Tag Archives: bgp

Arista – dealing with inactive routes in BGP

In EOS, BGP implementation normally considers only active routes in RIB for advertisement to its peers. In certain deployments, IGP protocol like OSPF may carry same set of prefixes as BGP (especially if we use OSPF to form iBGP). In addition, routes from OSPF and BGP may be mutually redistributed. As a result, when local… Read More »

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… Read More »