As highlighted compared to other GSM nodes, the EIR is not mandatory. Several GSM Networks were launched without an EIR.
To reduce on SCCP signalling messages (e.g. CheckIMEI()) the MSC/VLRs can be configured so that a query to the EIR will not be required for every call, i.e. the query requests can be reduced.
VBR/ Wallis Dudhnath