We can lookup how many routing TCAM entries are programmed in PFE through the below command:
root@EX4500> start shell
root@EX4500:RE:0% cprod -A fpc0 -c "show route ip table"
Example:
We have performed the below test on EX4500 running on 12.2R2 .
Ø When no network routes are installed on the box.
root@EX4500> show route summary
Router ID: 10.230.205.130
inet.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)
Direct: 1 routes, 1 active
Local: 1 routes, 1 active
root@EX4500> show route forwarding-table summary
Routing table: default.inet
Internet:
perm: 5 routes
intf: 2 routes
dest: 3 routes
Routing table: __master.anon__.inet
Internet:
perm: 5 routes
Routing table: default.iso
--------snip------
root@EX4500> start shell
root@EX4500:RE:0% cprod -A fpc0 -c "show route ip table"
Protocol: IPv4
Table Name Table Index (lrid ) # of Routes Bytes FRRP TID
-----------------------------------------------------------------------------------------------
__juniper_private1__.1 1 (0 ) 8 1180 low ----
__juniper_private2__.2 2 (0 ) 5 736 low ----
__master.anon__.3 3 (0 ) 5 736 low ----
default.0 0 (0 ) 9 1328 low ----
Ø When we configured 499 static routes.
root@EX4500> show route summary
Router ID: 10.230.205.130
inet.0: 501 destinations, 501 routes (501 active, 0 holddown, 0 hidden)
Direct: 1 routes, 1 active
Local: 1 routes, 1 active
Static: 499 routes, 499 active
root@EX4500> show route forwarding-table summary
Routing table: default.inet
Internet:
user: 499 routes
perm: 5 routes
intf: 2 routes
dest: 4 routes
Routing table: __master.anon__.inet
Internet:
perm: 5 routes
----------snip--------
root@EX4500> start shell
root@EX4500:RE:0% cprod -A fpc0 -c "show route ip table"
Protocol: IPv4
Table Name Table Index (lrid ) # of Routes Bytes FRRP TID
-----------------------------------------------------------------------------------------------
__juniper_private1__.1 1 (0 ) 8 1180 low ----
__juniper_private2__.2 2 (0 ) 5 736 low ----
__master.anon__.3 3 (0 ) 5 736 low ----
default.0 0 (0 ) 508 75328 low ----
Ø When box learnt 200 new ARP entries.
root@EX4500> show route summary
Router ID: 10.230.205.130
inet.0: 501 destinations, 501 routes (501 active, 0 holddown, 0 hidden)
Direct: 1 routes, 1 active
Local: 1 routes, 1 active
Static: 499 routes, 499 active
root@EX4500> show route forwarding-table summary
Routing table: default.inet
Internet:
user: 499 routes
perm: 5 routes
intf: 2 routes
dest: 204 routes
Routing table: __master.anon__.inet
Internet:
perm: 5 routes
----snip-------
root@EX4500> start shell
root@EX4500:RE:0% cprod -A fpc0 -c "show route ip table"
BSD platform (MPC 8544 processor, 48MB memory, 0KB flash)
Protocol: IPv4
Table Name Table Index (lrid ) # of Routes Bytes FRRP TID
-----------------------------------------------------------------------------------------------
__juniper_private1__.1 1 (0 ) 8 1180 low ----
__juniper_private2__.2 2 (0 ) 5 736 low ----
__master.anon__.3 3 (0 ) 5 736 low ----
default.0 0 (0 ) 709 100044 low ----
So, Host routes (ARP) and network routes share the same space in PFE.
For example
For EX4500 : Max number of IPv4 unicast routes in hardware: 10K.
www.juniper.net/us/en/local/pdf/datasheets/1000322-en.pdf
If System (EX4500) has learnt 8K ARP entries, those 8k host routes will be installed in PFE.
Now the switch can only install remaining 2K IPv4 network routes.
If routing TCAM entry exceeds route table limit, then no new host (ARP) or network route will be installed in TCAM.
The traffic using new routes will not be routed by the switches and will get dropped.