BGP · Labs

BGP Professional Lab

Integrate transport, underlay, confederation, address families and focused policy in one staged practice network.

Topology and address plan

R1 connects the regional network to ISP/R10. R2/R3 form AS65023. R4–R7 form confederation 65467, with member AS65045 on R4/R5 and 65067 on R6/R7. R8 forwards transport only; R9 uses private four-byte AS4200000009. All addresses and assignments here are an isolated original lab plan.

Lab topologyPhysical links

Solid lines are physical links. Endpoint labels are the last octets of 192.0.2.x/30, first router then second router in the address table. Loopback0 is 10.255.0.N/32 on RN. Logical BGP peers are listed in the configurations.

Link	First endpoint	Second endpoint
R10–R1	GigabitEthernet1 192.0.2.1/30	GigabitEthernet1 192.0.2.2/30
R1–R4	GigabitEthernet2 192.0.2.5/30	GigabitEthernet1 192.0.2.6/30
R1–R2	GigabitEthernet3 192.0.2.9/30	GigabitEthernet1 192.0.2.10/30
R1–R3	GigabitEthernet4 192.0.2.13/30	GigabitEthernet1 192.0.2.14/30
R2–R3	GigabitEthernet2 192.0.2.17/30	GigabitEthernet2 192.0.2.18/30
R2–R4	GigabitEthernet3 192.0.2.21/30	GigabitEthernet2 192.0.2.22/30
R3–R5	GigabitEthernet3 192.0.2.25/30	GigabitEthernet1 192.0.2.26/30
R4–R5	GigabitEthernet3 192.0.2.29/30	GigabitEthernet2 192.0.2.30/30
R4–R6	GigabitEthernet4 192.0.2.33/30	GigabitEthernet1 192.0.2.34/30
R5–R7	GigabitEthernet3 192.0.2.37/30	GigabitEthernet1 192.0.2.38/30
R6–R7	GigabitEthernet2 192.0.2.41/30	GigabitEthernet2 192.0.2.42/30
R5–R8	GigabitEthernet4 192.0.2.45/30	GigabitEthernet1 192.0.2.46/30
R8–R9	GigabitEthernet2 192.0.2.49/30	GigabitEthernet1 192.0.2.50/30

Outputs are illustrative, not recorded router results. Each lab starts from its own baseline. Configuration and feature support vary by image and release; platform-specific examples identify their prerequisites.

The long R1–R4 link uses an elbow above the diagram to keep it clear of R2. The table gives every physical interface address; logical sessions and the tunnel are in the solved configurations.

Start without revealing the solution

Open startup interface configurations. Load each device’s block separately. No router images, credentials or proprietary software are included. The startup file intentionally contains no BGP, OSPF, tunnel or routing-policy solution.

Recommended checkpoints: interfaces, underlay, BGP sessions, IPv6 exchange, then one policy experiment at a time. Save a copy before each fault or policy change. The completed core solution is collapsed below so you can attempt the tasks first.

Task list

Area	Required result
Underlay	Build OSPF in AS65023 and across the confederation; resolve all internal loopbacks.
BGP transport	Use loopbacks for internal sessions and direct addresses externally, except the tunneled R5–R9 session.
Confederation	Use member 65045 for R4/R5 and 65067 for R6/R7; present 65467 externally.
Tunnel	Carry R5–R9 data across BGP-free R8 with GRE, avoiding recursive tunnel endpoints.
Address families	Exchange IPv6 with the ISP on IPv6 TCP, and carry IPv6 over IPv4 TCP into AS65023 only.
Origination	Advertise each BGP router’s Loopback0 plus the four ISP documentation /26s, using exact statements.
Weight	On R4, prefer the AS65023 route for 198.51.100.0/26 only.
Local preference	Inside AS65023, prefer R2’s exit for 198.51.100.64/26 only.
Path scope	Tag 198.51.100.128/26 No Advertise on export from R1 to R2/R3/R4.
Export safety	Allow only regional loopback /32s toward the ISP; do not offer transit for received ISP routes.
Filtering	On R9, temporarily reject the first /26; demonstrate removal and restoration without changing its ASN.
Convergence	Remove one redundant external link, observe an alternate, restore it, and distinguish expected route changes from measured outage time.

For an optional historical exercise, inspect the Auto-summary lesson rather than enabling classful behavior in this addressed lab. For aggregation, use current summaries without AS_SET. The focused lessons provide additional dampening, peer-group, Add-Path and PIC experiments with their own prerequisites.

