The after-hours markets saw a quiet, mixed trading session tonight, epitomized by the fact that

Cisco

(CSCO) - Get Report

, the largest volume trader on both

Island

and

Instinet,

was largely unchanged through the evening session and was lately down just 20 cents, or 1%, on both networks.

An

upbeat note from

Morgan Stanley Dean Witter

this morning sent the networking sector soaring into the green, and Cisco refused to miss out, posting heady gains of 12.4% for the day.

The rest of the post-market trading session looked like a tomato patch -- i.e., a steady mix of red and green -- as investors skimmed profits from some common four-lettered folk and pumped the money back into others. Four straight days of gains on the tech-heavy

Nasdaq Composite Index

seemed to have set the stage for a slight sell-off tonight as investors looked to pocket a little green.

The big percentage loser tonight was biotech company

Genzyme General

(GENZ)

, which announced after market close tonight that it would issue $500 million in convertible debt. The stock fell 2.6% during the regular trading day, and then fell by a sharper 4.2%, or $4.56, to $103.60 on Instinet. Genzyme was down 4.3% to $103.53 on Island trading.

Big name tech players

JDS Uniphase

(JDSU)

and

Veritas Software

(VRTS) - Get Report

also slipped in share price in after-hours trading. Veritas, a victim of post-market profit-taking, fell by 21 cents to $71.95 on Instinet after a heady 9.3% gain during the day. JDSU fell into the same category, riding high on a 7.9% daytime gains only to fall 35 cents to $23.50 in the after-hours.

On the flip side, investors seemed to want to keep riding

Sun Microsystems

(SUNW) - Get Report

higher after its 7.7% regular hour gains. Sun posted a rise of 0.8% on Instinet, climbing to $20.60. Following Sun higher was

Sonus Networks

(SONS)

.

Sonus rose during regular trading after announcing a sales and marketing alliance with

Juniper Networks

(JNPR) - Get Report

. Sonus rose 10.3% during regular market trading, and continued up another 0.2% to $30.45 on Instinet. Juniper fell 1.1% to $64.41 on Instinet, and by a slightly lesser 0.9% on Island.

Software maker

Oracle

(ORCL) - Get Report

picked up a strong 7% during the daytime, and then fell 16 cents to $17.01 in the after-hours market on Instinet.

Trading remained mild and mixed between a handful of other tech names on Instinet, keeping the net change overall in the after-hours close to zero.

A couple smaller names popped up on Island trading with dramatic moves. Penny stock

Ibeam Broadcasting

(IBEM)

was the number two volume trader on Island, rising 2 cents to 50 cents. And

Buy.com

(BUYX)

fell 31.5% to just 50 cents on Island after posting a pro forma per share loss of eight cents tonight, vs. a 23 cents a share loss in the year-ago period. The company also said that it sees revenues decreasing in the next quarter.

This information is provided by Instinet, a wholly owned subsidiary of Reuters (RTRSY) . For further information, please contact Instinet at www.instinet.com.

Island ECN offers trading, mainly in Nasdaq-listed stocks, from 7 a.m. to 8 p.m. EST.

Confused?

TheStreet.com

explains how the rules change when the sun goes down in Investing Basics: Night Owl, a section devoted to after-hours trading.