Hi Thomas, We had a similar discussion on FRR slack, there are some duplicates indeed. Are you planing to test FRR at some point in time?
Cheers, Jeff On Oct 21, 2020, 3:58 PM -0700, Jakob Heitz (jheitz) via NANOG <nanog@nanog.org>, wrote: > Thomas, > > I confirmed your case and took a look at the code. > The outbound duplicate suppression function tries to detect > duplicates without actually storing or recreating the > previously sent update, so it misses some cases. > > Your use case is a good one. We will check to see if we can > detect it without compromising significantly on resource usage. > Thank you for raising the issue. > > Regards, > Jakob. > > -----Original Message----- > Date: Tue, 20 Oct 2020 04:48:37 -0700 > From: Thomas Krenc <tkr...@nps.edu> > > Hi Jakob. > > The simple configuration below allows communities to be forwarded > (send-community-ebgp), but are cleaned at egress (using route-policy and > community-set). > > In the experiment, the router receives announcements with altering > community attributes only, from the internal peer. After the filter is > applied, the router sends duplicates to the external peer. > > Also, In a slightly different setup, the router sends duplicates due to > changes in the next-hop only. > > best regards > Thomas > > --- > > RP/0/0/CPU0:ios(config)#show running-config > Tue Oct 20 02:56:24.230 UTC > Building configuration... > !! IOS XR Configuration 6.0.1 > !! Last configuration change at Tue Oct 20 02:56:02 2020 by cisco > ! > interface MgmtEth0/0/CPU0/0 > ?shutdown > ! > interface GigabitEthernet0/0/0/0 > ?ipv4 address 10.12.0.2 255.255.255.252 > ! > interface GigabitEthernet0/0/0/1 > ?ipv4 address 10.20.0.1 255.255.255.252 > ! > community-set all > ? *:* > end-set > ! > route-policy nofilter > ? pass > end-policy > ! > route-policy egressfilter > ? delete community in all > ? pass > end-policy > ! > router bgp 65002 > ?bgp router-id 10.12.0.2 > ?address-family ipv4 unicast > ! > ?neighbor 10.12.0.1 > ? remote-as 65001 > ? address-family ipv4 unicast > ?? send-community-ebgp > ?? route-policy egressfilter out > ! > ?neighbor 10.20.0.2 > ? remote-as 65002 > ? address-family ipv4 unicast > ! > end > > On 10/17/20 3:59 PM, Jakob Heitz (jheitz) via NANOG wrote: > > IOS-XR has duplicate update suppression logic for EBGP sessions, > > not for IBGP sessions. > > > > If you are using EBGP and seeing a fault in the duplicate update > > suppression logic in IOS-XR, please let me know configs and details > > of the experiment. > > > > Regards, > > Jakob. > > > > -----Original Message----- > > Date: Thu, 15 Oct 2020 18:35:58 -0700 > > From: Thomas Krenc <tkr...@nps.edu> > > > > Dear NANOG, > > > > As a team of researchers from NPS and TU Berlin, we are investigating > > the impact of BGP community attributes on the update behavior between ASes. > > > > We find that when a route is associated with multiple distinct community > > attributes it does not only lead to multiple announcement at the tagging > > AS, but also at neighboring ASes, if communities are not filtered > > properly. This behavior is wide-spread. > > > > In order to better understand our observations, we have performed a > > series of laboratory experiments using Cisco IOS, Junos OS, as well as > > the BIRD daemon. > > > > We find that - by default - all tested routers generate announcements > > with changing community attributes, even when other attributes do not > > change. In addition, when communities are filtered at egress, Cisco und > > BIRD send duplicate announcements (Juniper does not). > > > > Since our findings are limited to observations in public data as well as > > few router implementations, we would like to share our research and > > kindly ask you to have a look at: > > > > ??? https://www.cmand.org/communityexploration/ > > > > There, we provide some resources documenting our research, as well as > > open questions. We greatly appreciate any feedback and insights you can > > offer. Also, please don't hesitate to contact us directly: > > > > ??? communityexploration AT cmand DOT org > > > > best regards > > > > Thomas Krenc > > Postdoctoral Researcher > > Naval Postgraduate School