Core solution and transport explanation

Complete baseline configurations

R10

hostname R10
ip cef
ipv6 unicast-routing
interface Loopback0
 ipv6 address 2001:db8:ffff::10/128
 ip address 10.255.0.10 255.255.255.255
exit
interface Loopback11
 ip address 198.51.100.1 255.255.255.192
exit
interface Loopback12
 ip address 198.51.100.65 255.255.255.192
exit
interface Loopback13
 ip address 198.51.100.129 255.255.255.192
exit
interface Loopback14
 ip address 198.51.100.193 255.255.255.192
exit
interface GigabitEthernet1
 ipv6 address 2001:db8:0:10::2/64
 ip address 192.0.2.1 255.255.255.252
 no shutdown
exit
router bgp 64496
 bgp router-id 10.255.0.10
 no bgp default ipv4-unicast
 neighbor 192.0.2.2 remote-as 65001
 neighbor 2001:db8:0:10::1 remote-as 65001
 address-family ipv4 unicast
  no auto-summary
  neighbor 192.0.2.2 activate
  network 10.255.0.10 mask 255.255.255.255
  network 198.51.100.0 mask 255.255.255.192
  network 198.51.100.64 mask 255.255.255.192
  network 198.51.100.128 mask 255.255.255.192
  network 198.51.100.192 mask 255.255.255.192
 exit-address-family
 address-family ipv6 unicast
  neighbor 2001:db8:0:10::1 activate
  network 2001:db8:ffff::10/128
 exit-address-family
end

R1

hostname R1
ip cef
ipv6 unicast-routing
interface Loopback0
 ipv6 address 2001:db8:ffff::1/128
 ip address 10.255.0.1 255.255.255.255
exit
interface GigabitEthernet1
 ipv6 address 2001:db8:0:10::1/64
 ip address 192.0.2.2 255.255.255.252
 no shutdown
exit
interface GigabitEthernet2
 ip address 192.0.2.5 255.255.255.252
 no shutdown
exit
interface GigabitEthernet3
 ipv6 address 2001:db8:0:12::1/64
 ip address 192.0.2.9 255.255.255.252
 no shutdown
exit
interface GigabitEthernet4
 ipv6 address 2001:db8:0:13::1/64
 ip address 192.0.2.13 255.255.255.252
 no shutdown
exit
router bgp 65001
 bgp router-id 10.255.0.1
 no bgp default ipv4-unicast
 neighbor 192.0.2.1 remote-as 64496
 neighbor 192.0.2.10 remote-as 65023
 neighbor 192.0.2.14 remote-as 65023
 neighbor 192.0.2.6 remote-as 65467
 neighbor 2001:db8:0:10::2 remote-as 64496
 address-family ipv4 unicast
  no auto-summary
  neighbor 192.0.2.1 activate
  neighbor 192.0.2.10 activate
  neighbor 192.0.2.14 activate
  neighbor 192.0.2.6 activate
  network 10.255.0.1 mask 255.255.255.255
 exit-address-family
 address-family ipv6 unicast
  neighbor 2001:db8:0:10::2 activate
  network 2001:db8:ffff::1/128
 exit-address-family
router bgp 65001
 address-family ipv6 unicast
  neighbor 192.0.2.10 activate
  neighbor 192.0.2.10 route-map V6-12-1 out
 exit-address-family
route-map V6-12-1 permit 10
 set ipv6 next-hop 2001:db8:0:12::1
exit
router bgp 65001
 address-family ipv6 unicast
  neighbor 192.0.2.14 activate
  neighbor 192.0.2.14 route-map V6-13-1 out
 exit-address-family
route-map V6-13-1 permit 10
 set ipv6 next-hop 2001:db8:0:13::1
exit
end

