This article explains why protocols running over Generic Routing Encapsulation (GRE) go down once the inet family is removed from GRE. This is expected behavior.
R1(10.1.1.1)-----------------------------------------------(10.1.1.2)R2
====================GRE=====================
<-----------------------OSPF/ISIS over GRE---------------------------->
set chassis fpc 1 pic 0 tunnel-services bandwidth 1g
set chassis fpc 1 pic 2 tunnel-services bandwidth 1g
set interfaces ge-3/0/1 vlan-tagging
set interfaces ge-3/0/1 unit 10 vlan-id 10
set interfaces ge-3/0/1 unit 10 family inet address 10.1.1.2/30
set interfaces ge-3/0/1 unit 10 family iso
set interfaces gr-1/2/10 unit 200 tunnel source 10.1.1.2
set interfaces gr-1/2/10 unit 200 tunnel destination 10.1.1.1
set interfaces gr-1/2/10 unit 200 family inet
set interfaces gr-1/2/10 unit 200 family iso
set interfaces lo0 unit 0 family iso address 39.246f.0010.9109.0000.0001.0900.9005.2042.0201.00
set protocols isis interface gr-1/2/10.200 level 2 disable
lab@mx80-2# run show interfaces terse | match gr-
gr-1/2/10 up up
gr-1/2/10.200 up up inet
[edit]
lab@mx80-2# run show isis adjacency
Interface System L State Hold (secs) SNPA
gr-1/2/10.200 mx480-7-re0 1 Up 25
Before Deactivating Family INET on gr interface:
TAZ-TBB-0(pfe-bng1-l vty)# show ifl brief Index Name Type Encapsulation Flags RT Index Channel FNP status ----- -------------------- ------------- -------------- ------ -------- ---------- ..... 331 gr-1/3/10.0 GRE-over-IP GRE 0x000000000000c010 0 0 TAZ-TBB-0(pfe-bng1-l vty)# show route ip IPv4 Route Table 0, default.0, 0x0: Destination NH IP Addr Type NH ID Interface default Reject 36 RT-ifl 0 0.0.0.0 Discard 34 RT-ifl 0 ..... 10.1.1.1.10.1.1.2.47/72 Local 564 RT-ifl 331 gr-1/3/10.0 ifl 331 Decap Route .... TAZ-TBB-0(pfe-bng1-l vty)# show topology iff ip 331 Topology: (ih-iff 331) Flavor: ih-iff (4), Refcount 1, Flags 0x1 Addr: 0x495b86c0, Next: 0x0, Context 0x43ee08b0 Link 0: 08776aa0:00010000, Offset 10, Next: 00000000:00000000 Link 1: 00000000:00000000, Offset 10, Next: 00000000:00000000 Link 2: 00000000:00000000, Offset 10, Next: 00000000:00000000 Link 3: 00000000:00000000, Offset 10, Next: 00000000:00000000 Topology Neighbors: iff-in(331)-> (ih-iff 331) Topology: (oh-iff 331) Flavor: oh-iff (5), Refcount 1, Flags 0x1 Addr: 0x495b8740, Next: 0x0, Context 0x43ee08b0 Link 0: e0000c60:0052c5c4, Offset 12, Next: 00000000:00000000 Link 1: 00000000:00000000, Offset 12, Next: 00000000:00000000 Link 2: 00000000:00000000, Offset 12, Next: 00000000:00000000 Link 3: 00000000:00000000, Offset 12, Next: 00000000:00000000 Topology Neighbors: iff-out(331)-> (oh-iff 331)
After deactivating family INET on gr interface:
lab@mx80-2# delete interfaces gr-1/2/10 unit 200 family inet
lab@mx80-2# run show interfaces terse | match gr-
gr-1/2/10 up up
gr-1/2/10.200 up up iso
GRE shows up but is not able to pass traffic.
lab@mx80-2# run show isis adjacency
Interface System L State Hold (secs) SNPA
gr-1/2/10.200 mx480-7-re0 1 Down 0 .
TAZ-TBB-0(pfe-bng1-l vty)# show topology iff ip 331
No family (IPv4) configured for ifl 331
TAZ-TBB-0(pfe-bng1-l vty)# show topology route ip ifl 331
No family (IPv4) configured for ifl 331
IPv4 is in broken state for GRE as shown in above command, as there is no family configured for ifl 331 (gr interface) for the incoming ISIS packets encapsulated in IP header.
For this reason, the packets will not be hitting the GR interface.
L2 CSNP packets are getting dropped in the kernel when the inet family is deactivated on the GR interface. When a packet is sent for decapsulation, the GRE code checks for ‘inet’ family on the IFL. Since the deactivation deletes the family, the GRE code discards the packet by ticking noroute counter.
After the inet family is removed from the GRE, there will not be any IFF (IFL) associated in PFE for forwarding traffic. This is an expected behavior.