From e69c3b60729521020c0077c2f6d858825e47bd15 Mon Sep 17 00:00:00 2001 From: Simon Marsh Date: Sun, 13 Sep 2020 00:15:31 +0100 Subject: [PATCH] add ghost route protection --- pages/01.home/bgp-communities/default.md | 21 +++++++++++++++++++++ pages/01.home/maintenance-log/default.md | 3 +++ 2 files changed, 24 insertions(+) diff --git a/pages/01.home/bgp-communities/default.md b/pages/01.home/bgp-communities/default.md index 77ae3de..ec2fd44 100755 --- a/pages/01.home/bgp-communities/default.md +++ b/pages/01.home/bgp-communities/default.md @@ -52,3 +52,24 @@ burble.dn42 implements [large BGP communities](http://largebgpcommunities.net/), | ( 4242422601 : 140 : _DN42 region_ )   | Route learned in this DN42 region |   +### Ghost Route Protection + +In a large network like burble.dn42 it can take some time for route updates +to be distributed and for the network to settle following changes. This can +be particularly noticeable when routes are deleted as it can create a +cascade of ghost updates, each with an increasing internal path length as +the route removal spreads across the network. + +To protect against ghost routes, a community is used to track how many internal +hops a route has. In a fully meshed network like burble.dn42, a genuine route should +never have more than two internal hops, so an export filter is used to prevent +distribution of longer paths. + +|Community  |Description| +|:---|:---| +| ( 4242422601 : 100 : 1 )   | Added on first internal re-distribution | +| ( 4242422601 : 100 : 2 )   | Added on second re-distribution and prevents further re-distribution within burble.dn42 | +  + +The ( 4242422601 : 100 : x ) communities are not exported to peers. + diff --git a/pages/01.home/maintenance-log/default.md b/pages/01.home/maintenance-log/default.md index 680f3cc..2a50133 100755 --- a/pages/01.home/maintenance-log/default.md +++ b/pages/01.home/maintenance-log/default.md @@ -15,6 +15,9 @@ A log of changes to the burble.dn42 network. uk-lon1 has been upgraded. If you are peered on this node, please update your IP address accordingly. +burble.dn42 now includes some limited protection against ghost route updates. +See the [communities](/home/bgp-communities) page for more details. + #### 9th September 2020 uk-lon1 will be upgraded this weekend (12/13th