R2

hostname R2
ip cef
ipv6 unicast-routing
interface Loopback0
 ipv6 address 2001:db8:ffff::2/128
 ip address 10.255.0.2 255.255.255.255
exit
interface GigabitEthernet1
 ipv6 address 2001:db8:0:12::2/64
 ip address 192.0.2.10 255.255.255.252
 no shutdown
exit
interface GigabitEthernet2
 ip address 192.0.2.17 255.255.255.252
 no shutdown
exit
interface GigabitEthernet3
 ip address 192.0.2.21 255.255.255.252
 no shutdown
exit
router ospf 1
 router-id 10.255.0.2
 network 10.255.0.2 0.0.0.0 area 0
 passive-interface Loopback0
 network 192.0.2.17 0.0.0.0 area 0
exit
router bgp 65023
 bgp router-id 10.255.0.2
 no bgp default ipv4-unicast
 neighbor 192.0.2.9 remote-as 65001
 neighbor 10.255.0.3 remote-as 65023
 neighbor 10.255.0.3 update-source Loopback0
 neighbor 192.0.2.22 remote-as 65467
 address-family ipv4 unicast
  no auto-summary
  neighbor 192.0.2.9 activate
  neighbor 10.255.0.3 activate
  neighbor 10.255.0.3 next-hop-self
  neighbor 192.0.2.22 activate
  network 10.255.0.2 mask 255.255.255.255
 exit-address-family
router bgp 65023
 address-family ipv6 unicast
  neighbor 192.0.2.9 activate
  neighbor 192.0.2.9 route-map V6-12-2 out
 exit-address-family
route-map V6-12-2 permit 10
 set ipv6 next-hop 2001:db8:0:12::2
exit
end

R3

hostname R3
ip cef
ipv6 unicast-routing
interface Loopback0
 ipv6 address 2001:db8:ffff::3/128
 ip address 10.255.0.3 255.255.255.255
exit
interface GigabitEthernet1
 ipv6 address 2001:db8:0:13::2/64
 ip address 192.0.2.14 255.255.255.252
 no shutdown
exit
interface GigabitEthernet2
 ip address 192.0.2.18 255.255.255.252
 no shutdown
exit
interface GigabitEthernet3
 ip address 192.0.2.25 255.255.255.252
 no shutdown
exit
router ospf 1
 router-id 10.255.0.3
 network 10.255.0.3 0.0.0.0 area 0
 passive-interface Loopback0
 network 192.0.2.18 0.0.0.0 area 0
exit
router bgp 65023
 bgp router-id 10.255.0.3
 no bgp default ipv4-unicast
 neighbor 192.0.2.13 remote-as 65001
 neighbor 10.255.0.2 remote-as 65023
 neighbor 10.255.0.2 update-source Loopback0
 neighbor 192.0.2.26 remote-as 65467
 address-family ipv4 unicast
  no auto-summary
  neighbor 192.0.2.13 activate
  neighbor 10.255.0.2 activate
  neighbor 10.255.0.2 next-hop-self
  neighbor 192.0.2.26 activate
  network 10.255.0.3 mask 255.255.255.255
 exit-address-family
router bgp 65023
 address-family ipv6 unicast
  neighbor 192.0.2.13 activate
  neighbor 192.0.2.13 route-map V6-13-3 out
 exit-address-family
route-map V6-13-3 permit 10
 set ipv6 next-hop 2001:db8:0:13::2
exit
end

R4

hostname R4
ip cef
interface Loopback0
 ip address 10.255.0.4 255.255.255.255
exit
interface GigabitEthernet1
 ip address 192.0.2.6 255.255.255.252
 no shutdown
exit
interface GigabitEthernet2
 ip address 192.0.2.22 255.255.255.252
 no shutdown
exit
interface GigabitEthernet3
 ip address 192.0.2.29 255.255.255.252
 no shutdown
exit
interface GigabitEthernet4
 ip address 192.0.2.33 255.255.255.252
 no shutdown
exit
router ospf 1
 router-id 10.255.0.4
 network 10.255.0.4 0.0.0.0 area 0
 passive-interface Loopback0
 network 192.0.2.29 0.0.0.0 area 0
 network 192.0.2.33 0.0.0.0 area 0
exit
router bgp 65045
 bgp router-id 10.255.0.4
 bgp confederation identifier 65467
 bgp confederation peers 65067
 no bgp default ipv4-unicast
 neighbor 192.0.2.5 remote-as 65001
 neighbor 192.0.2.21 remote-as 65023
 neighbor 10.255.0.5 remote-as 65045
 neighbor 10.255.0.5 update-source Loopback0
 neighbor 10.255.0.6 remote-as 65067
 neighbor 10.255.0.6 update-source Loopback0
 neighbor 10.255.0.6 ebgp-multihop 2
 address-family ipv4 unicast
  no auto-summary
  neighbor 192.0.2.5 activate
  neighbor 192.0.2.21 activate
  neighbor 10.255.0.5 activate
  neighbor 10.255.0.5 next-hop-self
  neighbor 10.255.0.6 activate
  neighbor 10.255.0.6 next-hop-self
  network 10.255.0.4 mask 255.255.255.255
 exit-address-family
end

