Tag Archives: bgp

BGP as-path regular expressions

A regular expression is the character pattern that can be matched against an input string. Regular expressions can be built using letters (A through Z, a through z), numbers (0 through 9) and other keyboard characters, such as the exclamation point (!) or a tilde (~). A regular expression can be a single-character pattern or… Read More »

BGP RIB-Failure

When a Router receives a BGP UPDATE packet that contains Network Layer Reachability Information (NLRI) – this is, a route; the packet is processed in the next order: – Step 1. BGP checks for the NLRI (prefix received) against any BGP inbound filter configured on the Router. – Step 2. If the NLRI is not… Read More »

BGP Aggregate experiment

The BGP aggregate-address can be used to summarise a set of networks into a single prefix. For this post, I just wanted to show the difference between aggregate-address and aggregate-address with summary only. We have below topology. I’m going to summarise prefixes in R1. R1 config hostname R1 ! interface GigabitEthernet0/0 ip address 10.10.10.1 255.255.255.252… Read More »