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client.as.number

INTEGER, read-only.

Available inall subroutines.

Autonomous system (AS) number.

The INTEGER type in VCL is wide enough to support the full range of 32-bit AS numbers.

Converting to asdot+ format

Formatting these numbers to base 10 (e.g., by implicit conversion to a STRING type) will give an asplain representation of the number, which is just its base 10 representation.

RFC 5396 introduces the asdot+ format, which represents a 32-bit AS number as two 16-bit parts. The following VCL illustrates constructing an asdot+ formatted number:

sub client_asn_dotplus STRING {
  declare local var.hi INTEGER;
  declare local var.lo INTEGER;
  declare local var.s STRING;


  set var.hi = client.as.number;
  set var.hi >>= 16;
  set var.lo = client.as.number;
  set var.lo &= 0xFFFF;


  set var.s = client.as.number ": " var.hi "." var.lo;


  return var.s;
}

Examples

The 32-bit AS number 65550 (reserved by RFC 5398 for documentation use) is rendered as 1.14.

Several ranges of AS numbers are reserved for various purposes. The following VCL fragment illustrates categorizing AS numbers into these ranges:

sub client_asn_category STRING {
  declare local var.asn_category STRING;


  if (client.as.number < 0 || client.as.number > 0xFFFFFFFF) {
    set var.asn_category = "invalid";
  } else if (client.as.number == 0) {
    set var.asn_category = "reserved"; # RFC 1930
  } else if (client.as.number <= 23455) {
    set var.asn_category = "public";
  } else if (client.as.number == 23456) {
    set var.asn_category = "transition"; # RFC 6793
  } else if (client.as.number <= 64534) {
    set var.asn_category = "public";
  } else if (client.as.number <= 64495) {
    set var.asn_category = "reserved";
  } else if (client.as.number <= 64511) {
    set var.asn_category = "documentation"; # RFC 5398
  } else if (client.as.number <= 65534) {
    set var.asn_category = "private";
  } else if (client.as.number == 65535) {
    set var.asn_category = "reserved";
  } else if (client.as.number <= 65551) {
    set var.asn_category = "documentation"; # RFC 4893, RFC 5398
  } else if (client.as.number <= 131071) {
    set var.asn_category = "reserved";
  } else if (client.as.number <= 4199999999) {
    set var.asn_category = "public";
  } else if (client.as.number <= 4294967294) {
    set var.asn_category = "private"; # RFC 6996
  } else if (client.as.number == 4294967295) {
    set var.asn_category = "reserved";
  } else {
    set var.asn_category = "unknown";
  }


  return var.asn_category;
}

Try it out

client.as.number is used in the following code examples. Examples apply VCL to real-world use cases and can be deployed as they are, or adapted for your own service. See the full list of code examples for more inspiration.

Click RUN on a sample below to provision a Fastly service, execute the code on Fastly, and see how the function behaves.

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