Can someone suggest a good book for router and switch configuration in linux. I also want to configure dhcp, dns and other stuff.
firewall distribution solutions (very recomended, if you do not have much experience...): http://www.endian.com and IPCOP firewall (http://sourceforge.net/apps/trac/ipcop/wiki)
Do you mean you are looking for firewall software for Linux?
Vuurmuur is my favourite for that:
It has a easy to use curses interface and a bunch of features that would be needed for a firewall. But that's it, it does not do DNS/DHCP, etc... that you need to do the regular way.
I ran it for years on a few of my servers before switching to PFSense.