GRE Tunnel Configuration¶

This section covers Generic Routing Encapsulation (GRE) tunnel configuration in FloofOS.

Overview¶

GRE is a tunneling protocol that encapsulates a wide variety of network layer protocols inside point-to-point links. Common use cases include:

Site-to-site connectivity over public networks
Connecting non-contiguous networks
Encapsulating multicast traffic
Transparent Ethernet Bridging (TEB)

Create GRE Tunnel¶

Syntax¶

create gre tunnel src <local-ip> dst <remote-ip> [instance <n>] [outer-table-id <vrf>] [teb] [erspan <session-id>]

Parameters¶

Parameter	Description
`src`	Local tunnel endpoint IP address
`dst`	Remote tunnel endpoint IP address
`instance`	Tunnel instance number
`outer-table-id`	VRF for outer IP header
`teb`	Transparent Ethernet Bridging mode
`erspan`	ERSPAN session ID for mirroring

Example: Basic GRE Tunnel¶

create gre tunnel src 10.0.0.1 dst 10.0.0.2
set interface state gre0 up
set interface ip address gre0 192.168.100.1/30
commit

View GRE Tunnels¶

show gre tunnel

Delete GRE Tunnel¶

delete gre tunnel src 10.0.0.1 dst 10.0.0.2
commit

GRE Tunnel Types¶

Standard GRE (Layer 3)¶

For routing IP traffic between sites:

create gre tunnel src 10.0.0.1 dst 10.0.0.2
set interface state gre0 up
set interface ip address gre0 192.168.100.1/30
commit

GRE TEB (Transparent Ethernet Bridging)¶

For bridging Layer 2 traffic:

create gre tunnel src 10.0.0.1 dst 10.0.0.2 teb
set interface state gre0 up
set interface l2 bridge gre0 100
commit

ERSPAN (Encapsulated Remote SPAN)¶

For remote traffic mirroring:

create gre tunnel src 10.0.0.1 dst 10.0.0.2 erspan 1

Site-to-Site GRE Example¶

Topology¶

    Site A                                    Site B
    10.0.0.1                                  10.0.0.2
       |                                         |
   +---+---+          GRE Tunnel             +---+---+
   |FloofOS|=============================|FloofOS|
   +---+---+     192.168.100.0/30        +---+---+
       |                                         |
  LAN: 10.1.0.0/24                        LAN: 10.2.0.0/24

Site A Configuration¶

# Create GRE tunnel
create gre tunnel src 10.0.0.1 dst 10.0.0.2
set interface state gre0 up
set interface ip address gre0 192.168.100.1/30

# Route to remote LAN via tunnel
ip route add 10.2.0.0/24 via 192.168.100.2

commit

Site B Configuration¶

# Create GRE tunnel
create gre tunnel src 10.0.0.2 dst 10.0.0.1
set interface state gre0 up
set interface ip address gre0 192.168.100.2/30

# Route to remote LAN via tunnel
ip route add 10.1.0.0/24 via 192.168.100.1

commit

GRE over VRF¶

Create GRE tunnel with outer header in specific VRF:

create gre tunnel src 10.0.0.1 dst 10.0.0.2 outer-table-id 100

Troubleshooting¶

Tunnel Not Working¶

Check tunnel status:
```
show gre tunnel
show interface gre0
```
Verify underlay connectivity:
```
ping 10.0.0.2
```
Check routing:
```
show ip fib
```

MTU Issues¶

GRE adds 24 bytes overhead. Adjust MTU if needed:

set interface mtu 1476 gre0

Command Reference¶

Command	Description
`create gre tunnel src <ip> dst <ip>`	Create GRE tunnel
`create gre tunnel src <ip> dst <ip> teb`	Create GRE TEB tunnel
`create gre tunnel src <ip> dst <ip> erspan <id>`	Create ERSPAN tunnel
`delete gre tunnel src <ip> dst <ip>`	Delete GRE tunnel
`show gre tunnel`	Display GRE tunnels
`set interface state gre<n> up`	Enable tunnel
`set interface ip address gre<n> <ip>`	Assign IP to tunnel