IPPool shouldn' t send GARPs. But VIP may so if configured.
# conf fire vip
# edit <yourvip>
get
name : <yourvip>
id : 0
comment : (null)
type : static-nat
extip : 0.0.0.0
extintf : wan1
arp-reply : enable
nat-source-vip : disable
portforward : enable
gratuitous-arp-interval: 0 <<<----------------------------
mappedip : 11.22.33.44
protocol : tcp
extport : 8080
mappedport : 80
gratuitous-arp-interval interval between sending gratuitous arps (seconds)(0 to disable)
tree firewall vip
-- [vip] --*name (64)
|- id (0,65535)
|- comment (64 xss)
|- type
|- ldb-method
|- extip
|- mappedip
|- extintf (36)
|- arp-reply
|- server-type
|- persistence
|- nat-source-vip
|- portforward
|- protocol
|- extport (1,65535)
|- mappedport
|- gratuitous-arp-interval (0,0)
|- [realservers] -- ip
|- port (1,65535)
|- status
|- weight (1,255)
|- holddown-interval (0,0)
|- healthcheck
|- max-connections (0,2147483647)
|- monitor (64)
+- client-ip
|- http-cookie-domain (36)
|- http-cookie-path (36)
|- http-cookie-generation (0,0)
|- http-cookie-age (0,525600)
|- http-cookie-share
|- http-multiplex
|- http-ip-header
|- outlook-web-access
|- monitor (64)
+- max-embryonic-connections (0,100000)