R5

hostname R5
ip cef
interface Loopback0
 ip address 10.255.0.5 255.255.255.255
exit
interface GigabitEthernet1
 ip address 192.0.2.26 255.255.255.252
 no shutdown
exit
interface GigabitEthernet2
 ip address 192.0.2.30 255.255.255.252
 no shutdown
exit
interface GigabitEthernet3
 ip address 192.0.2.37 255.255.255.252
 no shutdown
exit
interface GigabitEthernet4
 ip address 192.0.2.45 255.255.255.252
 no shutdown
exit
ip route 192.0.2.50 255.255.255.255 192.0.2.46
ip route 10.255.0.9 255.255.255.255 Tunnel0
interface Tunnel0
 ip address 192.0.2.201 255.255.255.252
 tunnel source GigabitEthernet4
 tunnel destination 192.0.2.50
exit
router ospf 1
 router-id 10.255.0.5
 network 10.255.0.5 0.0.0.0 area 0
 passive-interface Loopback0
 network 192.0.2.30 0.0.0.0 area 0
 network 192.0.2.37 0.0.0.0 area 0
exit
router bgp 65045
 bgp router-id 10.255.0.5
 bgp confederation identifier 65467
 bgp confederation peers 65067
 no bgp default ipv4-unicast
 neighbor 192.0.2.25 remote-as 65023
 neighbor 10.255.0.4 remote-as 65045
 neighbor 10.255.0.4 update-source Loopback0
 neighbor 10.255.0.7 remote-as 65067
 neighbor 10.255.0.7 update-source Loopback0
 neighbor 10.255.0.7 ebgp-multihop 2
 neighbor 10.255.0.9 remote-as 4200000009
 neighbor 10.255.0.9 update-source Loopback0
 neighbor 10.255.0.9 ebgp-multihop 2
 address-family ipv4 unicast
  no auto-summary
  neighbor 192.0.2.25 activate
  neighbor 10.255.0.4 activate
  neighbor 10.255.0.4 next-hop-self
  neighbor 10.255.0.7 activate
  neighbor 10.255.0.7 next-hop-self
  neighbor 10.255.0.9 activate
  neighbor 10.255.0.9 next-hop-self
  network 10.255.0.5 mask 255.255.255.255
 exit-address-family
end

R6

hostname R6
ip cef
interface Loopback0
 ip address 10.255.0.6 255.255.255.255
exit
interface GigabitEthernet1
 ip address 192.0.2.34 255.255.255.252
 no shutdown
exit
interface GigabitEthernet2
 ip address 192.0.2.41 255.255.255.252
 no shutdown
exit
router ospf 1
 router-id 10.255.0.6
 network 10.255.0.6 0.0.0.0 area 0
 passive-interface Loopback0
 network 192.0.2.34 0.0.0.0 area 0
 network 192.0.2.41 0.0.0.0 area 0
exit
router bgp 65067
 bgp router-id 10.255.0.6
 bgp confederation identifier 65467
 bgp confederation peers 65045
 no bgp default ipv4-unicast
 neighbor 10.255.0.4 remote-as 65045
 neighbor 10.255.0.4 update-source Loopback0
 neighbor 10.255.0.4 ebgp-multihop 2
 neighbor 10.255.0.7 remote-as 65067
 neighbor 10.255.0.7 update-source Loopback0
 address-family ipv4 unicast
  no auto-summary
  neighbor 10.255.0.4 activate
  neighbor 10.255.0.4 next-hop-self
  neighbor 10.255.0.7 activate
  neighbor 10.255.0.7 next-hop-self
  network 10.255.0.6 mask 255.255.255.255
 exit-address-family
end

R7

hostname R7
ip cef
interface Loopback0
 ip address 10.255.0.7 255.255.255.255
exit
interface GigabitEthernet1
 ip address 192.0.2.38 255.255.255.252
 no shutdown
exit
interface GigabitEthernet2
 ip address 192.0.2.42 255.255.255.252
 no shutdown
exit
router ospf 1
 router-id 10.255.0.7
 network 10.255.0.7 0.0.0.0 area 0
 passive-interface Loopback0
 network 192.0.2.38 0.0.0.0 area 0
 network 192.0.2.42 0.0.0.0 area 0
exit
router bgp 65067
 bgp router-id 10.255.0.7
 bgp confederation identifier 65467
 bgp confederation peers 65045
 no bgp default ipv4-unicast
 neighbor 10.255.0.5 remote-as 65045
 neighbor 10.255.0.5 update-source Loopback0
 neighbor 10.255.0.5 ebgp-multihop 2
 neighbor 10.255.0.6 remote-as 65067
 neighbor 10.255.0.6 update-source Loopback0
 address-family ipv4 unicast
  no auto-summary
  neighbor 10.255.0.5 activate
  neighbor 10.255.0.5 next-hop-self
  neighbor 10.255.0.6 activate
  neighbor 10.255.0.6 next-hop-self
  network 10.255.0.7 mask 255.255.255.255
 exit-address-family
end

