2290,
            "annotations": {
                "com.docker.official-images.bashbrew.arch": "amd64",
                "org.opencontainers.image.base.digest": "sha256:346fa035ca82052ce8ec3ddb9df460b255507acdeb1dc880a8b6930e778a553c",
                "org.opencontainers.image.base.name": "debian:trixie-slim",
                "org.opencontainers.image.created": "2026-02-03T02:22:34Z",
                "org.opencontainers.image.revision": "a306285ea2e4267c63ca539c66e8bc242bdce917",
                "org.opencontainers.image.source": "https://github.com/nginx/docker-nginx.git#a306285ea2e4267c63ca539c66e8bc242bdce917:mainline/debian",
                "org.opencontainers.image.url": "https://hub.docker.com/_/nginx",
                "org.opencontainers.image.version": "1.29.4"
            },
            "platform": {
                "architecture": "amd64",
                "os": "linux"
            }
        }
    }
]
aniket@Aniket:~$ docker inspect container1 | grep IP
                    "IPAMConfig": null,
                    "IPAddress": "172.18.0.2",
                    "IPPrefixLen": 16,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
aniket@Aniket:~$ docker exec -it container2 ping 172.17.0.2
PING 172.17.0.2 (172.17.0.2): 56 data bytes
^C
--- 172.17.0.2 ping statistics ---
13 packets transmitted, 0 packets received, 100% packet loss
aniket@Aniket:~$ docker run -d --network host nginx
2a2b1405645cab1c4085613d4863b7826526058f45b7212ee0272201f3104b83
aniket@Aniket:~$ ss -tulnp | grep 80
tcp   LISTEN 0      100           0.0.0.0:6080       0.0.0.0:*    users:(("nova-novncproxy",pid=357,fd=6))
tcp   LISTEN 0      511                 *:80               *:*
tcp   LISTEN 0      4096                *:2380             *:*
aniket@Aniket:~$