This weekend while working on content updates for CCIE R&S Version 5, I ran into an interesting problem. In order to test some nuances of routing protocol updates and packet fragmentation, I was trying to generate BGP UPDATE messages that would exceed the transit MTU. To do this I manually created a bunch of Loopback interfaces and did a redistribute connected into BGP. When I looked at the packet capture details, I started to realize how many routes I'd actually need in order to fill up the...
Let's say you get a bunch of inexpensive (but a bit outdated) routers (36XX or 72Xx) and some really nice (maybe not so cheap) Cisco switches (e.g. 3550/3560) and you would like to provide a VPLS-like service to your customers. Since VPLS is a service available only on more powerful Cisco platforms, we have to figure a way to simulate Multipoint Ethernet L2 VPN over a packet switching network (PSN) using only "convenient" point-to-point L2 VPN services.