R8

hostname R8
ip cef
interface Loopback0
 ip address 10.255.0.8 255.255.255.255
exit
interface GigabitEthernet1
 ip address 192.0.2.46 255.255.255.252
 no shutdown
exit
interface GigabitEthernet2
 ip address 192.0.2.49 255.255.255.252
 no shutdown
exit
ip route 10.255.0.5 255.255.255.255 192.0.2.45
ip route 10.255.0.9 255.255.255.255 192.0.2.50
end

R9

hostname R9
ip cef
interface Loopback0
 ip address 10.255.0.9 255.255.255.255
exit
interface GigabitEthernet1
 ip address 192.0.2.50 255.255.255.252
 no shutdown
exit
ip route 192.0.2.45 255.255.255.255 192.0.2.49
ip route 10.255.0.5 255.255.255.255 Tunnel0
interface Tunnel0
 ip address 192.0.2.202 255.255.255.252
 tunnel source GigabitEthernet1
 tunnel destination 192.0.2.45
exit
router bgp 4200000009
 bgp router-id 10.255.0.9
 no bgp default ipv4-unicast
 neighbor 10.255.0.5 remote-as 65467
 neighbor 10.255.0.5 update-source Loopback0
 neighbor 10.255.0.5 ebgp-multihop 2
 address-family ipv4 unicast
  no auto-summary
  neighbor 10.255.0.5 activate
  network 10.255.0.9 mask 255.255.255.255
 exit-address-family
end

Open plain-text configurations

The physical outer GRE endpoints are R5 192.0.2.45 and R9 192.0.2.50. Their static /32 routes resolve through R8, so tunnel recursion does not point back into Tunnel0. Inner loopbacks 10.255.0.5 and .9 use the tunnel; BGP is sourced from those loopbacks with multihop 2. Tunnel0 uses 192.0.2.201/30 on R5 and .202/30 on R9. R8 has only connected forwarding and two loopback static routes, never BGP.

The saved solution advertises each internal loopback through its own BGP network statement. OSPF supplies recursive underlay reachability. Border next-hop-self prevents inaccessible external link addresses from becoming hidden forwarding dependencies across the confederation. IPv6 is activated only on ISP/R1 and R1’s AS65023-facing sessions.

Policy solutions in separate stages

Solution: prefix-specific attribute changes

R4: weight on AS65023 imports

ip prefix-list WEIGHT-TARGET seq 5 permit 198.51.100.0/26
route-map REGION-IN permit 10
 match ip address prefix-list WEIGHT-TARGET
 set weight 500
exit
route-map REGION-IN permit 20
exit

router bgp 65045
 address-family ipv4 unicast
  neighbor 192.0.2.21 route-map REGION-IN in
 exit-address-family

R2: local preference on the R1 import

ip prefix-list LP-TARGET seq 5 permit 198.51.100.64/26
route-map PREFER-R2 permit 10
 match ip address prefix-list LP-TARGET
 set local-preference 200
exit
route-map PREFER-R2 permit 20
exit

router bgp 65023
 address-family ipv4 unicast
  neighbor 192.0.2.9 route-map PREFER-R2 in
 exit-address-family

R4# clear ip bgp 192.0.2.21 soft in
R2# clear ip bgp 192.0.2.9 soft in

Each route map has a passthrough clause so unrelated prefixes remain. R4’s weight is local; R2’s LOCAL_PREF travels inside AS65023. The route maps target different routers and do not overwrite each other.

