labroot@QFX1# show route forwarding-table destination 5.223.48.38
Enabled protocols: Bridging, 
Destination    Type RtRef Next hop          Type Index  NhRef Netif
5.223.48.38/32   dest   2 5.223.48.38       hold   2122   3 irb.606
5.223.48.38/32   dest   1 f4:bf:a8:14:64:a5 ucst   2119   2 xe-0/0/85.606

• Here 5.223.48.39/31 is supernet of  5.223.48.5/20 hence overlapping is seen in the above examples. By design, Subnets should not overlap .​​​​​​

• Due to the above overlapping of subnet configuration, though the routing table has a single next-hop, the forwarding table has two entries and one of them [here irb.606] is stuck in a hold state which should not happen.

• The hold state of a route in the forwarding table indicates the next hop is being resolved, so it is an intermediate state but here the entry is stuck with the hold state because of the overlapping subnet. This is making the directly connected IP address not reachable.

• Traffic will hit this direct next hop and trigger ARP over the /31 segment.​​​​​​
• If the interface flaps and the /31 next-hop is reinstalled, it will be placed below the /20.
• The lookup will hit the /20 subnet and trigger ARP over that VLAN, which doesn’t get resolved because the IP lives in a different segment. No further processing is done because the destination IP falls within a directly connected subnet.
• The software can’t check for overlapping subnets. Comparing each IP against the others configured in all interfaces would be an exponential task and the commit times would increase too much

• By design, subnets should not overlap. That is, the range of addresses in one subnet should be unique compared to all other subnets.
• In real networks, if two subnets overlap, when a router needs to send a packet to an IP address inside that range of overlapped addresses, the router may forward the packet to the wrong subnet.
• Avoiding overlapping subnets falls under general network designing guidelines and also network admin needs to take care that IPs don’t overlap.

For example, we can use different subnets as below to overcome the subnet issue:

labroot@QFX2> show configuration interfaces xe-0/0/21.606 

vlan-id 606;
 family inet {
 address 5.223.48.38/31 <<<<<

}

labroot@QFX2> show configuration interfaces irb.606 
unit 606 {
  family inet {
address 5.223.0.3/20 {
 vrrp-group 60 {
virtual-address 5.223.0.1 <<<<<<<
preempt;
accept-data;
 }