Foundry Networks ( FDRY) dropped 7% late Thursday after guiding Wall Street toward a lower-than-expected first-quarter profit. For its quarter ended Dec. 31, the San Jose, Calif., networking company earned $17 million, or 12 cents a share, down from the year-ago $24 million, or 17 cents a share. Sales fell to $105 million from $111 million a year earlier. The fourth-quarter profit met Wall Street estimates, but revenue was a shade light of the $107 million consensus target. The company said it expects to post a first-quarter profit of 8 cents to 12 cents a share on revenue of $100 million to $110 million. Those figures skew toward the low end of guidance. A Thomson First Call estimate has the company earning 12 cents a share for the first quarter on sales of $107 million. Foundry slipped 81 cents in postclose action to $10.10.