July 8, 2010

Dynamic Multipoint VPN - DMVPN

One of the most interesting feature of DMVPN as far as my personal opinion goes is its extended support for VRF on MPLS networks. Remember, VRF allows multiple instance of routing tables to co-exist on the same router at the same time. Having said that, DMVPN helps scalling out tradional IPSEC hub-and-spoke VPN configuration by setting permanent and temporary connections, respectively from the spoke routers to the hub router and between the spoker routers as needed. ... Read more

January 20, 2010

QinQ Vlan tagging and S-Vlans

Pre-requiste: Understanding of the 802.1Q Protocol The purpose of this post is to shed a light on how QinQ Vlan takes place in a bridged network environment. Before continuing, it is important to keep in mind that 802.1QinQ or 802.1ad isn’t a defined protocol in itself but a mere amendment of the already existing 802.1Q protocol. Having said that, in a nutshell where a single frame can hold a maximum of 4096 tags, QinQ extends the number of maximum tags to 16777216 tags, thus allowing switches to freely manipulate the tags of a single packet. ... Read more

October 17, 2009

PPP - the unnumbered IP command

I am not going to go over in details on the hoods of PPP (another post will be written for this purpose). A deep understanding of Point-to-Point WAN networks isn’t required as we will barely scratch that surface when dealing with the “unnumbered IP command”. So what is the unnumbered IP command? The unnumbered IP command enables you to enable IP routing/processing on an interface by assigning it an IP already in used of another interface. That is to say, the unnumbered IP command enables you to have 2 interfaces, a multi-access interface and a point to point interface (often a serial port) to share the same IP address. –> Now why would you do that? Simple, to save IPs and avoid in many cases to use VLSM if not needed. ... Read more