PGR Spot

Similar to IP Address , BGP also have Public and Private information. Here, we say Public and Private AS instead of Public and Private IP address.  You can refer more at  BGP Public and Private AS . Now, in this article, lets see about BGP Remote Private AS. Consider …

Just like a Public IP Address, ASN (Autonomous System Number) also needs to be unique in the internet. The main reason for this is that EBGP split-horizon (EBGP loop prevention mechanism). EBGP split horizon means, when even the same AS number is seen for any prefix, …

When a particular prefix is learn through both EBGP and IGP (RIP / EIGRP /OSPF), it always the EBGP link as the AD value of EBGP is 20 which is lower as compared to IGP protocols. Let's see it in action with the below topology: From the above topology: - There are…

BGP path selection is based on many attributes, one of the attribute is BGP METRIC (MED), which will be used only when the EBGP traffic is coming from the same AS. I would recommend you to have a look at the  BGP METRIC (MED) - BGP ATTRIBUTE  before reading this a…

BGP uses different types of messages to form neighbor-ship and exchange routes, checking if the remote BGP neighbor is still there and/or notifying the remote side if any errors occur. In-order to do this, BGP uses 4 types of messages: Open message Update message Noti…

By default, BGP will advertise all prefixes to its EBGP neighbors. If you are multi-homed environment (Two ISP's connected),  that you might become a transit AS.    Consider the below topology where R3 is connected to R1 (ISP_1) and R2 (ISP_2) Since, R3 is connect…

By default, BGP will advertise all prefixes to its EBGP neighbors. If you are multi-homed environment (Two ISP's connected),  that you might become a transit AS.    Consider the below topology where R3 is connected to R1 (ISP_1) and R2 (ISP_2) Since, R3 is connect…