Help Center/ Server Migration Service/ FAQs/ Known Errors and Solutions/ SMS.0303 Unable to Access Domain Name
Updated on 2025-07-30 GMT+08:00
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SMS.0303 Unable to Access Domain Name

Symptom

When you started the migration, the error message "SMS.0303 Unable to access domain name %s" was displayed on the SMS console.

Possible Causes

For a successful migration, the source server must access all required domain names. If any domain name fails to be connected, this error message is displayed.

The possible causes are as follows:

  • The network is abnormal, for example, the connection times out or the network is disconnected or inaccessible.
  • The access is blocked by the firewall.
  • Security alarms are generated on the source server, or the source server EIP is unbound or frozen.
  • The access is blocked by the security group of the source server.

Solutions

  • Ping another domain name.
    • If the ping operation succeeds, the network is normal.
    • If the ping operation fails, the network is abnormal. Check the local network.
  • Check the firewall settings of the source server.
  • If the access is blocked, allow the access and continue the migration.
  • Check whether security alarms are generated on the source server, or the source server EIP is unbound or frozen.
    • If the EIP is unbound, you can bind it back or use a private network for migration.
    • If the EIP is frozen, contact ECS or EIP technical support.
  • Check whether the required outbound ports are allowed in the security group of the source server.
    • If there are no outbound rules for the protocols and ports shown in Figure 1, add rules for them.
    • If there are outbound rules for the ports but Action is set to Deny, change the actions to Allow.
    • If there are outbound rules for allowing the ports but the destination IP addresses are not 0.0.0.0/0, change them to 0.0.0.0/0.
    Figure 1 Outbound rules
Parent Topic: Known Errors and Solutions