Hello All, My apologies for the incoming wall of text. I'm having an issue with bgpd over a GRE interface. BGP keeps flapping and I suspect it's because the GRE tunnel actually goes down once BGP comes up. Realizing this may be an issue with what's actually being announced, I added host routes to the kernel table for the tunnel endpoints; however that didn't make much of a difference. My setup right now kind of relies on Linux doing the right thing and preferring the longest prefix match to route traffic but I don't think that's what's happening in my case so I'm looking for suggestions on how to proceed. My other, sort of related question, is why does FRR's BGP advertise routes it learns back to the peer it learned them from? Is there a way to stop that behavior? My local endpoint (hostname alpine) is configured like this: auto gre1 iface gre1 inet manual pre-up ip tunnel add gre1 mode gre remote 193.160.88.2 local 73.57.99.182 ttl 255 pre-up ip route add 193.160.88.2/32 via $(ip -4 route list default | awk '{print $3}') pre-up ip addr add 10.64.14.2/24 dev gre1 pre-up ip link set gre1 up post-down ip route del 193.160.88.2/32 post-down ip tunnel del gre1 alpine# show run Building configuration... Current configuration: ! frr version 7.2 frr defaults traditional hostname alpine ! router bgp 65001 neighbor core peer-group neighbor core remote-as 57335 neighbor core bfd neighbor 10.64.14.1 peer-group core ! address-family ipv4 unicast redistribute connected exit-address-family ! line vty ! bfd peer 10.64.14.1 no shutdown ! ! end The remote side (hostname melbidedi1-vrf) is configured like this: auto gre1 iface gre1 inet manual pre-up ip tunnel add gre1 mode gre local 193.160.88.2 remote 73.57.99.182 ttl 255 pre-up ip route add 73.57.99.182/32 via $(ip -4 route list default | awk '{print $3}') pre-up ip addr add 10.64.14.1/24 dev gre1 pre-up ip link set gre1 up post-down ip route del 73.57.99.182/32 post-down ip tunnel del gre1 melbidedi1-vrf# show run Building configuration... Current configuration: ! frr version 7.2 frr defaults traditional hostname melbidedi1 hostname melbidedi1-vrf ! router bgp 57335 neighbor corbe peer-group neighbor corbe remote-as 65001 neighbor corbe bfd neighbor core peer-group neighbor core remote-as 57335 neighbor 10.64.14.2 peer-group corbe neighbor 193.160.88.1 peer-group core ! address-family ipv4 unicast redistribute connected neighbor core next-hop-self exit-address-family ! ip prefix-list AS57335-V4 seq 10 permit 184.203.204.0/22 le 24 ip prefix-list AS57335-V4 seq 15 permit 193.160.88.0/22 le 24 ip prefix-list AS57335-V4 seq 20 permit 45.154.216.0/22 le 24 ip prefix-list AS57335-V4 seq 5 permit 45.132.96.0/22 le 24 ip prefix-list DEFAULT-V4 seq 5 permit 0.0.0.0/0 ip prefix-list INTERNET-V4 seq 5 permit 0.0.0.0/0 le 24 ! line vty ! bfd peer 10.64.14.2 no shutdown ! ! end alpine routing table (as you can see the more specific route is in the kernel routing table): alpine# show ip route Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP, T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP, F - PBR, f - OpenFabric, > - selected route, * - FIB route, q - queued route, r - rejected route K>* 0.0.0.0/0 [0/203] via 73.57.98.1, eth1, src 73.57.99.182, 00:53:51 C>* 10.0.0.0/24 is directly connected, eth2, 00:53:51 C>* 10.64.14.0/24 is directly connected, gre1, 00:29:15 K * 73.57.98.0/23 [0/203] is directly connected, eth1, 00:53:51 C>* 73.57.98.0/23 is directly connected, eth1, 00:53:51 K * 169.254.0.0/16 [0/204] is directly connected, eth2, 00:53:50 C>* 169.254.0.0/16 is directly connected, eth2, 00:53:50 When the tunnel is up, these are the routes being advertised: alpine# show ip bgp neighbors 10.64.14.1 advertised-routes BGP table version is 4151, local router ID is 73.57.99.182, vrf id 0 Default local pref 100, local AS 65001 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath, i internal, r RIB-failure, S Stale, R Removed Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *> 10.0.0.0/24 0.0.0.0 0 32768 ? *> 10.64.14.0/24 0.0.0.0 0 32768 ? *> 73.57.98.0/23 0.0.0.0 0 32768 ? *> 172.16.1.0/24 10.64.14.1 0 57335 ? *> 193.160.88.0/22 10.64.14.1 0 57335 ? *> 193.160.88.0/24 10.64.14.1 0 57335 ? *> 213.183.46.232/29 10.64.14.1 0 57335 ? Routing table on melbidedi1-vrtf: melbidedi1-vrf# show ip route Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP, T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP, F - PBR, f - OpenFabric, > - selected route, * - FIB route, q - queued route, r - rejected route K>* 0.0.0.0/0 [0/0] via 193.160.88.1, eth0, 1d10h18m B>* 10.0.0.0/24 [20/0] via 10.64.14.2, gre1, 00:00:00 C>* 10.64.14.0/24 is directly connected, gre1, 00:23:32 B>* 73.57.98.0/23 [20/0] via 10.64.14.2, gre1, 00:00:00 K>* 73.57.99.182/32 [0/0] via 193.160.88.1, eth0, 00:23:32 C>* 172.16.1.0/24 is directly connected, eth1, 1d10h18m B>* 193.160.88.0/22 [200/0] via 193.160.88.1, eth0, 15:56:10 C>* 193.160.88.0/24 is directly connected, eth0, 1d10h18m B>* 213.183.46.232/29 [200/0] via 193.160.88.1, eth0, 15:56:10 melbidedi1-vrf# show ip bgp neighbors 10.64.14.2 advertised-routes BGP table version is 1146, local router ID is 193.160.88.2, vrf id 0 Default local pref 100, local AS 57335 Status codes: s suppressed, d damped, h history, * valid, > best, = multipath, i internal, r RIB-failure, S Stale, R Removed Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *> 10.0.0.0/24 10.64.14.2 0 65001 ? *> 10.64.14.0/24 0.0.0.0 0 32768 ? *> 73.57.98.0/23 10.64.14.2 0 65001 ? *> 172.16.1.0/24 0.0.0.0 0 32768 ? *> 193.160.88.0/22 0.0.0.0 100 0 ? *> 193.160.88.0/24 0.0.0.0 0 32768 ? *> 213.183.46.232/29 0.0.0.0 100 0 ? Total number of prefixes 7