GRE Tunnel Recursive Routing error
GRE Tunnel Recursive Routing error
in the topology above I have created GRE Tunnel between HQ and Branch.
For now it works fine, because the tunnel destination is not the IP address of the tunnel interface on the other end (the tunnel destination is the physical interface on the other end) .However if I Traceroute from HQ to Branch or the other way around, then the traffic will go through ISP.
If ,for instance, on HQ I use Tunnel destination 192.168.13.3 (which is the Branch Tunnel interface IP address), then the tunnel will collapse.
So, I do not know what would be the purpose of the GRE tunnel if traffic does not go through the Tunnel
in the topology above I have created GRE Tunnel between HQ and Branch.
For now it works fine, because the tunnel destination is not the IP address of the tunnel interface on the other end (the tunnel destination is the physical interface on the other end) .However if I Traceroute from HQ to Branch or the other way around, then the traffic will go through ISP.
If ,for instance, on HQ I use Tunnel destination 192.168.13.3 (which is the Branch Tunnel interface IP address), then the tunnel will collapse.
So, I do not know what would be the purpose of the GRE tunnel if traffic does not go through the Tunnel
ISP#sh run
Building configuration...
Current configuration : 1790 bytes
!
! Last configuration change at 22:26:13 CET Sun Feb 25 2018
!
version 15.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname ISP
!
boot-start-marker
boot-end-marker
!
aqm-register-fnf
!
!
no aaa new-model
clock timezone CET 1 0
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
!
!
!
!
!
!
!
!
!
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
redundancy
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Ethernet0/0
ip address 192.168.12.1 255.255.255.0
!
interface Ethernet0/1
ip address 192.168.23.1 255.255.255.0
!
interface Ethernet0/2
no ip address
shutdown
!
interface Ethernet0/3
no ip address
shutdown
!
interface Ethernet1/0
no ip address
shutdown
!
interface Ethernet1/1
no ip address
shutdown
!
interface Ethernet1/2
no ip address
shutdown
!
interface Ethernet1/3
no ip address
shutdown
!
interface Serial2/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/3
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/3
no ip address
shutdown
serial restart-delay 0
!
router rip
version 2
network 192.168.12.0
network 192.168.23.0
no auto-summary
!
ip forward-protocol nd
!
!
no ip http server
no ip http secure-server
!
!
!
!
control-plane
!
!
!
!
!
!
!
!
line con 0
logging synchronous
line aux 0
line vty 0 4
login
transport input none
!
!
end
ISP#
HQ#sh run
Building configuration...
Current configuration : 1967 bytes
!
! Last configuration change at 22:40:16 CET Sun Feb 25 2018
!
version 15.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname HQ
!
boot-start-marker
boot-end-marker
!
aqm-register-fnf
!
!
no aaa new-model
clock timezone CET 1 0
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
!
!
!
!
!
!
!
!
!
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
redundancy
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
ip address 1.1.1.1 255.255.255.255
!
interface Tunnel1
ip address 192.168.13.1 255.255.255.0
tunnel source Loopback0
tunnel destination 192.168.23.3
!
interface Ethernet0/0
ip address 192.168.12.2 255.255.255.0
!
interface Ethernet0/1
no ip address
shutdown
!
interface Ethernet0/2
no ip address
shutdown
!
interface Ethernet0/3
no ip address
shutdown
!
interface Ethernet1/0
no ip address
shutdown
!
interface Ethernet1/1
no ip address
shutdown
!
interface Ethernet1/2
no ip address
shutdown
!
interface Ethernet1/3
no ip address
shutdown
!
interface Serial2/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/3
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/3
no ip address
shutdown
serial restart-delay 0
!
router rip
version 2
network 1.0.0.0
network 192.168.12.0
network 192.168.13.0
no auto-summary
!
ip forward-protocol nd
!
!
no ip http server
no ip http secure-server
!
!
!
!
control-plane
!
!
!
!
!
!
!
!
line con 0
logging synchronous
line aux 0
line vty 0 4
login
transport input none
!
!
end
HQ#
Branch#sh run
Building configuration...
Current configuration : 1971 bytes
!
! Last configuration change at 22:40:52 CET Sun Feb 25 2018
!
version 15.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Branch
!
boot-start-marker
boot-end-marker
!
aqm-register-fnf
!
!
no aaa new-model
clock timezone CET 1 0
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
!
!
!
!
!
!
!
!
!
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
redundancy
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
ip address 3.3.3.3 255.255.255.255
!
interface Tunnel1
ip address 192.168.13.3 255.255.255.0
tunnel source Loopback0
tunnel destination 192.168.12.2
!
interface Ethernet0/0
ip address 192.168.23.3 255.255.255.0
!
interface Ethernet0/1
no ip address
shutdown
!
interface Ethernet0/2
no ip address
shutdown
!
interface Ethernet0/3
no ip address
shutdown
!
interface Ethernet1/0
no ip address
shutdown
!
interface Ethernet1/1
no ip address
shutdown
!
interface Ethernet1/2
no ip address
shutdown
!
interface Ethernet1/3
no ip address
shutdown
!
interface Serial2/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial2/3
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial3/3
no ip address
shutdown
serial restart-delay 0
!
router rip
version 2
network 3.0.0.0
network 192.168.13.0
network 192.168.23.0
no auto-summary
!
ip forward-protocol nd
!
!
no ip http server
no ip http secure-server
!
!
!
!
control-plane
!
!
!
!
!
!
!
!
line con 0
logging synchronous
line aux 0
line vty 0 4
login
transport input none
!
!
end
Branch#
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- ISP, generally, does not participate in routing
- traffic need to be forwarded into tunnel to be tunneled (static or dynamic routing)
- recursive loop happens when tunnel end point is advertised through tunnel which will lead tunnel to collapse (routing instead to point in direction of WAN interface to reach other tunnel end is pointing to tunnel itself (root cause of recursive routing problem))