I have heard that having sites with the same IP address linking to each other does not help your PR at all. What if the sites have different IP addresses, but are on the same physical server?
There will be some effect since every backlink counts in terms of any rankings. But I don't think that there will be very high value for such a backlink. Better to build links from various IPs.
its better to have different ips with different server. I think not to try something which is harmful to you site as well as the google crawler or bot
Well that's what I'm wondering... I can give each site a different IP address, but they will still be on the same physical server. So I guess my question is: Does Google look at the just IP address of the website, or do they look at the nameserver info to see if it's on the same server?
Same C class IP's in most cases = some sort of Google penalty eventually. I have even seen a network of about 100 blogs each on a seperate C class IP on the same server get totally deindexed. Don't do it it's not worth the risk if these are your money sites.