It may be rare to find an IOS that has its BGP's auto-summary command enabled by default, but I think it is very important to touch on this BGP quirky feature and its impact on how BGP injects routes from IP routing table to its BGP table and how it behaves differently when redistribution or network command is used. Let kick things off by a really simple network topology. Two routers, in the same AS 10 with iBGP neighbor relationship established between the two. R1 has 5 subnets that it will advertise to R2. I will start with no auto-summary configured first, since this is the default in the recent IOS versions. R1: interface Loopback10 ip address 10.10.10.1 255.255.255.0 ! interface Loopback20 ip address 10.10.20.1 255.255.255.0 ! interface Loopback30 ip address
Month: February 2014
L3VPN: Route Leak
Now that we have covered many examples of L3VPN and for different customer deployments, I think this is a good point where we introduce the concept of Route Leaking. Notice in our DIAGRAM, only sites that belong to the same customer could reach each other and this is of course the required end result. But let assume for whatever reason we needed to change this behavior, now Customer C needs to reach Customer D and vice versa. This means, all four sites need to have full connectivity among each other. Simply put, we will need to leak Customer C's VRF routes into Customer D's VRF route table and vice versa. As always, things will get clearer with configuring this part: Just to confirm, at
80’s Groove…WELCOME BACK!!
http://youtu.be/OlEG0Ze4RjI