Troubleshooting Container Network Impacting Host Network Access

Problem Description

Services in the 172.27.0.0/16 and 172.26.0.0/16 subnets are unable to access the host’s services.

Problem Troubleshooting

Network Configuration

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docker network ls
NETWORK ID     NAME                      DRIVER    SCOPE
8eacdcbf22d7   7b-full_default           bridge    local
f22af6f77037   bridge                    bridge    local
4a56201be716   host                      host      local
6e36d25cdbb0   llama2-13b-lora_default   bridge    local
fb2839792d18   llama3-8b_lora_default    bridge    local
d1f916892b02   none                      null      local
2c9c2578ecce   tgi_default               bridge    local
446845acbad5   v2-9b_default             bridge    local
d1301d605f3c   v2-27b-it_default         bridge    local
c3d523d51ee4   v3-8b_default             bridge    local
1d3cf7bd9665   v4-9b_default             bridge    local
59aecf59ca81   v31-8b_default            bridge    local
42cca879c18f   webui-docker_default      bridge    local

It is found that the network IDs 1d3cf7bd9665 and 1d3cf7bd9665 are using the 172.27.0.0/16 and 172.26.0.0/16 subnets, causing routing conflicts. The Linux kernel’s routing mechanism prioritizes the most matching route, which can override the default route, causing traffic to be incorrectly directed to Docker.

Solution

Modify Docker Configuration to Avoid Conflict Subnets

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{
  "bip": "192.168.100.1/24",
  "default-address-pools": [
    {
      "base": "192.168.200.0/20",
      "size": 24
    }
  ]
}

Create Containers Using Specific Networks

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docker network create --subnet=xx.xx.xx.xx/24 my_custom_network

If It Is Necessary to Keep the Conflict Subnets, Modify Host Routing to Prioritize External Networks

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ip route del 172.27.0.0/16
ip route add 172.27.0.0/16 via <external_gateway> metric 100