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[QFX] Static routes pointing to subnets behind Qfabric-RSNG is not supported



Article ID: KB31289 KB Last Updated: 06 Jul 2017Version: 2.0

Transit traffic cannot be sent to another layer-3 device, if it is physically connected on the RSNG or SNG. 


NNG--Qfabric--RSNG1--ae44 (xe-0/0/44,1/0/44)======Layer-3-Switch(vlan-10; ip-address:- (Gateway on layer-3 switch)

There are a few subnets connected behind the Layer-3 Switch.

IRB configured on the Qfabric:

unit 10 {
     description "to layer-3 switch";
     family inet {

  • Hosts connected on the layer-3 device cannot reach the qfabric vLAN-10 IP address and vice-versa
  • Hosts can only reach or ping to the layer-3 device.
  • Same status on the qfabric side and Qfabric can only ping to the layer-3 address but not to the hosts.

The following symptoms were observed:

  1. Ping connectivity between the end devices fail.
  2. In the test, ping works from qfabric to the layer-3 switch and from the host to the layer-3 switch.
  3. ARP entry shows as "hold" status on the qfabric NNG.
  4. ARP entry may show complete if checked from the RSNG and DG.

Topology used for verification:
[Qfabric]---------------------[Qfx5100] irb.10 and irb.20


Ping to irb.10 on QFX5100 connected to Qfabric RSNG is successful:

Ping from Qfabric:

root@JTAC-QF02# run ping routing-instance JTAC
64 bytes from icmp_seq=0 ttl=64 time=20986 micro seconds
64 bytes from icmp_seq=1 ttl=64 time=21645 micro seconds


Not able to ping irb.20 ( on QFX5100:
root@JTAC-QF02# run ping routing-instance JTAC
error: from NW-NG-0: Read timed out

QFX5100 output :
root# run show interfaces terse irb
Interface Admin Link Proto Local Remote
irb up up
irb.10 up up inet
irb.20 up up inet

Qfabric NW-NG-0 Output:

qfabric-admin@NW-NG-0> show route forwarding-table
Routing table: JTAC---qfabric.inet
Destination Type RtRef Next hop Type Index NhRef Netif
default perm 0 rjct 2056 1 dest 0       hold 2079 3 vlan.10 user 0       hold 2079 3 vlan.20 >>>>>>>>||$ hold

qfabric-admin@NW-NG-0> show route forwarding-table destination extensive

Routing table: JTAC---qfabric.inet [Index 6]

Route type: destination
Route reference: 0 Route interface-index: 65
Multicast RPF nh index: 0
Flags: sent to PFE
Next-hop type: composite Index: 1961 Reference: 3
Load Balance Label: Push 5, None
Next-hop type: indirect Index: 131142 Reference: 2
Next-hop type: Push 23, Push 45(top) Index: 1845 Reference: 6
Load Balance Label: None
Next-hop interface: dcfabric.0

Route type: destination
Route reference: 0 Route interface-index: 107
Multicast RPF nh index: 0
Flags: none
Next-hop type: hold Index: 2000 Reference: 8
Next-hop interface: vlan.10

This works as per design. In Qfabric, Layer-3 behind RSNG is NOT supported. Only NNG is responsible for L2/L3 network-facing protocols. SNG and RSNG handles host-facing protocols such as LACP,LLDP, ARP, DCBX, etc. 


 As a workaround, move the connection of the Layer-3 switch from RSNG to NNG.

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