Verify end to end
Check the network as a whole, from the inside out:
- Every router has a full iBGP mesh. Each edge shows two internal neighbors plus its external one.
- The edges announce only the aggregate. The /25 that core1 originates stays inside: the export maps match
OUR-PREFIXESexactly, so neither the LAN prefix nor the loopbacks and link addresses ever leave the AS. - core1 chooses the right exit for each destination. Local preference set on the edges travels with the route over iBGP, so core1 makes the same IX-first choice R1 did in the previous lesson, without any policy of its own.
- Traffic follows that choice. A traceroute from the LAN host should show core1, then the edge that owns the exit, then the destination.
Hop 2 of each traceroute is the edge's address on its link to core1 (the address that sent the ICMP reply), not its loopback. That's normal: a router replies from the interface the probe arrived on.
vyos@edge1:~$ show ip bgp summary
IPv4 Unicast Summary:
BGP router identifier 198.51.100.242, local AS number 64500 VRF default vrf-id 0
BGP table version 6
RIB entries 5, using 800 bytes of memory
Peers 3, using 90 KiB of memory
Peer groups 1, using 72 bytes of memory
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd PfxSnt Desc
198.51.100.241 4 64500 5 6 6 0 0 00:01:05 2 2 core1
198.51.100.243 4 64500 45 45 6 0 0 00:40:39 1 2 edge2
203.0.113.0 4 64496 29 27 6 0 0 00:23:36 2 1 UPSTREAM transit
Total number of neighbors 3
vyos@edge1:~$ show ip bgp neighbors 203.0.113.0 advertised-routes
BGP table version is 6, local router ID is 198.51.100.242, vrf id 0
Default local pref 100, local AS 64500
Status codes: s suppressed, d damped, h history, u unsorted, * 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
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
*>i 198.51.100.0/24 0.0.0.0 0 i
Total number of prefixes 1, total number of paths 1- Lines 11–13: Two iBGP neighbors (descriptions truncated) and the upstream.
- Line 26: Only the aggregate goes to the upstream; not the /25, loopbacks or links. The
ishows it was learnt over iBGP from core1.
vyos@edge2:~$ show ip bgp neighbors 192.0.2.1 advertised-routes
BGP table version is 5, local router ID is 198.51.100.243, vrf id 0
Default local pref 100, local AS 64500
Status codes: s suppressed, d damped, h history, u unsorted, * 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
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
*>i 198.51.100.0/24 0.0.0.0 0 i
Total number of prefixes 1, total number of paths 1- Line 10: The same single prefix on the IX side.
root@host:~# traceroute -n 203.0.113.65
traceroute to 203.0.113.65 (203.0.113.65), 30 hops max, 60 byte packets
1 198.51.100.1 3.209 ms 3.447 ms 3.521 ms
2 198.51.100.226 6.844 ms 6.998 ms 7.269 ms
3 203.0.113.65 13.109 ms 13.114 ms 13.113 ms
root@host:~# traceroute -n 203.0.113.130
traceroute to 203.0.113.130 (203.0.113.130), 30 hops max, 60 byte packets
1 198.51.100.1 0.293 ms 0.263 ms 0.254 ms
2 198.51.100.224 3.353 ms 3.516 ms 3.520 ms
3 203.0.113.130 3.935 ms 4.188 ms 4.189 ms- Line 3: core1, the host's gateway.
- Lines 4–5: edge2 (its link address towards core1), then the IX member.
- Lines 9–10: edge1, then the upstream.