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06_next_hop: all device configurations

NEXT_HOP, an ISP link that the IGP does not know

Everything below is generated from inventory.yaml, baseline/*.cfg, and scenarios/ + templates/ of this lab. The topology, README and the captured output are in README.md.

How to use it by hand

  1. Import and start the lab (labs/labtool.sh 06_next_hop import and start, or import the .zip in the EVE web UI and start all nodes).
  2. Open each router's console. A fresh router asks Would you like to enter the initial configuration dialog? [yes/no]:. Answer no, press Enter, then type enable.
  3. Type configure terminal and paste that router's block below, then end and write memory.
  4. Routers can be pasted in any order. BGP sessions come up once both ends and the IGP (where the lab has one) are configured.

Management lines. Every block contains a small management section (ip vrf MGMT, FastEthernet0/0 in that VRF, ip route vrf MGMT, username lab, enable secret, line vty). It lets the dashboard and labtool.sh log in over SSH and is not part of the routing design. For a hand-built lab you can leave it out and use only the console. To use SSH you also need crypto key generate rsa modulus 1024 once per router (the bootstrap script does that).

Links

Router A Interface Router B Interface Note
ISP e1/0 EDGE e1/0 172.16.1.0/30 eBGP (not in the IGP)
EDGE e1/1 CORE e1/0 10.0.0.0/30 (OSPF)
CORE e1/1 CLIENT e1/0 10.0.0.4/30 (OSPF)

Devices

Router Role AS Management IP
ISP provider 65001 192.168.99.131
EDGE edge 65000 192.168.99.111
CORE route-reflector 65000 192.168.99.121
CLIENT internal 65000 192.168.99.122

CLIENT

hostname CLIENT
no ip domain lookup
ip domain name lab.local
!
ip vrf MGMT
 rd 65000:99
!
enable secret lab123
username lab privilege 15 secret lab123
!
interface Loopback0
 ip address 10.255.0.20 255.255.255.255
 ip ospf 1 area 0
!
interface FastEthernet0/0
 description === MGMT (Cloud1) ===
 ip vrf forwarding MGMT
 ip address 192.168.99.122 255.255.255.0
 duplex auto
 speed auto
 no shutdown
!
interface Ethernet1/0
 description === to CORE ===
 ip address 10.0.0.6 255.255.255.252
 ip ospf 1 area 0
 ip ospf network point-to-point
 duplex auto
 speed auto
 no shutdown
!
router ospf 1
 router-id 10.255.0.20
 passive-interface Loopback0
!
ip route vrf MGMT 0.0.0.0 0.0.0.0 192.168.99.1
!
router bgp 65000
 bgp router-id 10.255.0.20
 bgp log-neighbor-changes
 no bgp default ipv4-unicast
 neighbor 10.255.0.1 remote-as 65000
 neighbor 10.255.0.1 update-source Loopback0
 address-family ipv4
  neighbor 10.255.0.1 activate
 exit-address-family
!
line vty 0 4
 login local
 transport input ssh
!
end

CORE

hostname CORE
no ip domain lookup
ip domain name lab.local
!
ip vrf MGMT
 rd 65000:99
!
enable secret lab123
username lab privilege 15 secret lab123
!
interface Loopback0
 ip address 10.255.0.1 255.255.255.255
 ip ospf 1 area 0
!
interface FastEthernet0/0
 description === MGMT (Cloud1) ===
 ip vrf forwarding MGMT
 ip address 192.168.99.121 255.255.255.0
 duplex auto
 speed auto
 no shutdown
!
interface Ethernet1/0
 description === to EDGE ===
 ip address 10.0.0.2 255.255.255.252
 ip ospf 1 area 0
 ip ospf network point-to-point
 duplex auto
 speed auto
 no shutdown
!
interface Ethernet1/1
 description === to CLIENT ===
 ip address 10.0.0.5 255.255.255.252
 ip ospf 1 area 0
 ip ospf network point-to-point
 duplex auto
 speed auto
 no shutdown
!
router ospf 1
 router-id 10.255.0.1
 passive-interface Loopback0
!
ip route vrf MGMT 0.0.0.0 0.0.0.0 192.168.99.1
!
router bgp 65000
 bgp router-id 10.255.0.1
 bgp log-neighbor-changes
 no bgp default ipv4-unicast
 neighbor 10.255.0.11 remote-as 65000
 neighbor 10.255.0.11 update-source Loopback0
 neighbor 10.255.0.20 remote-as 65000
 neighbor 10.255.0.20 update-source Loopback0
 address-family ipv4
  neighbor 10.255.0.11 activate
  neighbor 10.255.0.11 route-reflector-client
  neighbor 10.255.0.20 activate
  neighbor 10.255.0.20 route-reflector-client
 exit-address-family
!
line vty 0 4
 login local
 transport input ssh
!
end

