Hey there,

New post on ignaonline.com by Sarah Chen:

BGP Communities and Route Filtering on Cisco IOS-XE: A Practical Guide

BGP communities are one of those features that feel optional — until you actually need to manage route policy at scale. In this guide, Sarah breaks down everything you need to know about standard, extended, and large communities on Cisco IOS-XE, with real CLI configs and show command outputs throughout.

What's covered:

• Community types (standard RFC 1997, extended RFC 4360, large RFC 8092) and when to use each
• Enabling send-community per peer and why it's off by default
• Tagging inbound routes by peer type (transit vs. peer vs. customer)
• Community lists and route maps for filtering — blocking transit routes from OSPF redistribution, export filters for peering sessions
• Traffic engineering: upstream-controlled AS path prepending via community, local-pref automation for iBGP
• Remote Triggered Black Hole (RTBH) for DDoS mitigation
• Stripping communities on the way out to avoid leaking internal policy markers
• Verification commands and the most common pitfalls

Read the full guide →

— The ignaonline.com team