# Unexpected DHCP Behavior During Unified ISSU

The following aspects of DHCP behavior during unified ISSU are different than the behavior during normal router operations.

## DHCP Packet Capture Halted on Line Modules

The DHCP packet capture application supports unified ISSU in that its configuration does not halt a unified in-service software upgrade. However, packet capture on line modules is halted during the upgrade phase. Packets are not captured and buffered for later forwarding to the SRP module during this phase. Capture resumes automatically during the service restoration phase.

#### Related Documentation

- Application Support for Unified ISSU