Tra Cứu Mạng
Bản ghi DNS, cổng thông dụng, mã trạng thái HTTP và tiêu đề giao thức — bốn nội dung tra cứu trong một công cụ dạng thẻ.
Tra Cứu Bản Ghi DNS
Tương tácTham chiếu tương tác cho các loại bản ghi DNS.
- Trình tạo lệnh
Description
Syntax Format
Example
Use Cases
TTL Recommendation
Security Notes
Command Builder
DKIM/SPF/DMARC use TXT records at specific subdomains.
dig example.com Anslookup -type=A example.comRoot Zone
The DNS hierarchy starts at the root (.) — 13 logical root name servers (a.root-servers.net through m.root-servers.net) handle queries for top-level domains.
Top-Level Domains (TLDs)
Managed by registries. Examples: .com, .org, .net (generic), .uk, .de (country-code), .app, .dev (new gTLDs). TLD servers delegate to authoritative name servers for each domain.
Authoritative Name Servers
These servers hold the actual DNS records for a domain. NS records point to them. They're the final authority for queries about that domain's records.
DNS Resolution Flow
- Stub resolver checks local cache
- Query recursive resolver (ISP or public DNS like 8.8.8.8)
- Recursive resolver queries root servers
- Root refers to TLD servers
- TLD refers to authoritative name servers
- Authoritative server returns the record
- Result is cached at each level
Tra Cứu Cổng
Chính thức IANACơ sở dữ liệu cổng IANA với mức độ rủi ro bảo mật.
- Cờ bảo mật
- Chỉ phía trình duyệt
Search Ports
Quick Stats
Total Ports
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Filtered
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Results
| Port | Service | Protocol | Description | Risk |
|---|---|---|---|---|
| Start typing to search for ports... | ||||
Top 50 Most Common Ports
Port Number Ranges
| Range | Name | Description |
|---|---|---|
0-1023 | Well-Known | Reserved for system services (HTTP, SSH, etc.) |
1024-49151 | Registered | User-registered ports for applications |
49152-65535 | Dynamic/Private | Ephemeral ports for client connections |
High Risk Ports
| Port | Service | Risk |
|---|---|---|
21 | FTP | Unencrypted file transfers |
23 | Telnet | Plain text authentication |
25 | SMTP | Email spam relay risk |
53 | DNS | DDoS amplification attacks |
445 | SMB | Ransomware propagation |
3389 | RDP | Brute force attacks |
Security Best Practices
- Close unused ports: Reduce attack surface by disabling services you don't need
- Use firewalls: Implement network-level access controls
- Monitor traffic: Log connections to sensitive ports (22, 443, 3389)
- Prefer encrypted protocols: Use SSH (22) instead of Telnet (23), SFTP instead of FTP
- Change defaults: Consider non-standard ports for SSH/RDP (security through obscurity)
Tra Cứu Mã Trạng Thái HTTP
RFC 9110Tra cứu các mã trạng thái HTTP tiêu chuẩn kèm hướng dẫn sử dụng và bộ nhớ đệm.
- Có thể tìm kiếm
- Chỉ xử lý trên trình duyệt
Search HTTP statuses
Search by code, phrase, class, description, or when-to-use guidance.
Status codes
Showing all HTTP status codes.
Class meanings
| Class | Meaning | Typical use |
|---|---|---|
1xx | Informational | Interim responses while a request continues. |
2xx | Successful | The request was received, understood, and accepted. |
3xx | Redirection | The client needs another request or cached representation. |
4xx | Client Error | The request has a client-side problem or cannot be fulfilled. |
5xx | Server Error | The server failed to fulfill an apparently valid request. |
Safety, idempotency, and caching
Status codes do not make a request safe or idempotent by themselves. Safety and idempotency come from the request method and application semantics.
RFC caching rules allow some responses to be reused by default, including common statuses such as 200, 203, 204, 206, 300, 301, 308, 404, 405, 410, 414, and 501. Other statuses generally need explicit cache headers.
Tra Cứu Tiêu Đề Giao Thức
Khám phá tiêu đề giao thức HTTP/SMTP/DNS.
Field Details
Click on any field in the diagram to see details.
Ethernet II Header
14 bytesEthernet II
| Field | Size | Description |
|---|---|---|
| Destination MAC | 6 bytes | Target hardware address |
| Source MAC | 6 bytes | Sender hardware address |
| EtherType | 2 bytes | Protocol type (0x0800=IPv4, 0x86DD=IPv6) |
IPv4 Header
| Field | Size | Description |
|---|---|---|
| Version | 4 bits | IP version (4) |
| IHL | 4 bits | Header length in 32-bit words |
| TOS | 1 byte | Type of Service / DSCP |
| Total Length | 2 bytes | Total packet size |
| TTL | 1 byte | Time to Live (hop limit) |
| Protocol | 1 byte | Next protocol (6=TCP, 17=UDP) |
| Checksum | 2 bytes | Header checksum |
TCP Header
| Field | Size | Description |
|---|---|---|
| Source Port | 2 bytes | Sender port number |
| Dest Port | 2 bytes | Receiver port number |
| Seq Number | 4 bytes | Sequence number |
| Ack Number | 4 bytes | Acknowledgment number |
| Data Offset | 4 bits | Header length / 4 |
| Flags | 9 bits | NS,CWR,ECE,URG,ACK,PSH,RST,SYN,FIN |
| Window | 2 bytes | Receive window size |
Common EtherTypes
| Value | Protocol |
|---|---|
0x0800 | IPv4 |
0x0806 | ARP |
0x86DD | IPv6 |
0x8100 | VLAN (802.1Q) |