MTV Networks (NYSE: VIA) is readying Tribes, an online ad network tied to its various cable channels, Mediaweek reports. Tribes will pull in outside sites to establish ad sales and content syndication for MTV, VH1, Spike TV and CMT over the next several weeks. At some point after the new year, Comedy Central will get the Tribes treatment as well. Tribes is modeled on the ParentsConnect ad net, which MTVN’s Nickelodeon set up in February, with less than a dozen blogs and sites related to children’s entertainment. The company tells Mediaweek that ParentsConnect now has 46 sites, with more to come. At launch, Tribes is connected with Echo, which has is comprised of several fan sites focusing on particular artists like Alicia Keys and Kanye West. Each Tribe is made up of people who visit the networks’ Website, and can be targeted elsewhere. In this case, the “MTV Generation Tribe” is supposedly made up of that hard-to-reach youth demographic that is interested in music, movies, videogames, sports, and sneakers. According to MTV Networks, each of its online properties has users that are staggeringly similar and can be targeted more effectively than trying to decipher groups across a wide array of networks based on age or gender. Once the Tribe is formed from users, the networks will sell advertising inventory and packages using demo-targeting, geo-targeting, day-parting and contextual targeting that it believes will capture the right audience for the right advertiser. The MTV Tribe ad-network, which is anchored by MTV.com, launched today with Pepsi as its hallmark sponsor. CMT, Spike, and VH1 Tribes will be launching later this month and the Comedy Central Tribe will launch during the first quarter of 2009.