ltm rule command NAME lookup
iRule(1) BIG-IP TMSH Manual iRule(1)
NAME::lookup
Performs DNS query for A or PTR record corresponding to a hostname or
IP address.
SYNOPSIS
NAME::lookup (((AT_SERVER)?
('inet' | 'inet6')
('-a' | '-aaaa' | '-txt' | '-mx' | '-srv' |
'-naptr' | '-ptr')
)#)? HOST_NAME
DESCRIPTION
Performs a DNS query, typically returning the A record for the
indicated hostname, or the PTR record for the indicated IP address.
Starting in v10.1, the RESOLV::lookup command has been introduced,
which is the inline version of this command. With RESOLV::lookup, the
iRule execution will suspend and the result will be simply returned,
whereas NAME::lookup continues and eventually causes NAME_RESOLVED to
fire, where the NAME::response command can be used to retrieve the
lookup result.
NAME::lookup Performs DNS query, returning the PTR record
(hostname) for the indicated IP address. Only a single address should
be returned.
NAME::lookup Performs DNS query, returning the A record
(address) for the indicated hostname. If no record is found, a blank
string is returned. Multiple addresses may be returned in a tcl list
format.
If you do not include the @{IP/Virtual Name} argument, local bind will
be the target of the query. If your local bind is not set up to query
recursively, and is not authoritative for the domain in question, you
will receive no response.
RETURN VALUE
Typically returning the A record for the indicated hostname, or the PTR
record for the indicated IP address.
VALID DURING
ANY_EVENT
EXAMPLES
# Reverse resolution - get PTR (hostname) for an IP address (Note: Not all names have corresponding PTR records. Reverse resolutions are easily spoofed not guaranteed to be correct) Logs a line reading "client name = >10.10.10.1<" if resolved or "client name = ><" if not:
when HTTP_REQUEST {
# Hold HTTP data until hostname is resolved
HTTP::collect
# Start a name resolution on the hostname
NAME::lookup [IP::client_addr]
}
when NAME_RESOLVED {
log local0. "client name = >[NAME::response]<"
# Release HTTP data once hostname is resolved
HTTP::release
}
# Forward resolution - get IP address for hostname. Logs the following for resolution returning 3 addresses: "IP address list for remotehost.domain.com = >{10.10.10.1 10.10.10.2 10.10.10.3}<" "First listed address is >10.10.10.1<" "Second listed address is >10.10.10.2<"
when HTTP_RESPONSE {
# Hold HTTP data until IP address is resolved
HTTP::collect
# Start a name resolution on the hostname
NAME::lookup remotehost.domain.com
}
when NAME_RESOLVED {
log local0. "IP address list for remotehost.domain.com = >[NAME::response]<"
log local0. "First listed address is >[lindex [NAME::response] 0]<"
log local0. "Second listed address is >[lindex [NAME::response] 1]<"
# Release HTTP data once hostname is resolved
HTTP::release
}
HINTS
SEE ALSO
- Performs a reverse DNS lookup
to validate client IP - This iRule selects
a snatpool based on which virtual called the iRule. and will select the
member servers to use based on DNS resolution.
CHANGE LOG
@BIGIP-9.0.0 --First introduced the command. @BIGIP-10.1.0 --Introduce
AT_SERVER, inet, inet6 and -a/-aaaa/-txt/-mx/-ptr options.
BIG-IP 2017-01-31 iRule(1)