Cross-Connect Configuration¶

This section covers Layer 2 Cross-Connect (L2 xconnect) and Layer 3 Cross-Connect (L3XC) configuration in FloofOS for direct interface-to-interface forwarding.

Overview¶

Cross-connect provides direct packet forwarding between interfaces, bypassing normal switching or routing decisions:

Feature	Layer	Description
L2 xconnect	Layer 2	Direct L2 forwarding between two interfaces
L3XC	Layer 3	Force traffic to specific next-hop, bypass FIB

Layer 2 Cross-Connect (L2 xconnect)¶

L2 xconnect creates a point-to-point Layer 2 connection between two interfaces. All traffic received on one interface is forwarded directly to the other interface without MAC learning or bridge domain membership.

Use Cases¶

Pseudowire services - Transparent L2 connectivity for customers
MPLS L2VPN termination - Connect customer ports to MPLS pseudowires
Transparent bridging - Simple two-port bridging without MAC table
Traffic mirroring - Forward traffic between interfaces
Bypass scenarios - Direct forwarding for specific ports

L2 xconnect vs Bridge Domain¶

Aspect	L2 xconnect	Bridge Domain
Interfaces	Exactly 2	Multiple
MAC Learning	No	Yes
Flooding	No	Yes
Performance	Higher	Lower
Use Case	Point-to-point	Multi-access

Configure L2 Cross-Connect¶

Create L2 xconnect¶

Syntax:

set interface l2 xconnect <interface1> <interface2>

Parameters:

Parameter	Description
`<interface1>`	First interface in the cross-connect pair
`<interface2>`	Second interface in the cross-connect pair

Example:

set interface l2 xconnect GE1/0/1 GE1/0/2
commit

This creates a bidirectional L2 cross-connect between GE1/0/1 and GE1/0/2.

Bidirectional Configuration

L2 xconnect is bidirectional. You only need to configure it once - traffic flows both ways automatically.

Remove L2 xconnect¶

To remove an interface from L2 xconnect and return it to Layer 3 mode:

Syntax:

set interface l3 <interface>

Example:

set interface l3 GE1/0/1
set interface l3 GE1/0/2
commit

Show L2 xconnect Status¶

Show All Cross-Connects¶

show l2patch

Displays all active L2 cross-connect pairs.

Show Interface Mode¶

show mode [<interface>]

Displays the L2 mode (l3, xconnect, bridge) for each interface.

L2 xconnect with VLAN Tag Rewrite¶

You can combine L2 xconnect with VLAN tag manipulation for advanced scenarios.

Tag Rewrite Operations¶

Operation	Description
`push`	Add VLAN tag
`pop`	Remove VLAN tag
`translate`	Replace VLAN tag

Configure Tag Rewrite¶

Syntax:

set interface l2 tag-rewrite <interface> {push|pop|translate} [dot1q <vlan-id>] [dot1ad <vlan-id>]

Example - Pop outer tag:

set interface l2 tag-rewrite GE1/0/1 pop 1
commit

Example - Push VLAN tag:

set interface l2 tag-rewrite GE1/0/1 push dot1q 100
commit

Example - Translate VLAN:

set interface l2 tag-rewrite GE1/0/1 translate 1-1 dot1q 200
commit

Configuration Examples¶

Example 1: Simple Two-Port Cross-Connect¶

Connect two customer ports transparently.

                Customer A                    Customer A
                  Site 1                       Site 2
                    │                            │
                    ▼                            ▼
              ┌──────────┐                ┌──────────┐
              │ GE1/0/1  │◄── xconnect ──►│ GE1/0/2  │
              └──────────┘                └──────────┘
                         FloofOS Router

Configuration:

# Create L2 xconnect between customer ports
set interface state GE1/0/1 up
set interface state GE1/0/2 up
set interface l2 xconnect GE1/0/1 GE1/0/2
commit

# Verify
show mode GE1/0/1 GE1/0/2

Example 2: VLAN-to-VLAN Cross-Connect¶

Connect two different VLANs with tag translation.

            VLAN 100                         VLAN 200
                │                                │
                ▼                                ▼
          ┌──────────┐                    ┌──────────┐
          │GE1/0/1.100│◄── xconnect ────►│GE1/0/2.200│
          └──────────┘   (translate)      └──────────┘

Configuration:

# Create sub-interfaces
create sub-interfaces GE1/0/1 100
create sub-interfaces GE1/0/2 200

# Enable interfaces
set interface state GE1/0/1 up
set interface state GE1/0/2 up
set interface state GE1/0/1.100 up
set interface state GE1/0/2.200 up

# Create L2 xconnect
set interface l2 xconnect GE1/0/1.100 GE1/0/2.200

commit

Example 3: Cross-Connect to VXLAN Tunnel¶

Extend L2 connectivity over VXLAN tunnel (pseudowire over IP).

         Local Port                      VXLAN Tunnel
             │                                │
             ▼                                ▼
       ┌──────────┐                    ┌─────────────┐
       │ GE1/0/1  │◄── xconnect ────►│vxlan_tunnel0│
       └──────────┘                    └─────────────┘
                                              │
                                              ▼
                                        Remote Site

Configuration:

# Create VXLAN tunnel
create vxlan tunnel src 10.0.0.1 dst 10.0.0.2 vni 10001 instance 0

# Enable interfaces
set interface state GE1/0/1 up
set interface state vxlan_tunnel0 up

# Create L2 xconnect between local port and VXLAN tunnel
set interface l2 xconnect GE1/0/1 vxlan_tunnel0

commit

# Verify
show l2patch

Example 4: Multi-Tenant Pseudowire Service¶

Multiple customers with isolated cross-connects.

