This happened over a decade ago when I was a budding L1 engineer, monitoring network infrastructure of a bank. This post is recollection of a memory when my team-lead (a great mentor) at the time, put me through a challenging exercise to meet a seemingly simple customer requirement. Existing Topology We had this typical topology […]
A scenario came up when a colleague was working on a project where his router was peering with a 3rd party router over eBGP. The router was performing aggregation for 10.x.x.x subnets, summary-only as 10.x/16. We know that BGP will generate a null0 anchor route automatically for the summary address. Now a situation occurred where […]
This topic is about BGP’s ability to prefer another router (kinda de-prefer, actually). The following diagram will make it clear. In this situation, it may be a better choice to traverse from R1 to R2 via the point-to-point link instead of going over the ISP Cloud. Here R1 and R2 are eBGP peers only. The […]
Lately, I have been struggling to understand the logic behind route-map and its functioning when used along with a prefix-list in order to filter prefixes. Basically configurations where the permit/deny of prefix-list couples with permit/deny of route-map. So I decided to lab it out in GNS3 – only allow 172.1.1.0/24 to pass through; filter everything […]
