Ipswich boss Keane said: "Yes,we're interested. It may be a long shot as he'll have plenty of options."
Ex-England centre-back Campbell, 35, walked out on a £40,000- a-week Notts County deal this week.
West Ham may target a central defender if sought-after Matthew Upson leaves in January.
Boss Zola admitted: "If I was in the need of an experienced player, I'd be thinking about Sol."