# Customer A - VLAN 100 to VXLAN VNI 10100
create sub-interfaces GE1/0/1 100
create vxlan tunnel src 10.0.0.1 dst 10.0.0.2 vni 10100 instance 0
set interface state GE1/0/1.100 up
set interface state vxlan_tunnel0 up
set interface l2 xconnect GE1/0/1.100 vxlan_tunnel0

# Customer B - VLAN 200 to VXLAN VNI 10200
create sub-interfaces GE1/0/1 200
create vxlan tunnel src 10.0.0.1 dst 10.0.0.3 vni 10200 instance 1
set interface state GE1/0/1.200 up
set interface state vxlan_tunnel1 up
set interface l2 xconnect GE1/0/1.200 vxlan_tunnel1

# Customer C - VLAN 300 to VXLAN VNI 10300
create sub-interfaces GE1/0/1 300
create vxlan tunnel src 10.0.0.1 dst 10.0.0.4 vni 10300 instance 2
set interface state GE1/0/1.300 up
set interface state vxlan_tunnel2 up
set interface l2 xconnect GE1/0/1.300 vxlan_tunnel2

commit

# Verify all cross-connects
show l2patch

Example 5: Cross-Connect with QinQ¶

Double-tagged customer traffic.

# Create QinQ sub-interface (outer 100, inner 200)
create sub-interfaces GE1/0/1 100 inner-dot1q 200

# Create xconnect to another port
set interface state GE1/0/1.100.200 up
set interface state GE1/0/2 up
set interface l2 xconnect GE1/0/1.100.200 GE1/0/2

commit

Layer 3 Cross-Connect (L3XC)¶

L3XC forces traffic matching specific criteria to a predetermined next-hop, bypassing the normal FIB lookup. This is useful for traffic steering and policy-based routing.

Use Cases¶

Traffic steering - Force specific traffic to alternate path
Service chaining - Direct traffic through middleboxes
Policy-based routing - Bypass normal routing for specific flows
Load balancing - Distribute traffic across multiple paths

Configure L3XC¶

Syntax:

l3xc add <interface> via <next-hop-ip> <outgoing-interface>

Parameters:

Parameter	Description
`<interface>`	Input interface for L3XC
`<next-hop-ip>`	Forced next-hop IP address
`<outgoing-interface>`	Outgoing interface

Example:

l3xc add GE1/0/1 via 10.0.0.2 GE1/0/2
commit

Delete L3XC¶

Syntax:

l3xc del <interface>

Example:

l3xc del GE1/0/1
commit

Show L3XC¶

show l3xc

L3XC Configuration Examples¶

Example 1: Force Traffic to Specific Gateway¶

Force all traffic from a specific interface to use alternate gateway.

# All traffic from GE1/0/1 goes to gateway 10.0.0.254 via GE1/0/2
l3xc add GE1/0/1 via 10.0.0.254 GE1/0/2
commit

Example 2: Service Chaining Through Firewall¶

Direct traffic through a firewall appliance.

                    Firewall
                   10.1.1.1
                      │
              ┌───────┴───────┐
              │    GE2/0/0    │
              │               │
     Traffic  │   FloofOS     │
    ─────────►│               │
      GE1/0/1 │    L3XC      │
              └───────────────┘

Configuration:

# Force all traffic from GE1/0/1 to firewall at 10.1.1.1
l3xc add GE1/0/1 via 10.1.1.1 GE2/0/0
commit

Best Practices¶

L2 xconnect¶

Recommendation	Description
Interface State	Ensure both interfaces are `up` before creating xconnect
MTU Matching	Use same MTU on both xconnect interfaces
Monitoring	Monitor interface counters for traffic verification
Documentation	Document all xconnect pairs for operations

L3XC¶

Recommendation	Description
Use Sparingly	L3XC bypasses routing - use only when necessary
Next-hop Reachable	Ensure next-hop is directly connected or ARP-resolvable
Monitor Traffic	Verify traffic is flowing as expected

Troubleshooting¶

Common Issues¶

Issue	Possible Cause	Solution
No traffic flow	Interface down	Check `show interface` status
One-way traffic	Asymmetric xconnect	Verify xconnect on both interfaces
MTU issues	MTU mismatch	Match MTU on both interfaces
Tagged traffic issues	Missing tag rewrite	Configure appropriate tag-rewrite

Verification Commands¶

# Check xconnect configuration
show l2patch
show mode

# Check interface status
show interface GE1/0/1
show interface GE1/0/2

# Check interface counters
show interface

# Check L3XC
show l3xc

Cross-Connect Configuration¶

Overview¶

Layer 2 Cross-Connect (L2 xconnect)¶

Use Cases¶

L2 xconnect vs Bridge Domain¶

Configure L2 Cross-Connect¶

Create L2 xconnect¶

Remove L2 xconnect¶

Show L2 xconnect Status¶

Show All Cross-Connects¶

Show Interface Mode¶

L2 xconnect with VLAN Tag Rewrite¶

Tag Rewrite Operations¶

Configure Tag Rewrite¶

Configuration Examples¶

Example 1: Simple Two-Port Cross-Connect¶

Example 2: VLAN-to-VLAN Cross-Connect¶

Example 3: Cross-Connect to VXLAN Tunnel¶

Example 4: Multi-Tenant Pseudowire Service¶

Example 5: Cross-Connect with QinQ¶

Layer 3 Cross-Connect (L3XC)¶

Use Cases¶

Configure L3XC¶

Delete L3XC¶

Show L3XC¶

L3XC Configuration Examples¶

Example 1: Force Traffic to Specific Gateway¶

Example 2: Service Chaining Through Firewall¶

Best Practices¶

L2 xconnect¶

L3XC¶

Troubleshooting¶

Common Issues¶

Verification Commands¶

Related Documentation¶

External References¶