Hi Andre, Replaces were supported a long time ago [0]. Did you have a chance to check on newer vpp?
[0] - https://gerrit.fd.io/r/c/vpp/+/38854 On Wed, 13 Aug 2025 at 00:41, Andre Nathan via lists.fd.io <andre= digirati.com...@lists.fd.io> wrote: > When inspecting captured netlink messages on wireshark, I noticed that > first a “route add” message is sent with flags CREATE and EXCL with my > other router as the gateway. This is the route from the iBGP session which > ends up in the VPP FIB. Then a second “route add” message is sent with > flags CREATE and REPLACE, with the uplink peer router as the gateway. This > route is not installed in the VPP FIB, though it is in the kernel routing > table, as I showed in the previous email. > > I’m not sure if LCP is simply not getting the second message or if it gets > it but doesn’t install the route due to some error. > > Thanks, > Andre > > > > Em 11 de ago. de 2025, à(s) 16:24, Andre Nathan via lists.fd.io <andre= > digirati.com...@lists.fd.io> escreveu: > > > > Hi > > > >> On 8/8/25 3:14 PM, Matthew Smith via lists.fd.io wrote: > >> You could try adding del-dynamic-on-link-down to the linux-cp section > of your startup.conf and see if that helps. > > > > I've tried this parameter, but it didn't make a difference when bringing > the iBGP session down. > > > > Now that I'm inspecting this more closely, I've found some strange > behavior where the VPP routes don't match the ones installed by Bird. > > > > In this case, I've started bird with the uplink BGP session enabled, and > afterwards started the iBGP session. I've noticed the VPP FIB has ~24k > routes pointing to my other router, that is, learned via the iBGP session. > This is weird because routes via the other router should only be used in > case the BGP session with the uplink peer goes down, as they by definition > have one extra hop, and are therefore "worse". > > > > I've checked that bird is indeed selecting the uplink route as the > preferred one. One example: > > > > # birdc show route for 45.181.63.0/24 > > BIRD 2.16.1 ready. > > Table master4: > > 45.181.63.0/24 unicast [uplink_ipv4 17:44:31.966] * (100) [AS269170i] > > via x.y.z.w on uplink1 > > unicast [ibgp_ipv4 17:44:31.609] (100) [AS269170i] > > via a.b.c.d on external > > > > The kernel route is in agreement: > > > > # ip route show 45.181.63.0/24 > > 45.181.63.0/24 via x.y.z.w dev uplink1 proto bird metric 32 > > > > But the route in VPP is through my other router (a.b.c.d): > > > > # vppctl show ip fib 45.181.63.0/24 > > ipv4-VRF:0, fib_index:0, flow hash:[src dst sport dport proto flowlabel > ] epoch:0 flags:none locks:[adjacency:1, default-route:1, lcp-rt:1, ] > > 45.181.63.0/24 fib:0 index:18181 locks:2 > > lcp-rt-dynamic refs:1 src-flags:added,contributing,active, > > path-list:[77] locks:49272 flags:shared,popular, uPRF-list:69 len:1 > itfs:[7, ] > > path:[103] pl-index:77 ip4 weight=1 pref=32 attached-nexthop: > oper-flags:resolved, > > a.b.c.d BondEthernet0 > > [@0]: ipv4 via a.b.c.d BondEthernet0: mtu:1500 next:8 flags:[] > 12b9c288223f3cfdfe9ec4e40800 > > > > forwarding: unicast-ip4-chain > > [@0]: dpo-load-balance: [proto:ip4 index:18182 buckets:1 uRPF:69 > to:[0:0]] > > [0] [@5]: ipv4 via a.b.c.d BondEthernet0: mtu:1500 next:8 flags:[] > 12b9c288223f3cfdfe9ec4e40800 > > ipv4-VRF:180, fib_index:1, flow hash:[src dst sport dport proto > flowlabel ] epoch:0 flags:none locks:[lcp-rt:1, ] > > 0.0.0.0/0 fib:1 index:49 locks:2 > > default-route refs:1 entry-flags:drop, > src-flags:added,contributing,active, > > path-list:[66] locks:2 flags:drop, uPRF-list:62 len:0 itfs:[] > > path:[92] pl-index:66 ip4 weight=1 pref=0 special: cfg-flags:drop, > > [@0]: dpo-drop ip4 > > > > forwarding: unicast-ip4-chain > > [@0]: dpo-load-balance: [proto:ip4 index:50 buckets:1 uRPF:62 to:[0:0]] > > [0] [@0]: dpo-drop ip4 > > > > > > > > I don't really know how to explain that. > > > > > > > > > > > > > > > > -- Best regards Stanislav Zaikin
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