EDGE

hostname EDGE
no ip domain lookup
ip domain name lab.local
!
ip vrf MGMT
 rd 65000:99
!
enable secret lab123
username lab privilege 15 secret lab123
!
interface Loopback0
 ip address 10.255.0.11 255.255.255.255
 ip ospf 1 area 0
!
interface FastEthernet0/0
 description === MGMT (Cloud1) ===
 ip vrf forwarding MGMT
 ip address 192.168.99.111 255.255.255.0
 duplex auto
 speed auto
 no shutdown
!
interface Ethernet1/0
 description === eBGP to ISP (AS 65001) ===
 ip address 172.16.1.2 255.255.255.252
 duplex auto
 speed auto
 no shutdown
!
interface Ethernet1/1
 description === to CORE ===
 ip address 10.0.0.1 255.255.255.252
 ip ospf 1 area 0
 ip ospf network point-to-point
 duplex auto
 speed auto
 no shutdown
!
router ospf 1
 router-id 10.255.0.11
 passive-interface Loopback0
!
ip route vrf MGMT 0.0.0.0 0.0.0.0 192.168.99.1
!
router bgp 65000
 bgp router-id 10.255.0.11
 bgp log-neighbor-changes
 no bgp default ipv4-unicast
 neighbor 172.16.1.1 remote-as 65001
 neighbor 10.255.0.1 remote-as 65000
 neighbor 10.255.0.1 update-source Loopback0
 address-family ipv4
  neighbor 172.16.1.1 activate
  neighbor 10.255.0.1 activate
  neighbor 10.255.0.1 next-hop-self
 exit-address-family
!
line vty 0 4
 login local
 transport input ssh
!
end

ISP

hostname ISP
no ip domain lookup
ip domain name lab.local
!
ip vrf MGMT
 rd 65001:99
!
enable secret lab123
username lab privilege 15 secret lab123
!
interface Loopback1
 description === content network ===
 ip address 100.100.100.1 255.255.255.0
!
interface FastEthernet0/0
 description === MGMT (Cloud1) ===
 ip vrf forwarding MGMT
 ip address 192.168.99.131 255.255.255.0
 duplex auto
 speed auto
 no shutdown
!
interface Ethernet1/0
 description === eBGP to EDGE (AS 65000) ===
 ip address 172.16.1.1 255.255.255.252
 duplex auto
 speed auto
 no shutdown
!
ip route vrf MGMT 0.0.0.0 0.0.0.0 192.168.99.1
!
router bgp 65001
 bgp router-id 10.255.1.1
 bgp log-neighbor-changes
 no bgp default ipv4-unicast
 neighbor 172.16.1.2 remote-as 65000
 address-family ipv4
  network 100.100.100.0 mask 255.255.255.0
  neighbor 172.16.1.2 activate
 exit-address-family
!
line vty 0 4
 login local
 transport input ssh
!
end

Scenarios (the change the lab is about)

Scenario 06_next_hop: NEXT_HOP - without next-hop-self the route becomes inaccessible and is never reflected

EDGE stops rewriting NEXT_HOP toward CORE. CORE keeps the path as 172.16.1.1 (inaccessible), because the IGP has no route to the ISP link, and a route reflector only reflects a path it can use, so CLIENT never learns the prefix.

Push to: EDGE (the same lines on each), in configuration mode.

Apply

router bgp 65000
 address-family ipv4
  no neighbor 10.255.0.1 next-hop-self

Roll back

router bgp 65000
 address-family ipv4
  neighbor 10.255.0.1 next-hop-self

Check the result (after about 20 s):

  • CORE# show ip bgp 100.100.100.0/24
  • CORE# show ip route 172.16.1.1
  • CLIENT# show ip bgp 100.100.100.0/24

Commands used to capture the README output

CORE# show ip bgp 100.100.100.0/24
CORE# show ip route 172.16.1.1
CLIENT# show ip bgp 100.100.100.0/24
EDGE# show running-config | include next-hop-self