Solution: community scope and upstream allowlist

R1

ip prefix-list SCOPED seq 5 permit 198.51.100.128/26
route-map SCOPE-OUT permit 10
 match ip address prefix-list SCOPED
 set community no-advertise additive
exit
route-map SCOPE-OUT permit 20
exit
ip prefix-list REGIONAL-ONLY seq 5 permit 10.255.0.0/24 ge 32 le 32

router bgp 65001
 address-family ipv4 unicast
  neighbor 192.0.2.10 send-community
  neighbor 192.0.2.14 send-community
  neighbor 192.0.2.6 send-community
  neighbor 192.0.2.10 route-map SCOPE-OUT out
  neighbor 192.0.2.14 route-map SCOPE-OUT out
  neighbor 192.0.2.6 route-map SCOPE-OUT out
  neighbor 192.0.2.1 prefix-list REGIONAL-ONLY out
 exit-address-family

R1# clear ip bgp 192.0.2.10 soft out
R1# clear ip bgp 192.0.2.14 soft out
R1# clear ip bgp 192.0.2.6 soft out
R1# clear ip bgp 192.0.2.1 soft out

R1 uses .10 toward R2, .14 toward R3, .6 toward R4 and .1 toward the ISP. The sample regional /32s are private lab infrastructure; a real public boundary would use authorized public customer space instead.

Solution: a reversible route filter on R9

ip prefix-list R9-IN seq 5 deny 198.51.100.0/26
ip prefix-list R9-IN seq 10 permit 0.0.0.0/0 le 32

router bgp 4200000009
 address-family ipv4 unicast
  neighbor 10.255.0.5 prefix-list R9-IN in
 exit-address-family

R9# clear ip bgp 10.255.0.5 soft in

R9# show ip bgp 198.51.100.0/26
% Network not in table

router bgp 4200000009
 address-family ipv4 unicast
  no neighbor 10.255.0.5 prefix-list R9-IN in
 exit-address-family

R9# clear ip bgp 10.255.0.5 soft in

Detach the filter to restore the prefix. The four-byte ASN and tunnel transport do not need changing.

Apply the scope change after checking the attribute exercises: No Advertise intentionally removes its /26 beyond R2/R3/R4. A later absent route must be interpreted in light of that deliberate policy.

Acceptance checks and expected evidence

R9# show ip bgp summary
BGP router identifier 10.255.0.9, local AS number 4200000009
Neighbor       V      AS  State/PfxRcd
10.255.0.5     4   65467  12

The count is illustrative and changes with policy; the acceptance condition is an established session and the intended route set, not a fixed number.

R4# show ip bgp 198.51.100.0/26
BGP routing table entry for 198.51.100.0/26
  65023 65001 64496 via 192.0.2.21
    weight 500, valid, external, best
  65001 64496 via 192.0.2.5
    weight 0, valid, external

R3# show ip bgp 198.51.100.64/26
BGP routing table entry for 198.51.100.64/26
  65001 64496 via 10.255.0.2
    localpref 200, valid, internal, best
  65001 64496 via 192.0.2.13
    localpref 100, valid, external

R1# show bgp ipv6 unicast 2001:db8:ffff::10/128
BGP routing table entry for 2001:db8:ffff::10/128
  64496 via 2001:db8:0:10::2, valid, external, best

Also test return traffic using explicit sources, inspect the IP forwarding table and verify that the scoped prefix reaches R2/R3/R4 but not R9. R4’s weight and R2’s LOCAL_PREF affect different decisions.

Faults, diagnosis and restoration

Independent fault	Evidence to inspect	Restore
Remove R5’s static outer endpoint route	Tunnel recursion and endpoint reachability.	Restore the saved /32 via R8, not via Tunnel0.
Remove a confederation peer declaration	OPEN remote-AS expectation and session state.	Restore identifier/member settings consistently.
Withdraw one redundant R1 regional link	Remaining BGP path and IP route; actual traffic loss.	Restore interface and wait for convergence.
Remove next-hop-self at one border	Received path versus recursive reachability.	Restore the neighbor’s next-hop treatment.
Deny a prefix on R9	Accepted BGP table versus upstream advertisements.	Detach that filter and refresh the one peer.

Restore the solved core or your saved checkpoint after each independent fault. The pages and consistency checks do not certify a live router run. Record image versions, exact outputs and packet loss when you execute the lab.

Key Takeaways

Build and verify underlay before BGP policy.
The confederation identifier differs from member ASNs.
Tunnel endpoints must not recurse into their own tunnel.
Weight, LOCAL_PREF and communities have different scopes.
Accept a lab result only after checking routes and forwarding in both directions.

Protocol and command references

BGP specification · Confederations · Multiprotocol extensions · Router-symbol attribution.

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