Cisco Troubleshooting BGP EVPN VXLAN: Comprehensive Guide to Unicast, Multicast & Broadcast Issues (EN)

Troubleshooting Scenarios for BGP EVPN VXLAN

Troubleshooting BGP EVPN VXLAN Troubleshooting Scenarios for BGP EVPN VXLAN, on page 1 Troubleshooting Broadcast, Unkown Unicast, Multicast Traffic Forwarding, on page 2 Troubleshooting Unicast Forwarding Between VTEPs in the Same VLAN Through a Layer 2 VNI, on page 6 Troubleshooting Unicast Forwarding Between VTEPS in Different VLANs Through a Layer 3 VNI, on page 18 Troubleshooting Unicast Forwarding Between a VXLAN Network and an IP Network, on page 31 Troubleshooting Tenant Routed Multicast, on page 34 Troubleshooting Scenarios for BGP EVPN VXLAN This document provides information about the various troubleshooting scenarios that are applicable to BGP EVPN VXLAN and how to troubleshoot each scenario.

In this troubleshooting document, comments have been added at the end of certain lines of the outputs of show commands. This has been done to highlight or explain a specific aspect of that line of output. If a comment begins in a new line, then it refers to the line of output that precedes the comment. The following notation has been used throughout the document to highlight the comments inside the outputs of show commands: Text highlighted in this format inside a command's output represents a comment. This is done for explanation purpose only and is not part of the command's output.

The following is a sample EVPN VXLAN topology with two access facing VTEPs (VTEP 1 and VTEP 2) and a border leaf VTEP connected in a VXLAN network through an EVPN route reflector. Each of the access facing VTEPs has two host devices connected to it and the border leaf VTEP is connected to an external IP network. All the troubleshooting scenarios in this document are explained using this topology. Troubleshooting BGP EVPN VXLAN 1

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Troubleshooting Broadcast, Unkown Unicast, Multicast Traffic Forwarding

Figure 1: EVPN VXLAN Topology The following are the various troubleshooting scenarios that apply to BGP EVPN VXLAN for the topology illustrated in the figure above: Scenario 1: Troubleshooting Broadcast, Unknown Unicast, Multicast traffic Forwarding Scenario 2: Troubleshooting Unicast Forwarding Between VTEPs in the Same VLAN Through a Layer 2 VNI Scenario 3: Troubleshooting Unicast Forwarding Between VTEPS in Different VLANs Through a Layer 3 VNI Scenario 4:

Troubleshooting Unicast Forwarding Between a VXLAN Network and an IP Network Troubleshooting Broadcast, Unkown Unicast, Multicast Traffic Forwarding This scenario might occur when host device 2 attempts to learn the ARP for host device 3 in Figure 1: EVPN VXLAN Topology, on page 2 . Perform the checks listed in the following table before troubleshooting BUM traffic forwarding: Troubleshooting BGP EVPN VXLAN Troubleshooting Broadcast, Unkown Unicast, Multicast Traffic Forwarding Troubleshooting BGP EVPN VXLAN 2

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Troubleshooting Broadcast, Unkown Unicast, Multicast Traffic Forwarding

Table 1: Scenario 1: Broadcast, Unkown Unicast, Multicast traffic Forwarding BUM traffic is forwarded by a VTEP into the VXLAN Core using multicast routing. In order to follow the path of an ARP broadcast packet, you need to identify the multicast group that needs to be used to send this traffic into the core and to the other VTEPs. BUM traffic first arrives at the local Layer 2 interface. The traffic is encapsulated here and sent out using the multicast group that is sourced from the VXLAN Loopback interface. Underlay multicast needs to be fully configured before troubleshooting BUM traffic forwarding for EVPN VXLAN.

Note To troubleshoot EVPN VXLAN BUM traffic forwarding, follow these steps: 1. Determine the MAC Address of the Local Host Device and the Multicast Group Used for ARP Tunneling, on page 3 2. Set Up Embedded Capture Towards the Core-Facing Interface, on page 4 3. Ping the Remote Host Device, on page 4 4. Verify that an ARP Request Has Been Received and a Multicast Route Has Been Built, on page 4 5. Confirm the Presence of ARP Request Replies in Embedded Capture, on page 5 6. Verify that the Encapsulated ARP Request is Leaving in a Multicast Group to a VXLAN UDP Destination Port, on page 5 7.

Verify that the ARP Reply from Core Interface is Encapsulated in Unicast to a VXLAN UDP Destination Port, on page 6 Determine the MAC Address of the Local Host Device and the Multicast Group Used for ARP Tunneling The following examples show how to verify the MAC address of the local host device and the multicast group that is used for tunneling the ARP broadcast request: Troubleshooting BGP EVPN VXLAN Troubleshooting Broadcast, Unkown Unicast, Multicast Traffic Forwarding Check to be Performed Steps to Follow Is the packet of broadcast type? Check if the packet is a broadcast packet, such as an ARP broadcast packet. Are the hosts in the same subnet or in different subnets?

Perform any of the following steps: • Check the host device. • Check the SVI configuration on the VTEP. Has the remote MAC address been learned for unknown unicast traffic? Run the show platform software fed switch active matm macTable vlan vlan-id command in privileged EXEC mode on the local VTEP and check if the MAC address of the remote host device is displaed in the output. If not, you have not yet learned the remote host device and it needs to be resolved. Troubleshooting BGP EVPN VXLAN 3

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Troubleshooting Broadcast, Unkown Unicast, Multicast Traffic Forwarding

VTEP-1# show mac address-table address 005f.8602.10c6 Mac Address Table ------------------------------------------- Vlan Mac Address Type Ports ---- ----------- -------- ----- 10 005f.8602.10c6 DYNAMIC Tw1/0/1 MAC address of 10.10.10.11 is learnt here VTEP-1# show run int nve 1 interface nve1 no ip address source-interface Loopback999 host-reachability protocol bgp member vni 10001 mcast-group 239.10.10.10 Group is mapped to the VNI under NVE VTEP-1# show run | s vlan conf vlan configuration 10 VTEP-1# show l2vpn evpn evi EVI VLAN Ether Tag L2 VNI Multicast Pseudoport ----- ----- ---------- --------- ------------- ------------------ 10 10 0 10001 239.10.10.10 Tw1/0/1:10 EVPN instance 10 is mapped to VLAN 10 and VNI 10001 member evpn-instance 10 vni 10001 VNI mapped under VLAN 10 (Using multicast group 239.10.10.10 for Broadcast ecap tunnel) Set Up Embedded Capture Towards the Core-Facing Interface The following example shows how to set up embedded capture towards the core-facing interface:

On a production network, use this command with a filter. Note VTEP-1# show monitor capture 1 parameter monitor capture 1 interface TwoGigabitEthernet1/0/2 BOTH monitor capture 1 match any monitor capture 1 buffer size 100 monitor capture 1 limit pps 1000 Ping the Remote Host Device The following example shows how to ping the remote host device: VTEP-1-HOST# ping 10.10.10.12 sourced from Host machine 10.10.10.11 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.10.10.12, timeout is 2 seconds: ..!!!

Verify that an ARP Request Has Been Received and a Multicast Route Has Been Built This step is to verify that there is multicast reachability between VTEPs using standard multicast validation. Underly multicast state is not permanent. If it is not in use, these S,G states will expire. Troubleshooting BGP EVPN VXLAN Troubleshooting Broadcast, Unkown Unicast, Multicast Traffic Forwarding Troubleshooting BGP EVPN VXLAN 4

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