`show bgp l2vpn evpn vni` shows wrong import-rt for L2VNIs with automatic RT

[robinchrist]

Description

The show bgp l2evpn evpn vni commands shows wrong import-rts for L2VNIs with automatic RT:

pve-sdn-test-01# show bgp l2vpn evpn vni
Advertise Gateway Macip: Disabled
Advertise SVI Macip: Disabled
Advertise All VNI flag: Enabled
BUM flooding: Head-end replication
VXLAN flooding: Enabled
Number of L2 VNIs: 5
Number of L3 VNIs: 2
Flags: * - Kernel
  VNI        Type RD                    Import RT                 Export RT                 MAC-VRF Site-of-Origin    Tenant VRF                           
* 1002       L2   10.X.X.X:4        65000:1002                65000:1002                                          vrf_Elim01                           
* 1001       L2   10.X.X.X:2        65000:1001                65000:1001                                          vrf_Elim01                           
* 1003       L2   10.X.X.X:5        65000:1003                65000:1003                                          vrf_Elim01                           
* 2001       L2   10.X.X.X:6        65000:2001                65000:2001                                          vrf_Elim02                           
* 2002       L2   10.X.X.X:8        65000:2002                65000:2002                                          vrf_Elim02                           
* 10001      L3   10.X.X.X:3        65000:10001               65000:10001                                         vrf_Elim01                           
* 10002      L3   10.X.X.X:7        65000:10002               65000:10002                                         vrf_Elim02                          

The configured AS is 65000.

According to a comment in bgp_evpn.c:

/* If using "automatic" RT, we only care about the
 * local-admin sub-field.
 * This is to facilitate using VNI as the RT for EBGP
 * peering too.
 */

If you do show bgp l2vpn evpn import-rt it is shown "correctly" with 0

pve-sdn-test-01# show bgp l2vpn evpn import-rt 
Route-target: 0:2002
List of VNIs importing routes with this route-target:
  2002
Route-target: 0:2001
List of VNIs importing routes with this route-target:
  2001
Route-target: 0:1002
List of VNIs importing routes with this route-target:
  1002
Route-target: 0:1003
List of VNIs importing routes with this route-target:
  1003
Route-target: 0:1001
List of VNIs importing routes with this route-target:
  1001

Version

FRRouting 10.4.1 (pve-sdn-test-01) on Linux(6.17.4-2-pve).
Copyright 1996-2005 Kunihiro Ishiguro, et al.
configured with:
    '--build=x86_64-linux-gnu' '--prefix=/usr' '--includedir=${prefix}/include' '--mandir=${prefix}/share/man' '--infodir=${prefix}/share/info' '--sysconfdir=/etc' '--localstatedir=/var' '--disable-option-checking' '--disable-silent-rules' '--libdir=${prefix}/lib/x86_64-linux-gnu' '--runstatedir=/run' '--disable-maintainer-mode' '--sbindir=/usr/lib/frr' '--with-vtysh-pager=/usr/bin/pager' '--libdir=/usr/lib/x86_64-linux-gnu/frr' '--with-moduledir=/usr/lib/x86_64-linux-gnu/frr/modules' '--disable-dependency-tracking' '--enable-rpki' '--disable-scripting' '--enable-pim6d' '--disable-grpc' '--with-libpam' '--enable-doc' '--enable-doc-html' '--enable-snmp' '--enable-fpm' '--disable-protobuf' '--disable-zeromq' '--enable-ospfapi' '--enable-bgp-vnc' '--enable-multipath=256' '--enable-pcre2posix' '--enable-user=frr' '--enable-group=frr' '--enable-vty-group=frrvty' '--enable-configfile-mask=0640' '--enable-logfile-mask=0640' 'build_alias=x86_64-linux-gnu' 'PYTHON=python3'

How to reproduce

Configure normal EVPN with L2VNIs

Expected behavior

Expected output:

...
  VNI        Type RD                    Import RT                 Export RT                 MAC-VRF Site-of-Origin    Tenant VRF                           
* 1002       L2   10.X.X.X:4        *:1002                        65000:1002                                          vrf_Elim01                           
* 1001       L2   10.X.X.X:2        *:1001                        65000:1001                                          vrf_Elim01                           
* 1003       L2   10.X.X.X:5        *:1003                        65000:1003                                          vrf_Elim01                           
* 2001       L2   10.X.X.X:6        *:2001                        65000:2001                                          vrf_Elim02                           
* 2002       L2   10.X.X.X:8        *:2002                        65000:2002                                          vrf_Elim02                           
* 10001      L3   10.X.X.X:3        *:10001                     65000:10001                                         vrf_Elim01                           
* 10002      L3   10.X.X.X:7        *:10002                     65000:10002                                         vrf_Elim02                          

Wildcard import-RTs should generally be formatted with *:<Local Admin>! The alternative 0:<Local Admin> as in show bgp l2vpn evpn import-rt formatting should be avoided as the meaning is not obvious and rather an internal implementation detail (that the Global Admin is set to 0)

The output of show bgp l2vpn evpn import-rt should also be adjusted:

pve-sdn-test-01# show bgp l2vpn evpn import-rt 
Route-target: *:2002
List of VNIs importing routes with this route-target:
  2002
Route-target: *:2001
List of VNIs importing routes with this route-target:
  2001
Route-target: *:1002
List of VNIs importing routes with this route-target:
  1002
Route-target: *:1003
List of VNIs importing routes with this route-target:
  1003
Route-target: *:1001
List of VNIs importing routes with this route-target:
  1001

Note that 0:<Local Admin> was replaced with *:<Local Admin>

Actual behavior

See above

Additional context

No response

Checklist

• I have searched the open issues for this bug.
• I have not included sensitive information in this report.

[chiragshah6]

The current output is not wrong, the local ASN displayed both for import and export rt. The import RT does not care for the ASN value.
The *:vni is used to display D-VNI (Downstream VNI) import RTs where any ASN with specific L3VNI match.

[robinchrist]

The import RT does not care for the ASN value.

Why is it not displayed as wildcard then?

The *:vni is used to display D-VNI (Downstream VNI) import RTs where any ASN with specific L3VNI match.

That’s… not a thing. Downstream VNI is just the mechanism that allows this to work properly.

Route-Targets are not exclusive to L3VNIs.

RFC9135 Section 5.1:

This route MUST be advertised with two Route Targets, one corresponding to the MAC-VRF of the tenant's subnet and another corresponding to the tenant's IP-VRF.